#25,#26 NAURAL SELECTION

Jean-Baptiste Lamarck proposed that organisms could pass on to their offspring traits that where acquired during their lifetime. This has come to be known as inheritance of acquired characteristics.

On the other hand Charles Darwin recognized the main mechanism for evolution: Natural Selection. Natural Selection is the process by which favorable heritable traits become more common in successive generations of a population and unfavorable heritable traits become less common, due to differential reproduction. That is: given a certain population, those individuals who are more fit to the selective pressure(s) by their habitat (in a given time and space) will leave more descendants than those less fit

In short, Lamarck thought that changes were acquired during the life of a parent organism and then transmitted to their offspring while Darwin deducted that changes were already present in the parent organisms, and that the best adapted to that situation survived to breed, which meant that those genetic changes become common in the following generations.

NATURAL SELECTION:
A process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.

• well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Since the discovery of penicillin in 1928, antibiotics have been used to fight bacterial diseases. Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations. When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them slightly less susceptible. If the exposure to antibiotics is short, these individuals will survive the treatment. This selective elimination of maladapted individuals from a population is natural selection

#23 PLANT DIVISIONS #24 phloem and xylem

Plant divisions

Division	Meaning	Common name	Distinguishing characteristics
Anthocerotophyta	Flower-horn plants	Hornworts	Horn-shaped sporophytes, no vascular system
Bryophyta	Moss plants	Mosses	Persistent unbranched sporophytes, no vascular system
Marchantiophyta	Marchantia plants	Liverworts	Ephemeral unbranched sporophytes, no vascular system
Lycopodiophyta	Wolf foot plants	Clubmosses & Spikemosses	Microphyll leaves, vascular system
Pteridophyta	Fern plants	Ferns & Horsetails	Prothallus gametophytes, vascular system
Pteridospermatophyta	Fern with seeds plant	Seed ferns	Only known from fossils, mostly Devonian, ranking in dispute
Coniferophyta	Sap/pitch plants	Conifers	Cones containing seeds and wood composed of tracheids
Cycadophyta	Palm plants	Cycads	Seeds, crown of compound leaves
Ginkgophyta	Ginkgo plants	Ginkgo, Maidenhair	Seeds not protected by fruit (single species)
Gnetophyta		Gnetophytes	Seeds and woody vascular system with vessels
Anthophyta (or Magnoliophyta)	Flower plant	Flowering plants	Flowers and fruit, vascular system with vessels

Xylem and phloem make up the big transportation system of vascular plants. As you get bigger, it is more difficult to transport nutrients, water, and sugars around your body. You have a circulatory system if you want to keep growing. As plants evolved to be larger, they also developed their own kind of circulatory systems. The main parts you will hear a lot about are called xylem and phloem.
The xylem of a plant is the system of tubes and transport cells that circulates water and dissolved minerals. As a plant, you have roots to help you absorb water. If your leaves need water and they are 100 feet above the ground, it is time to put the xylem into action! Xylem is made of vessels that are connected end to end for the maximum speed to move water around. They also have a secondary function of support. When someone cuts an old tree down, they reveal a set of rings. Those rings are the remains of old xylem tissue, one ring for every year the tree was alive.
The fun never stops in the plant's circulatory system. Most plants have green leaves, where the photosynthesis happens. When those sugars are made, they need to be given to every cell in the plant for energy. Enter phloem. The phloem cells are laid out end-to-end throughout the entire plant, transporting the sugars and other molecules created by the plant. Phloem is always alive. Xylem tissue dies after one year and then develops anew (rings in the tree trunk). What is the best way to think about phloem? Think about sap coming out of a tree. That dripping sap usually comes from the phloem.

#22 HUMAN BODY SYSTEMS

The integumentary system consists of the skin, hair, nails, the subcutaneous tissue below the skin,and assorted glands.The most obvious function of the integumentary system is the protection that the skin gives to underlying tissues. The skin not only keeps most harmful substances out, but also prevents the loss of fluids.

• The skin is often known as "the largest organ in the human body". This applies to exterior surface, as it covers the body, appearing to have the largest surface area of all the organs. Moreover, it applies to weight, as it weighs more than any single internal organ, accounting for about 15 percent of body weight. For the average adult human, the skin has a surface area of between 1.5-2.0 square meters, most of it is between 2-3 mm thick. The average square inch of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than a thousand nerve endings.

. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains 95% of body fat). Fat serves as padding and insulation for the body.

Diagram of the layers of human skin

Functions:

1. Protection: Skin gives an anatomical barrier between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the immune system
2. Sensation: Skin contains a variety of nerve endings that react to heat, cold, touch, pressure, vibration, and tissue injury; see somatosensory system and touch.
3. Heat regulation: The skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss while constricted vessels greatly reduce cutaneous blood flow and conserve heat. Erector pili muscles are significant in animals.

MUSCULAR SYSTEM

The human body contains more than 650 individual muscles which are attached to the skeleton, which provides the pulling power for us to move around. The main job of the muscular system is to provide movement for the body. The muscular system consist of three different types of muscle tissues : skeletal, cardiac, smooth. Each of these different tissues has the ability to contract, which then allows body movements and functions. There are two types of muscles in the system and they are the involuntary muscles, and the voluntary muscles. The muscle in which we are allow to control by ourselves are called the voluntary muscles and the ones we can't control are the involuntary muscles. The heart, or the cardiac muscle, is an example of involuntary muscle.

http://yucky.discovery.com/flash/body/pg000123.html

• The muscles of the body are divided into two main classes: skeletal (voluntary) and smooth (involuntary). Skeletal muscles are attached to the skeleton and move various parts of the body. They are called voluntary because a person controls their use, such as in the flexing of an arm or the raising of a foot. There are about 650 skeletal muscles in the whole human body. Smooth muscles are found in the stomach and intestinal walls, vein and artery walls, and in various internal organs. They are called involuntary muscles because a person generally cannot consciously control them. They are regulated by the autonomic nervous system (part of the nervous system that affects internal organs).

• Another difference between skeletal and smooth muscles is that skeletal muscles are made of tissue fibers that are striated or striped. These alternating bands of light and dark result from the pattern of the filaments  within each muscle cell. Smooth muscle fibers are not striated.

• The cardiac or heart muscle (also called myocardium) is a unique type of muscle that does not fit clearly into either of the two classes of muscle. Like skeletal muscles, cardiac muscles are striated. But like smooth muscles, they are involuntary, controlled by the autonomic nervous system. The longest muscle in the human body is the sartorius. It runs from the waist down across the front of thigh to the knee. Its purpose is to flex the hip and knee. The largest muscle in the body is the gluteus maximus. It moves the thighbone away from the body and straightens out the hip joint.

Extensor muscle: Muscle that contracts and causes a joint to open.

Flexor muscle: Muscle that contracts and causes a joint to close.

Myoneural juncture: Area where a muscle and a nerve connect.

Tendon: Tough, fibrous connective tissue that attaches muscle to bone.

Skeletal System

The skeletal system serves the purpose of support and protection for the body. This system is what allows for the body to stand upright and to move freely. Bones like the Ribs protect the vital organs from physical damage by outside influences.

Skeletal Structure

• The skeletal structure is divided into two groups named the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones which include the head and trunk of the human body. The appendicular skeleton is composed of over 126 bones in the lower region of the body.
• BONES
• CARTILAGE
• TENDONS
• LIGAMENTS

CIRCULATORY SYSYTEM

The circulatory system is made up of the vessels and the muscles that help and control the flow of the blood around the body. This process is called circulation. The main parts of the system are the heart, arteries, capillaries and veins.

- The HeartThe human heart is one of the most fascinating and crucial organs in the human body. The main task that it carries out is the pumping of blood within the body, constantly receiving, purifying, and dishing out blood to various parts of the body.

 -The LungsThere are 2 lungs in the human body, and their task is to supply oxygen to the heart. The intake of air while breathing is carried out by the lungs, and this oxygen is then added into the blood and then transported to the heart. Conversely, impure blood is transported to the lungs via the heart, and this blood is then oxygenated and the remaining components are released back into the air. 

 -Blood and Blood VesselsTechnically speaking these are not organs, but their presence is essential for the respiratory system and the circulatory system of the body. The blood vessels are stretched out to every single part of the body and there are hundreds of thousands of these vessels intertwined in an endless network within the body.

Organs in the Circulatory SystemPrimarily speaking, there are three basic components of the circulatory system. The heart, which serves as a pump; the blood vessels, which carry the blood throughout the body; and lastly, the blood, which is a vital component for the basic functioning of the human body, and which is processed after the intake of oxygen into the human lungs from the atmosphere.

