genetic diseases

There are a few genetic diseases that i'm going to talk about in this post. They are: Familial Hypercholesteremia, cystic fibrosis, phenylketonuria, Huntington's disease, Hemophilia, Duchennes muscular dystrophy, progeria, achondroplasia and tay sachs.

Familial Hypercholesteremia (FH) - Familial Hypercholesteremia is charaterized by high cholesterol levels. More specifically high levels of low - density lipoprotein, which is the bad cholestrol. Signs of Familial Hypercholesteremia from high cholesterol usually do not cause any symptoms, but sometimes cholesterol deposits may be visable from the outside, like yellowish patches around the eyelids and lumps in tendons around the hands, feet, elbows and knees. This disorder is autosomal dominant. There are 700 different mutations found in FH patients. Those with FH not only have higher cholesterol but they are also at risk for heart attack and stroke. 600,000 people die each year from Familial Hypercholesteremia. This disease occurs in 1 in every 500 people. Homozygous FH is rare and occurs in 1 in every 1,000,000 people. Homozygous FH caused two inherited genes and the affected person doesn't usually live passed their teens. Treating patients with homozygous FH is very difficult because they are resistant to most cholerestol - lowering drugs. Currently FH is being treated with forms of plasmapheresis which removes low - density lipoprotein from the plasma. The treatments however need to be done every 1 to 3 weeks depending on the state of the patient. Heterozygous HF patients are usually treated with cholesterol lowering drugs, with a low fat and cholesterol diet.

cystic fibrosis (CF) - cystic fibrosis is an inherited disease that affects the lungs and digestive system. 30,000 children and Adults have cystic fibrosis in the United States and 70,000 people worldwide. A mutated gene causes mucus to be producted that gets caught in the lungs and leads to infections. Most people with CF can live to their 30s and 40s with the advanced science we have now. symptoms of CF are: salty tasting skin, persistent coughing, frequent lung infections, weezing and shortness of breath, poor growth and weight gain, and diffeculty in bowel movement. 70% of people with CF are diagnosed by age two, 45% of the people with CF are 18 and older. 1,000 new cases of cystic fibrosis are diagnosed each year. For Cystic Fibrosis there are many therapies and medicines that can be used to help clear the mucus out of the airways. There is the airways clearance techniques (ACT) which helps to clear the mucus from the lungs and helps reduce lung infections. They also do postural drainage and percussion which a person with CF stands, sits and lays in a position that will allow the mucus to break up and their chest and back are pounded to release the mucus. Along with this treatments there are drugs that can be taken to help a person with CF. There are oral antibiotics, which are like tablets and capsules. There are liquid antibiotics and inhaled antibiotics, such as an inhaler or nebulizer. Ibuprofen is common because it's an anti - inflammatory, which helps to slow the rate at which the lungs of a person with CF start to decline. The last thing a person can do, which is the same with most diseases, are nutrition and eating right. Children and teens with CF need extra calories to grow. Having good nutrition and maintaining a healthy body weight can help to reduces other diseases and improve the function of the lungs.

phenylketonuria (PKU) - PKU is a genetic disorder where part of the protein phenylalanine (phe) cannot be produced. phe is in almost all foods, and if phe levels get to high it causes brain damage and severe mental retardation. All babies born in U.S hospitals are tested for PKU. This makes it easier to diagnosis and treat babies earlier. There are usually no symptoms, but there can be some symptoms, including: seizures, musty, mouse-like odor, and in children they tend to have lighter hair and skin. This is an autosomal recessive disorder. The treatment for PKU is a low-protein diet, which includes lots of fruits and vegetables and low protein pastas and breads. They stay on this diet for their whole lives. PKU in infants occurs in 1 in every 10,000 to 15,000 infants.