DIGESTIVE SYSTEM

The digestive system breaks down proteins, fats and all carbohydrates (except glucose and fructose which can be absorbed as they are) into smaller molecules which can then be absorbed along with vitamins and minerals.

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html

• MOUTH- The mouth is the beginning of the digestive tract; and, in fact, digestion starts here when taking the first bite of food. Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.
• ESOPHAGUS-Located in your throat near your trachea (windpipe), the esophagus receives food from your mouth when you swallow.
• STOMACH-The stomach is a hollow organ, or "container," that holds food while it is being mixed with enzymes that continue the process of breaking down food into a usable form.
• SMALL INTESTINE-Made up of three segments — the duodenum, jejunum, and ileum — the small intestine is a 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver.
• PANCREAS-The pancreas secretes digestive enzymes into the duodenum, the first segment of the small intestine. These enzymes break down protein, fats, and carbohydrates. The pancreas also makes insulin, secreting it directly into the bloodstream. Insulin is the chief hormone for metabolizing sugar.
• LIVER-The liver has multiple functions, but its main function within the digestive system is to process the nutrients absorbed from the small intestine. Bile from the liver secreted into the small intestine also plays an important role in digesting fat.
• GALLBLADDER-The gallbladder stores and concentrates bile, and then releases it into the duodenum to help absorb and digest fats.
• LARGE INTESTINE-The colon is a 6-foot long muscular tube that connects the small intestine to the rectum. The large intestine is made up of the cecum, the ascending (right) colon, the transverse (across) colon, the descending (left) colon, and the sigmoid colon, which connects to the rectum.
• RECTUM -The rectum (Latin for "straight") is an 8-inch chamber that connects the colon to the anus. It is the rectum's job to receive stool from the colon, to let the person know that there is stool to be evacuated, and to hold the stool until evacuation happens
• ANUS-The anus is the last part of the digestive tract. It is a 2-inch long canal consisting of the pelvic floor muscles and the two anal sphincters (internal and external).

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body.

Structures of the Nervous System

• Central Nervous System (CNS)
  • Brain & Spinal Cord
  • See interneurons
• Peripheral Nervous System (PNS)
  • Contains all nerves outside of the brain & spinal cord.
  • Somatic Nervous System (Voluntary)
    • Two types: Sensory  (or afferent) and motor (or efferent) nerves
  • Autonomic Nervous System (Involuntary)
    • Sympathetic
      • Activated by stress
      • Increase heart rate, breathing rate, pupil size, sweating
    • Parasympathetic
      • Maintains body functions; in control when relaxed.
      • Restores body to pre-stress state

ENDOCRINE SYSTEM:
made up of glands that produce and secrete hormones. These hormones regulate the body's growth, metabolism (the physical and chemical processes of the body), and sexual development and function. The hormones are released into the bloodstream and may affect one or several organs throughout the body.

• The hypothalamus is the master organ, synthesizing and releasing hormones which exert control over the rest of the system. The pituitary gland also exerts some control over the endocrine system.

• The actual endocrine organs include the thyroid gland, the adrenal glands (specifically the adrenal cortex), the pancreas, the ovaries (female), and the testes (male).

• These are the traditional organs of the endocrine system. However, there are other organs that exert effects much like those listed above. The kidneys, for instance, produce erythropoietin, which stimulates the bone marrow to produce more red blood cells. They also release renin, which as an end result, causes the renal tubules to absorb sodium and water.

• The stomach and gastrointestinal systems also have endocrine-like functions - that results in enhanced digestion and absorption of nutrients.

The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction.

The major organs of the external genitalia (penis and vulva) as well as a number of internal organs including the gamete producing gonads (testicles and ovaries). Diseases of the human reproductive system are very common and widespread, particularly communicable sexually transmitted diseases.

Male reproductive system

 

The human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproductive process. The primary direct function of the male reproductive system is to provide the male gamete or spermatozoa for fertilization of the ovum.

Major secondary sexual characteristics includes: larger, more muscular stature, deepened voice, facial and body hair, broad shoulders, and development of an adam's apple. An important sexual hormone of males is androgen, and particularly testosterone.

Female reproductive system

The human female reproductive system is a series of organs primarily located inside of the body and around the pelvic region of a female that contribute towards the reproductive process. The human female reproductive system contains three main parts: the vagina, which acts as the receptacle for the male's sperm, the uterus, which holds the developing fetus, and the ovaries, which produce the female's ova. The breasts are also a reproductive organ during the parenting stage of reproduction. However, in most classifications breasts are not considered to be part of the female reproductive system.
The vagina meets the outside at the vulva, which also includes the labia, clitoris and urethra; during intercourse this area is lubricated by mucus secreted by the Bartholin's glands. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the fallopian tubes. At certain intervals, typically approximately every 28 days, the ovaries release an ovum, which passes through the fallopian tube into the uterus. The lining of the uterus, called the endometrium, and unfertilized ova are shed each cycle through a process known as menstruation. when the reproduction takes place,the sperms of man fertilizes the egg and a new embroyo is formed.

The Human Respiratory System

The Pathway

• Air enters the nostrils
• passes through the nasopharynx,
• the oral pharynx
• through the glottis
• into the trachea
• into the right and left bronchi, which branches and rebranches into
• bronchioles, each of which terminates in a cluster of
• alveoli

Only in the alveoli does actual gas exchange takes place. There are some 300 million alveoli in two adult lungs. These provide a surface area of some 160 m² (almost equal to the singles area of a tennis court and 80 times the area of our skin!).


The purpose of the respiratory system is to bring oxygen into the blood so it can distribute it to the body cells. It also turns oxygen into nutrients and removes carbon dioxide from the body.

1. To supply oxygen to the body.
2. To eliminate carbon dioxide in the body.
3. To regulate the body's pH balance

Excretory system

The excretory system is the system of an organism's body that performs the function of excretion, the bodily process of discharging wastes.

The main purpose of the excretory system is to get rid off the waste materials which can prove harmful to the body if stored.

• The kidneys are the major organs of the excretory system along with the skin and lungs.

Urinary System

	The urinary system includes the kidneys, bladder and tubes. These organs control the amount of water and salts that are absorbed back into the blood and what is taken out as waste. This system also acts as a filtering mechanism for the blood.

(1) Remove wastes from the body.

(2) Regulate levels of electrolytes in the body.

(3) Regulate hydration of the body.

(4) Maintain acid-base balance of the body.

(5) Maintain blood pressure.

IMMUNE SYSTEM
The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances

The immune system, is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.

  

#20 IMCOMPLETE DOMINANCE # 21 DOMAINS OF LIFE

Definition: Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a combined phenotype.

Example:

In cross-pollination experiments between red and white snapdragon plants, the resulting offspring are pink. The dominant allele that produces the red color is not completely expressed over the recessive allele that produces the white color.

#21

 

A phylogenetic tree based on rRNA data, showing the separation of bacteria, archaea, and eukaryotes

When scientists first started to classify life, everything was designated as either an animal or a plant. But as new forms of life were discovered and our knowledge of life on Earth grew, new categories, called "Kingdoms," were added. There eventually came to be five Kingdoms in all - Animalia, Plantae, Fungi, Protista, and Bacteria.

The five Kingdoms were generally grouped into two categories called Eukarya and Prokarya. Eukaryotes represent four of the five Kingdoms (animals, plants, fungi and protists). Eukaryotes are organisms whose cells have a nucleus -- a sort of sack that holds the cell's DNA. Animals, plants, protists and fungi are all eukaryotes because they all have a DNA-holding nuclear membrane within their cells.
The cells of prokaryotes, on the other hand, lack this nuclear membrane. Instead, the DNA is part of a protein-nucleic acid structure called the nucleoid. Bacteria are all prokaryotes.
However, new insight into molecular biology changed this view of life. A type of prokaryotic organism that had long been categorized as bacteria turned out to have DNA that is very different from bacterial DNA. This difference led microbiologist Carl Woese of the University of Illinois to propose reorganizing the Tree of Life into three separate Domains: Eukarya, Eubacteria (true bacteria), and Archaea.
Archaea look like bacteria - that's why they were classified as bacteria in the first place: the unicellular organisms have the same sort of rod, spiral, and marble-like shapes as bacteria. Archaea and bacteria also share certain genes, so they function similarly in some ways. But archaeans also share genes with eukaryotes, as well as having many genes that are completely unique.
Archaea are so named because they are believed to be the least evolved forms of life on Earth ('archae' meaning 'ancient'). The ability of some archaea to live in environmental conditions similar to the early Earth gives an indication of the ancient heritage of the domain.