Huntington's Disease - Huntington's disease is a degeneration of brian cells in certain parts of the brain called the Basal Ganglia, which is responsible for movement and emotions. This causes chorea which is involuntary movements of the body. A person with this disease will have involuntary movements, eventually will not be able to eat, drink or swallow by themselves or walk by themselves. This is a progressive desease, which means a persons condition worsens over time, usually around 10 to 25 years. It could take longer or shorter to progress depending on the person. Huntington's disease can develop at different times of a persons life. Most people though do not show signs of having this disaese until thir middle ages, around 35 - 40 years of age. Though symptoms don't usually appear in a person until their middle ages, a person can develop this disease as an infant or up to age 55. Huntington's disease is and autosomal dominant trait that is passed down from parent to child though a mutated gene. A child of an affected parent has a 50% chance of inheriting the gene. 1 in every 10,000 people or 30,000 Americans have Huntington's disease. 150,000 Americans carry the gene for Huntington's Disease. Currently there is on cure for Huntington's disease. A person can find out if they are at risk for Huntington's disease by a series of lab test and family history test. There are treatments available, but they cannot cure or even slow down the process of the disease, it can only make the person more comfortable. In 2008 a drug called tetrabenazine was the first drug approved to treat Huntington's Chorea. Staying active is the best thing for people with Huntington's. Those who stay active and get exercise typically do better then those who do not.

Hemophilia - Hemophilia is a disorder of the blood - clotting system. Those with hemophilia will bleed for a lot long if they have a cut, then those with normal blood clots. Symptoms of hemophilia is spontaneous bleeding which includes: many large or deep bruises, joint pain and swelling cause by internal bleeding, unexplainded bleeding or bruising, blood in urine or stool, noisebleeds with no obvious cause and tightness in joints. More severe symptoms are: sudden pain, swelling and warmth of large joints, bleeding from injuries, painful, lasting headaches, repeated vomiting, extreme fatigue, neck pain and double vision. There are three types of hemophilia, hemophilia A, hemophilia B, and hemophilia C. Hemophilia A is the most common. Each type of hemophilia is caused by a lack of enough clotting factor, but the clotting factor for each one is different. There is no cure for hemophilia, but most people with hemophilia can lead a fairly normal life. The treatments though are differant depending on the type and severity of the disease. For mild hemophilia A a hormone called desmopressin is injected into a vain to release more clotting factors to stop the bleeding. Moderate to severe hemophilia A or hemophilia B usually involved infusions of clotting factors taken from donated human blood or from recombinant clotting factors, which are genetically engineered. Repeated infusions may be needed if internal bleeding is serious. For hemophilia C plasma infusions are needed.

Duchennes Muscular Dystrophy (DMD) - DMD is a rapid progression of muscular dystrophy that occurs mostly in boys. This is an x-linked recessive disorder. Those with Duchennes Muscular Dystrophy progressively lose function of muscles and have weakness. DMD affects 1 in 3500 male births worldwide. Symptoms of DMD usually occur before the age of 6. The first noticeable symptoms is dely in motor milestones, such as sitting and standing independently. Muscle weakness will occur in the arms and neck, but most severly in the lower part of the body, especially the legs. Most symptoms appear because 1 and 6 years, then there is a steady decline of muscle strength between 6 and 11 years. By age 10 most people require braces for walking and by age 12 they are usually in a wheelchair. muscular weakness often contribute to breathing problems. Cardiomyopathy, which is enlarged heart occurs in early teen in some and after 18 years for the rest. Most people with DMD don't usually live past they're 30s and the most common cause of death is from breathing problems and cardiomyopathy. The treatment of DMD is usually for the symptoms. Prednisone can be taken improve strength and function of those with DMD and has been known to prolong walking for 2 to 5 years. The side effects though include: weight gain, high blood pressure, behavoir changes and delayed growth. Physical therapy is also used to help mobility.

progeria - Hutchinson - Gilford progeria syndrome (progeria or HGPS) is a rare, genetic condition. This is the most common type of progeria. This disorder has an appearance of accelerated aging in children. Children are born healthy and symptoms of HGPS start to appear between 18 and 24 months. Symptoms include: growth failure, loss of body fat and hair, aged - looking skin, stiffness of joins, scalp vains, high-pitched voice, hip dislocation, atherosclerosis (heart disease), cardiovascular disease, and stroke. Children with HGPS die of atherosclerosis at and average of 13 years old. This disease is very rare, there have been only 130 cases of progeria have been documented. progeria isn't passed down in families, it is due to a mutation of the genes. Neither the parents are carriers, the mutation is new. There is no cure of progeria, some children undergo coronary artery bypass to slow the progression of cardiovascular disease. Low dose aspirin taken daily can help to prevent heart attacks and stroke. physical and occupational therapy may help with stiff joints and hip problems to keep the child active. high calorie dietary supplament will give the child extra calories to prevent weight loss.

achondroplasia - achondroplasia is a genetic disorder that results in abnormally short, disporportional limbs. This is also commonly known as dwarfism. The average height of an adult male is 4 feet 4 inches and for an adult female is 4 feet 1 inch. The problem with achondroplasia is the converting of cartilage to bone. The worldwide average for achondroplasia is 1 in every 25,000 births. Achondroplasia is autosomal dominant. Only about 1/8 of cases of achondroplasia are inherited from a parent with achondroplasia, usually the disease is inherited from a new mutation in the DNA. The chance of an affected person passing on the disease to their offspring is 50% per pregnacy. The chance of two affected people passing on the disease is 25% avaraged sized, 50% achondroplasia and 25% chance that the child will have two achondroplasia genes. The danger with a child inheriting two achondroplasia genes is a skeletal disorder which results in early death. achondroplasia cannot be cured and many other things such as hearing loss and dental problems also arise with achondroplasia. Those with the disorder need to be monitored regularly so these things don't happen. Orthopedic proceedure may be done to length bones.

tay sachs disease - Tay sachs is a rare, genetically inherited disorder, where the parent passes it on to their child. This disorder is a deterioration of the brain and nervous system. As it progresses the person loses body function, blindness, deafness, paralysis, and death. Symptoms usually start around 6 months old and the child dies within a few years (on average 4 or 5 years old), but late -onset tay sachs can develop in teens and adults. This disease prevents the body from producing enough hexosaminidase A, which is an enzyme responsible for the break down of fatty substance called GM2 gangliosides. Since the enzyme can't break down the substance it gets stored in the brain. Though this disorder is very rare in the general public this disorder affects mostly those of eastern and central european jewish communities, people from french - canadian communities of Quebec and people from cajun communities of Lousiana. In these communities this disorder can affect up to 1 in 5,000 people. The symptoms of tay-sachs are: seizures, noticeable behavoir changes, increased startle reaction, decreased eye contact, listlessness, slow body growth with increasing head size, delayed mental and social skills. Currently there are no cures for tay sachs, only minor things to make the person more comfortable. Scientist though are working on finding a cure for this disorder.

As you can see from these 9 disorders that, DNA can not only be complicated but the simpliest mutation in the genes can completely change the function of your body.

Works cited

This is a list of websites and sources used to make this blog:









http://ghr.nim.nih.gov/handbook/basics/dna




http://www.en.wikipedia.org/




http://www.dna.gove/




http://blc.arizona.edu/molecular_graphics/DNA-structures/DNA_tutorial.html




http://nobelprize.org/educational/medicine/dna_double_helix/readmore.html




www.slidshare.net/minty/process_of_dna_replication




www.biology.arizona.edu/cell_bio/tutorials/meiosis/




www.phschool.com/science/biology_placemain.html



http://www.cancer.org/

http://www.medicinenet.com/

www.uic.edu/classes/bms/bms655/lesson15.html

http://dwb.unl.edu/teacher/NSF/c10/c10links/www.middlebury.edu/~ch0337/ho/fh.html

www.ccf.org/aboutCF/

http://www.mayoclinic.com/

http://www.genome.gov/

http://www.learn.genetics.utah.edu/

cancer myths and truths

On the news all the time you here that this can give you cancer or that can give you cancer, but can they really? Here are a list of cancers myths and why they are myths.



1. cell phones cause cancer: cell phones do emit radio waves, but these radio waves are like the radio waves emitted by a television. Cell phones do not cause brain tumors.



2. One of the most popular myths about cancer among woman is that antipersiprants and deoderants cause breast cancer. There is not evidance from recent studies can conclude that wearing them causes breast cancer.



3. cancer causes hairloss. Cancer its self does not cause hairloss, but effects from cancer treatment can cause hairloss.



4. certain types of cancers are contagious. This is not true, you cannot develop cancer from another person. Though some disease such as HIV are contagious and can lead to some types of cancer.