The early Earth was hot, with a lot of extremely active volcanoes and an atmosphere composed mostly of nitrogen, methane, ammonia, carbon dioxide, and water. There was little if any oxygen in the atmosphere. Archaea and some bacteria evolved in these conditions, and are able to live in similar harsh conditions today. Many scientists now suspect that those two groups diverged from a common ancestor relatively soon after life began.

# 18-Autosomes and Sex chromosomes # 19 Genotype and Phenotype

Autosome-is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females.
Sex chromosomes-are chromosomes involved in a major way in sex determination. No all species use the XY chromosome system that we use. For example, in birds the females are XY and the males are XX!

• The sex chromosomes control what the gender of the offspring will be, where as the autosomes control mostly everything.

SIMILARITIES:

1. both are chormosomes
2. both are inside the nuclus
3. they can be found in any part of the body where cell contains nuclus.

DIFFERENCES:

1. only sex chromosomes( x & y ) are resoponsible for gender of human.
2. sex chromosomal diseases are more severe than automsomal disease( i think)
3. autosomes are 44 in number in a cell whereas gametosomes are only 2.

#19
This is the "outward, physical manifestation" of the organism. These are the physical parts, the sum of the atoms, molecules, macromolecules, cells, structures, metabolism, energy utilization, tissues, organs, reflexes and behaviors; anything that is part of the observable structure, function or behavior of a living organism.
This is the "internally coded, inheritable information" carried by all living organisms. This stored information is used as a "blueprint" or set of instructions for building and maintaining a living creature. These instructions are found within almost all cells (the "internal" part), they are written in a coded language (the genetic code), they are copied at the time of cell division or reproduction and are passed from one generation to the next ("inheritable"). These instructions are intimately involved with all aspects of the life of a cell or an organism. They control everything from the formation of protein macromolecules, to the regulation of metabolism and synthesis.

AS SIMPLE AS:

The codes for the  

The "internally coded, inheritable information", or Genotype, carried by all living organisms, holds the critical instructions that are used and interpreted by the cellular machinary of the cells to produce the "outward, physical manifestation", or Phenotype of the organism.
Thus, all the physical parts, the molecules, macromolecules, cells and other structures, are built and maintained by cells following the instructions give by the genotype. As these physical structures begin to act and interact with one another they can produce larger and more complex phenomena such as metabolism, energy utilization, tissues, organs, reflexes and behaviors; anything that is part of the observable structure, function or behavior of a living organism.

#17 GENES AND ALLELES

A gene is a molecular unit of  heredity in a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA organism chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains. Genes hold the information to build and maintain an organism's cells and pass genetic traits to offspring, although some organelles(e.g. mitochondria) are self-replicating and are not coded for by the organism's DNA. All organisms have many genes corresponding to various different biological traits, some of which are immediately visible, such as eye color or number of limbs, and some of which are not, such asa blood type or increased risk for specific diseases, or the thousands of basic biochemical processes that comprise life.


An allele is one of two or more forms of a gene. Sometimes, different alleles can result in different traits, such as color. Other times, different alleles will have the same result in the expression of a gene.
Most multicellular organisms have two sets of chromosomes, that is, they are diploid. These chromosomes are referred to as homologous chromosomes. Diploid organisms have one copy of each gene (and therefore one allele) on each chromosome. If both alleles are the same, they are homozygotes. If the alleles are different, they are heterozygotes. A population or species of organisms typically includes multiple alleles at each locus among various individuals. Allelic variation at a locus is measurable as the number of alleles present, or the proportion of heterozygotes in the population.

• The word "allele" is a short form of allelomorph ('other form'), which was used in the early days of genetics to describe variant forms of a gene detected as different phenotypes. It derives from the Greek word αλληλος, allelos, meaning "each other".

A gene is a part of the DNA. Alleles on the other hand refer to different versions of the same gene. There are other more subtle differences between the two and this is what we are going to explore on this page:

• Genes are the different parts of the DNA that decide the genetic traits a person is going to have. Alleles are the different sequences on the DNA-they determine a single characteristic in an individual.
• Another important difference between the two is that alleles occur in pairs. They are also differentiated into recessive and dominant categories. Genes do not have any such differentiation.
• An interesting difference between alleles and genes is that alleles produce opposite phenotypes that are contrasting by nature. When the two partners of a gene are homogeneous in nature, they are called homozygous. However, if the pair consists of different alleles, they are called heterozygous. In heterozygous alleles, the dominant allele gains an expression.
• The dominance of a gene is determined by whether the AA and Aa are alike phenotypically. It is easier to find dominants because they express themselves better when they are paired with either allele.
• Alleles are basically different types of the same gene. Let's explain this to you in this way- If your eye color was decided by a single gene, the color blue would be carried by one allele and the color green by another. Fascinating, isn't it?
• All of us inherit a pair of genes from each of our parents. These genes are exactly the same for each other. So what causes the differences between individuals? It is the result of the alleles.
• The difference between the two becomes more pronounced in the case of traits. A trait refers to what you see, so it is the physical expression of the genes themselves. Alleles determine the different versions of the genes that we see. A gene is like a machine that has been put together. However, how it will works will depend on the alleles.

Both alleles and genes play an all important role in the development of living forms. The difference is most colorfully manifest in humans of course! So next time you see the variety of hair color and eye color around you, take a moment and admire the phenomenal power of both the gene and the allele!

#16 Transcription and Translation in Cells

In a prokaryotic cell, transcription and translation are coupled; that is, translation begins while the mRNA is still being synthesized. In a eukaryotic cell, transcription occurs in the nucleus, and translation occurs in the cytoplasm.

Prokaryotic Cell

Because there is no nucleus to separate the processes of transcription and translation, when bacterial genes are transcribed, their transcripts can immediately be translated.

Eukaryotic Cell

Transcription and translation are spatially and temporally separated in eukaryotic cells; that is, transcription occurs in the nucleus to produce a pre-mRNA molecule.

The pre-mRNA is typically processed to produce the mature mRNA, which exits the nucleus and is translated in the cytoplasm.

Eukaryotes

2. Transcription and translation of most eukaryotes are spatially separated.
3. Multiple RNA polyermases.
4. Transcription factor directly binds to the DNA template, but not to the RNA pol.
5. Requires ATP for initiation.
6. Nucleosome / chromatin.

Prokaryotes

1. Polycistronic mRNA.
2.  Coupling transcription and translation.
3. Single RNA polyermase
4. RNA pol holoenzyme itself, by associated sigma factor.
5. No ATP
6. Naked DNA

Most mRNAs are monocistronic(generally one gene for one protein)

I. Eukaryotes vs prokaryotes transcription.

#14 & # 15 Transcription and Translation

#14 Eukaryotic transcription- is more complex than prokaryotic transcription. For instance, in eukaryotes the genetic material (DNA), and therefore transcription, is primarily localized to the nucleus, where it is separated from the cytoplasm (in which translation occurs) by the nuclear membrane. DNA is also present in mitochondria in the cytoplasm and mitochondria utilize a specialized RNA polymerase for transcription. This allows for the temporal regulation of gene expression through the sequestration of the RNA in the nucleus, and allows for selective transport of RNAs to the cytoplasm, where the ribosomes reside.
The basal eukaryotic transcription complex includes the RNA polymerase and additional proteins that are necessary for correct initiation and elongation.

Transcription process:

Eukaryotes have three nuclear RNA polymerases, each with distinct roles and properties:

Name	transcribed
RNA Polymerase I (Pol I, Pol A)	nucleolus	Larger ribosomal RNA (rRNA) (28S, 18S, 5.8S)
RNA Polymerase II (Pol II, Pol B)	nucleus	messenger RNA (mRNA) and most small nuclear RNAs (snRNAs)
RNA Polymerase III (Pol III, Pol C)	nucleus (and possibly the nucleolus-nucleoplasm interface)	transfer RNA (tRNA) and other small RNAs (including the small 5S rRNA)

There are many eukaryotes that differ from the canonical presentation of the roles of RNA polymerasespossess four distinct RNA polymerases. Other organisms utilize RNA polymerase I to transcribe certain protein-coding genes in addition to rRNAs.

Transcription regulation:
The regulation of gene expression is achieved through the interaction of several levels of control including the regulation of transcription initiation. Most (not all) eukaryotes possess robust methods of regulating transcription initiation on a gene-by-gene basis. The transcription of a gene can be regulated by cis-acting elements within the regulatory regions of the DNA, and trans-acting factors that include transcription factors and the basal transcription complex.