5. If a parent has cancer, they will pass it on to their offspring. This is totally NOT true. Cancer is caused by mutations in the genes, like was dicussed previously. Cancer is usually not hereditary.



6. Only women get breast cancer. This is a common myth that is not true. 1500 men are diagnosed with breast cancer every year and every year 500 of those men die from breast cancer. Breast cancer in men is not as common as in women, but they can still develop breast cancer.



7. hair dye causes cancer. There is no evidance to prove that using hair dye causes cancer.



8. drinking water with flouride in it causes cancer. Half of Americans drink water with flouride in it, there are no creditable evidance that drinking water with flouride causes cancer.



9. coral calcium can cure cancer. coral calcium is a dietary supplement made from marine coral. This is not true, coral calcium cannot cure cancer and legal action has been taking against those saying it can.



Here are some truths about cancer:



1. eating grilled meats cause cancer. grilling meat causes a chemical called heterocyclicamines, to be created, this can be harmful. This chemical is found in higher qualities when meat is well done or burnt. It is recommended that you limit grilled meat and avoid eating the burnt parts



2. magnetic field exposure causes cancer. Some say that being around powerlines causes cancer. While many test have proved this to be inconclusive, still the National Institute of Environmental Health Sciences suggests distancing yourself from these kinds of things.

causes of cancer

around 500,000 people die each year from cancer. Cancer is currently the 2 largest cause of death behind cardiovascular disease. The risk of developing cancer is 50% or every one and two people. some of the risks of cancer are: growing older, tobacco, sunlight, ionizing radiation, certian chemicals, some viruses or bacteria, certian hormones, family history, alcohol, poor diet, lack of physical activity and being overweight. Most of these risk factors can be avoided.



growing older - we cannot avoid growing older, but most of the diagnosis of cancer are those who are over the age of 65, though children and those younger the 65 develop cancer.



tobacco - tobacco use is avoidable, every year around 180,000 people die from cancer related to tobacco use. Just being around tobacco smoke, such as secondhand smoke increases the risk. Those who smoke are at a higher risk of cancer of the: lung, larynx, mouth, kidney, throat, stomach and cervix. Those who use smokeless tobacco are at a higher risk of developing cancer of the mouth.



sunlight - sunlight from uv rays also increases the risks of cancer. uv rays come from sun, sunlamps and tanning booths. This can cause skin cancer. Though we cannot completely avoid uv rays, unless we never go outside, but we can help lower our risk by using sunscreen and wearing a hat.



ionizing radiation - ionizing radiation comes from radon gas and more commonly x-rays. The x-rays that the doctor gives you, produce only a small amount of ionizing radiation, which is not enough for a person to develop cancer.



some viruses and bacteria - the human papillomavirus (hpv) increase the risk of developing cervical cancer, hepatitis B and C viruses increase the risk of liver cancer, Human Immunodeficiency virus (HIV) are at a greater risk for lymphoma and a rare cancer called kaposi's sacroma and those with the epstein - barr virus are at greater risk for kaposi's sacroma.



Family history of cancer - Most cancers occur because of mutations in genes that happen over time and are passed on. Cancer to run in a family is usual, though some times such as: breast cancer, ovary, prostate and colon cancers sometimes run in families. Usually several cases of the same cancer in the same family is just a matter of chance. Just because your family has a history of a certian cancer, does not mean that you will develop the cancer.



Alcohol - having more then two drinks a day may increase the risk of developing cancers of the: mouth, throat, larynx, liver and breast. Risks are higher with those who both drink alcohol and use tobacco.



poor diet, lack of physical activity and being overweight - those who eat diet that is high in fat have increased risk for cancers of the colon, uterus and prostate. Those who do not get regular physical activity and/or are overweight have an increase risk for cancers of the breast, colon, kidneys and uterus. Risks can be decreased by eating a healthy diet that includes foods that are high in fiber, vitamins and minerals but eating whole-grain breads and cereals, eating enough fruits and vegatables everyday and limiting the amout of high fat foods (butter, whole milk, fried foods etc.). Also getting a moderate amount of physical activity for 30 minutes 5 times a week, will help to reduce body weight and keep you healthier.