#15 TRANSLATION-is the third stage of protein biosynthesis (part of the overall process of gene expression). In translation, messenger RNA (mRNA) produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein. In Bacteria, translation occurs in the cell's cytoplasm, where the large and small subunits of the ribosome are located, and bind to the mRNA. In Eukaryotes, translation occurs across the membrane of the endoplasmic reticulum in a process called vectorial synthesis. The ribosome facilitates decoding by inducing the binding of tRNAs with complementary anticodon sequences to that of the mRNA. The tRNAs carry specific amino acids that are chained together into a polypeptide as the mRNA passes through and is "read" by the ribosome.


             short animation:   http://www.biotopics.co.uk/genes/translation.html

# 12 &13 DNA & RNA

 DNA and RNA are two different nucleic acids found in the cells of every living organism. Both have significant roles to play in cell biology. DNA and RNA structure are similar because they both consist of long chains of nucleotide units. However, there are a few structural details that distinguish them from each other, and if you are to compare DNA and RNA, these would be the results:

(1) RNA is single-stranded while DNA is a double-stranded helix. (2) RNA also has uracil as its base while the DNA base is thymine. However, even with the differences in their structures, DNA and RNA have cooperating roles in the field of Cell Biology.

 DNA contains the genetic information of an organism, and this information dictates how the body’s cells would construct new proteins according to the genetic code of the organism. Within the cell structure, DNA is organized into structures called chromosomes, which are duplicated during cell division.

These chromosomes would then release the genetic codes that will be transcribed and carried by the RNA (specifically the messenger RNA) to the ribosome. The ribosome will then synthesize new proteins that will help the body grow. This is the how the DNA and RNA work together in the body.

#13

• DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken.
• Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized.
• The new strands are assembled from deoxynucleoside triphosphates.
• Each incoming nucleotide is covalently linked to the "free" 3' carbon atom on the pentose (figure) as
• the second and third phosphates are removed together as a molecule of pyrophosphate (PPi).
• The nucleotides are assembled in the order that complements the order of bases on the strand serving as the template.
• Thus each C on the template guides the insertion of a G on the new strand, each G a C, and so on.
• When the process is complete, two DNA molecules have been formed identical to each other and to the parent molecule.

The Enzymes

• A portion of the double helix is unwound by a helicase.
• A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix. In eukaryotes, this molecule is called DNA polymerase delta (δ).
• Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase (epsilon, ε, in eukaryotes) binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides (called Okazaki fragments). Another enzyme, DNA ligase I then stitches these together into the lagging strand.
  

#10 & # 11 COMPARE & COMTRAST MITOSIS & BINARY FISSION &MEISOSIS

#10-Mitosis is the process of forming identical daughter cells by replicating and dividing the original chromosomes, in effect making a cellular xerox. Commonly the two processes of cell division are confused. Mitosis deals only with the segregation of the chromosomes and organelles into daughter cells.
Click here to view an animated GIF of mitosis from http://www.biology.uc.edu/vgenetic/mitosis/mitosis.htm

Prokaryotes are much simpler in their organization than are eukaryotes. There are a great many more organelles in eukaryotes, also more chromosomes. The usual method of prokaryote cell division is termed BINARY FISSION. The prokaryotic chromosome is a single DNA molecule that first replicates, then attaches each copy to a different part of the cell membrane. When the cell begins to pull apart, the replicate and original chromosomes are separated. Following cell splitting there are then two cells of identical genetic composition (except for the rare chance of a spontaneous mutation).

Mitosis is the division of the nucleus into two daughter nuclei. Binary fission is the dividing of a cell into two cells. Either a prokaryotic or eukaryotic cell can do it.


Binary fission is asexual reproduction for prokaryotes whereby a cell duplicates its chromosomes and then splits into two identical cells (each with one copy). Mitosis is essentially the same thing for eukaryotes except that there is an extra step because the nucleus needs to divide too. Mitosis is just the division (essentially, binary fission) of a cell's nucleus
http://www.cellsalive.com/mitosis.htm

#11 AND MEIOSIS

Meiosis produces daughter cells that have one half the number of chromosomes as the parent cell.

2N ® N

Meiosis enables organisms to reproduce sexually. Gametes (sperm and eggs) are haploid.
Meiosis involves two divisions producing a total of four daughter cells.
Click here to go to the chapter on meiosis.