As you see most of these risk factors can be avoided. Avoiding these things, or if you can't avoided them reducing your exposure to them will decrease your risks of developing cancer now or in the future.

Stem cells

Stem cells are unspecialized cells in the body. Stem cells are resently being concidered as a way to cure many diseases like: Huntington's disease, diabetes, and muscular dystrophy. Stem cells can be taking from embryos, adults, imblicial cord and blood. The most common though are embryonic stem cells and adult stem cells.

Currently embryonic stem cells are being called the most effective, but it poses many ethical concerns. The pros of embryonic stem cells are that all the embryos left over and not being used can be used to help people with these currently uncurable diseases. The cons of embryonic stem cells are that it kills the embryo, dying it the right to become a person like you and me. But this is hard to decide, since some people can't decide when an embryo is actually living. Some people call it murder others, simply don't see a problem with it because they do not believe that the embryo is living yet.

Everyones opinion is different. Though many people believe that embryonic stem cell research is wrong, there has been many successful trials of using stem cells. One example are the researchers from univeristy of texas medical branch at Galveston. They have used embryonic stem cells to help repair lungs in rats. It has been successful, but it has not been used in humans yet. using embryonic stem cells could help cure those with severe lung disorders such as cystic fibrosis or cronic obstructive pulomary disease.

But for those who are against embryonic stem cell research, but still want to help cure those diseases, there is a second option. Adult stem cell research, these are stem cells taken from an adult. These is less controversal because using adult stem cells do not kill the adult. Adult stem cells seem to be a little harder to get though, but here also have been success using them. Adult stem cells have been able to be used to help cure some cancers, such as brain tumors, ovarian cancer, and leukemia. They have also been used to help cure immune diseases, stroke, anemia and heart disease.

Now that we know that both embryonic stem cells and adult stem cells are both effective at curing diseases, all there is to think about is whether we believe in using embryonic stem cells or not. Maybe researchers can find was to make stem cells from the imbilical cord or blood to work, or maybe they can find new sources of stem cells. Ether way we already have too successful ways of doing this.

inheritance and pedigree analysis

Many diseases such as cancer, huntington's disease, diabetes, cystic fibrosis and tay sachs are all hereditary. Though each one can be inherited differently. Pedigree charts are often used to show the inheritance of something between family members and can also be used to figure out which time of inheritance it is. The different types of inheritance I will be discussing are x-linked dominant, x-linked recessive, y-linked, autosomal dominant and autosomal recessive.

x-linked dominant - x-linked dominant disorders are disorders located on the x chromosome. There are few disorders that inherit x-linked dominant inheritance. Examples include: Rett syndrome, Aicardi syndome, and Klinefelter symdrome. With x - linked dominant, the disorder is never passed from father to son. All daughters of an affected father and a normal mother will be affected, while all sons will be normal. 1/2 of the sons and 1/2 of the daughters of an affected mother and normal father will be affected as well. Females are more likely to be affected then males and most x-linked disorders are lethal in males.

x-linked recessive- x-linked recessive disorders are also located on the x chromosome, and are more common then x-linked dominant. Examples of x-linked recessive disorders are: Hemophilia A, Duchenne Muscular Dystrophy, Lesch - Nyhan syndrome, male pattern baldness, color blindness and Turner syndrome. The x-linked recessive is also never passed from father to son. Males are much more likely to be affected then females are. All affected males are affected because of their mother. It is usually passed from the affected to grandfather to his carrier daughters, which affect half of the grandsons.

y - linked - Y-linked disorders are located on the y chromosome and are very few. The most common one is male infertility. Since only males inherit a y chromosome, all of the sons of an affect male will also be affected while none of the daughters will be.

autosomal dominant - autosomal disorders mean that only one mutated copy of a gene is required for a person to be affected by an autosomal dominant disorder. Each affected person had a least one affected parent, and there's a 50% chance of a children of an affected parent will get the disorder. Some examples of autosmal dominant Huntington's disease, Marfan syndrome and Familial hypercholesterolemia. Autosomal dominant disorders do not skip generations. Males and females both have equal likelihood of inheriting the disorder.