Summary of the Phases of Meiosis

A cell undergoing meiosis will divide two times; the first division is meiosis 1 and the second is meiosis 2. The phases have the same names as those of mitosis. A number indicates the division number (1st or 2nd):

meiosis 1: prophase 1, metaphase 1, anaphase 1, and telophase 1
meiosis 2: prophase 2, metaphase 2, anaphase 2, and telophase 2

In the first meiotic division, the number of cells is doubled but the number of chromosomes is not. This results in 1/2 as many chromosomes per cell.
The second meiotic division is like mitosis; the number of chromosomes does not get reduced.

Both Meiosis and Mitosis are found in complex organisms which reproduce sexually. Mitosis may be used for human growth, the replenishment of depleted organs and tissues, healing, and sustenance of the body. Identical versions of cells can be created to form tissues through Mitosis. Meiosis is a special process reserved for the creation of the egg and sperm cells. The same patterns may be found in many species of plant and animal cell reproduction.

Significance of Mitosis vs. Meiosis

The importance of mitosis is the maintenance of the chromosomal set; each cell formed receives chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell.

Occurrence

Meiosis is found to occur in humans, animals and plants while mitosis is found in single-cell species as well.

Mitosis vs. Meiosis: Process Differences

Mitosis is a method of reproduction for single celled organisms that reproduce asexually. An identical version of the organism is created through splitting of the cell in two. Meiosis may result in millions of spermazoa and egg cells with unique genetic patterns. The mating of the two cells formed by meiosis results in a unique genetic offspring of the same species. Meiosis is a major factor in evolution, natural selection, and biodiversity. The processes of cellular division shown in mitosis and meiosis are present in all manner of life forms including humans, animals, plants, fungi, and single celled organisms and species. Essentially any cell based organism of which all organic life is based will exhibit some form of mitosis and meiosis for growth and reproduction of the individual and species.

#9 Cell Cycle

Mitosis-is the part of the cell cycle when the cell prepares for and completes cell division. During interphase, appropriate cellular components are copied. Interphase is also a time of checkpoints to make sure that the cell is ready to proceed into mitosis. Both of these two phases have further sub-divisions. Since the cell cycle is a "cycle" it has no distinct beginning or ending. Cells are continually entering and exiting the various phases of the cycle.

G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication. Before a cell begins DNA replication, it must ensure that it is biologically ready to take on such a process. G1 is the phase when this cellular monitoring takes place.
During G1, the cell reviews the cellular environment and the cell size to ensure that the conditions are appropriate to support DNA replication. Not until the cell is ready does it leave G1. If all is not ready to undergo DNA replication, cells can pause during G1 and enter a phase called G0. Depending on a cell's preparedness to continue in the cell cycle, G0 can last days, weeks, or even years. When the cell has reached an appropriate size and is in a supportive environment for DNA replication, it will exit either G1 or G0 and enter the next phase of interphase called S phase.

S phase
S phase, or synthesis, is the phase of the cell cycle when DNA packaged into chromosomes is replicated. This event is an essential aspect of the cell cycle because replication allows for each cell created by cell division to have the same genetic make-up. (The specifics of how this replication takes place is covered in the DNA replication SparkNote in the series of SparkNotes dedicated to Molecular Biology.) During S phase a number of events additional to chromosomee replication take place. Cell growth continues through S phase, as does the rate of synthesis of a number of proteins and enzymes that are involved in DNA synthesis. Once DNA replication is complete the cell contains twice its normal number of chromosomes and becomes ready to enter the phase called G2.

G2 phase
Similar to G1, G2 is an intermediate phase, a time for the cell to ensure that it is ready to proceed in the cell cycle. Occurring between the end of DNA replication in S phase and the beginning of cell division in mitosis, G2 can be thought of as a safety gap during which a cell can check to make sure that the entirety of its DNA and other intracellular components have been properly duplicated. In addition to acting as a checkpoint along the cell cycle, G2 also represents the cell's final chance to grow before it is split into two independent cells during mitosis.

Cell Cycle Summary

Interphase is made up of three distinct phases: G1, S phase, and G2. The G1 and G2 phases serve as checkpoints for the cell to make sure that it is ready to proceed in the cell cycle. If it is not, the cell will use this time to make proper adjustments that can include cell growth, correction or completion of DNA synthesis, and duplication of intracellular components. S phase involves the replication of chromosomes. All three stages of interphase involve continued cell growth and an increase in the concentration of proteins found in the cell.