Autosomal recessive - Autosomal recessive disorders are like autosomal dominant disorders, but two copies need to be inherited instead of one. Some examples of autosomal recessive disorders are: cystic fibrosis, sickle-cell disease, tay-sachs disease and roberts syndrome. In autosomal recessive disorders males and femals are equally likely to inherit the disorder. Disorders often skip generations, and affected children can be born to unaffected parents.

genetics and inheritance

Remember back to meiosis. During meioses half of your chromosomes are passed to you through you mother and the other half from your father. In 1866 an Austrian monk, named Gregor Mendel worked on the inheritance of genetics by breeding peas together.

Above is his experiment. Mendel started by crossing a round yellow pea plant (YY) and a wrinkly green pea plant (yy). All of the first generation ended offspring ended up being round and yellow. Mendel then took the first generation offspring and crossed them. What Mendel found was that most of the second generation plants were yellow and around, but a few where wrinkly and green. Mendel continued to do this until he noticed that there was always a 3:1 ration of yellow to green and round to wrinkly.

From this experience Mendel not only was able to better understand inheritance but he was also able to figure out about Dominant and recessive genes. the yellow round plants were Dominant while the wrinkly green plants where recessive. the first generation offsprings had an equal chance to receive either the dominant or recessive trait. One parent passed on the dominant trait while the other passed on the recessive trait, but since one trait was dominant it was the only trait shown.

An organism with two dominant traits are called homozygous dominant, (homo means same). An organism with two recessive traits are known as homozygous recessive and an organism with one dominant trait and one recessive trait are known as heterozygous (heter means different).

In some cases though, both traits can be shown, or neither trait could be shown. This is known at incomplete dominance or co - dominance.

Incomplete dominance - incomplete dominance is when two organism like flowers are crossed (breed) and the offspring ends up having a mixture of both of the parents traits. The picture to the left starts with a homozygous recessive white flower crossed with a homozygous dominant red flower. The first generation ends up all being heterozygous pink flowers. When the two heterozygous pink flowers are crossed the result is a 1:2:1 ratio. 1 homozygous recessive, 2 heterozygous and 1 homozygous dominant traits are inherited by the second generation offspring.

Co-Dominance - results when neither of the traits completely dominants the other trait. So instead of having a dominant and a recessive trait, both traits are equally dominant. The picture the the right is the result of a white flower crossed with a red flower. All of the first generation flowers result in patches of red and white.

How do you know which traits are dominant? Here is a list of dominant vs. recessive traits. Compare your traits with you parent's traits and you can find out which parent you inherited which trait from.

Dominant Recessive

Brown eyes any other color eyes

curly hair staight hair

widows peak normal hairline

dimples & freckles no dimples & freckles

double jointed normal joints

These are just a few, there are many more, but this it just to give you an idea.

Genes, proteins and traits

We each have our own genes, that's genes, not jeans. Genes are part of out DNA that contains codes for certain proteins. Proteins are large molecules responsible for the structure, function and regulation of your body. Proteins are made of amino acids, there are 20 different amino acids which can combine and form many proteins. These Proteins make up every single persons traits.

However nothing is life is prefect, neither is protein formation. Our traits are based on the proteins made, but the proteins are based on the order of the codons ( these are just a three letter code). In some cases the order of the codons can get mutated, resulting in a mutation of the protein. This is known as as point mutations. The point mutations are either a frameshift mutation, stop codon, missense mutation, or a mRNA splicing mutation.

Frameshift mutation - A frameshift is when the the codon sequence starts at the wrong place, leading to a different amino acid sequence, which makes different proteins.

Missense mutation - Happens when a different nucleotide replaces the orginal nucleotide, causing an incorrect amino acid, which could cause a mutation in the protein.

mRNA splicing mutation - is when a part of the code is left out, resulting in a shortened portein.

These proteins make up our traits, each person had different traits because of the proteins made and because of inheritance, which will be covered later.

Meiosis

Meiosis is cell division, which is how genes are inherited from parent to offspring, through sexual reproduction. Every Person has 46 chromosomes in their body. Half of your chromosomes come from your mother and half from you father. These are found in the gamates, which means they are in either the egg of a female or the sperm of a male. When the egg is fertilized, it becomes diploid, meaning is has two sets of chromosomes. Meiosis goes through two processes, each containing different phases. In meiosis I the parent cell divides to two identical daughter cells. In meiosis I there are 4 phases: prophase, metaphase, anaphase and telophase.
Prophase I: the Chrosomes are duplicated during interphase I, before Prophase I. During prophase the duplicated homologous ( same) pairs of chromosomes go through crossing - over. This is just when the chromosome pairs, also known as sister chromatids, cross - over each other and exchange parts of the chromosome parts. This allows for varieties in genes. Prophase takes the longest time out of all of the other phases. Also during prophase the nucleolus disappears and the meiotic spindles start to form on opposite poles of the cell.
Metaphase I: During Metaphase I the homologous pairs of chromosome line up on the metaphase plate, in random orders. The the spindle fibers come down from the poles and attach to the homologous chromosomes.
Anaphase I: In anaphase I the spindle fibers pull the chromosomes to opposite sides of the cell. the tetrads stay connected at the centromere. They are not yet seperated, this takes place during anaphase II.
Telophase I: During Telophase I the chromosome pairs are on two different sides of the cell, which makes two daughter cells that are each haploid ( 23 chromosomes ) and each contain two sets of chromatids. the spindle disappears and cytokinesis starts. In cytokinesis a cleavage furrow forms, which makes the cells into two seperate cells. . This concludes meiosis I and meiosis II proceeds, starting with Prophase II.


Meiosis II: Meiosis II takes the two daughter cells and divides them into four daughter cells. This process starts with Prophase II.

Prophase II: The centrioles duplicate. No new chromosomes are replicated during meiosis II. the nuclear envelope disappairs and the spindles form.

Metaphase II: single chomosomes form along the metaphase plate. the kinetochore of the sister chromatids are connected to the kinetochore microtubles coming from the poles.

Anaphase II: the centromeres split and the to sister chromatids move to opposite sides of the poles, these are now seperate chromosomes.

Telophase II: cytokinesis forms four daughter haploid cells which because of crossing over results in recombination of the parents chromosomes. This then concludes the meiosis process.

DNA Replication

DNA can replicate to make identical copies of the DNA strands. DNA replication starts with the double helix during the initiation stage when Helicase (an enzyme) is used to "unzip" the DNA. In other words Helicase seperates the two double stranded DNA to seperate strands of DNA, one being the lagging strand and the other the leading strand.

The next step in DNA replication is Elongation , this starts at the replication fork. RNA primase starts this process by adding RNA primers to the DNA strands. the primers are like a green light for the replication to start. DNA replication cannot start though, until RNA primase has added a primer. DNA polymerase starts to add DNA nucleotides from the 3' to 5' ends of the DNA. Since the nucleotides can only be added from the 3' to 5' end, the lagging strand is discontinual. polyermase will add a fragment of DNA nucleotides known as Okazaki fragments (shown in picture above). Polymerase will make a bunch of these Okazaki fragments on the lagging strand. The leading strand on the other hand is a continous replication. The leading strand is already in the 3' to 5', so DNA polymerase can start from the primers and continue without stoping or making Okazaki fragments.

The last step of DNA replication is Termination. Termination occurs when DNA polymerase reaches the end of the strands. the RNA primers are removed and ligase comes and connects the Okazaki fragments together on the lagging strand. This completes the replication of DNA.

DNA Structure

Adenine and Guanine are purines. Cytosine and Thymine are pyrimidines. Purines are larger. A purine and a pyrimidine must pair together, so that the DNA is a certian width. If two pyrimidines were paired together, the DNA would be too narrow, if two purines were paired together the DNA would be too wide. This is way Adenine pairs with Thymine and Guanine pairs with Cytosine.

DNA is constructed by a phosphate backbone, which are held together by phosodiester bonds. DNA starts with a phosphate attached to a deoxyribose sugar, which is attached to one for the four base pairs. DNA is double stranded, which forms a twist of the strands, which is called a double helix.

Rosalind Franklin took the first x-ray of DNA, this x-ray is known as photo 51. From this photo Watson and Crick were able to make the first model of DNA as a double helix. From the photo they were also able to tell how far apart the nucleotides are from eachother. They figured out that DNA makes one complete twist every 10 nucleotides. There are also .34 nm between each base pair and 3.4 nm is one full twist. DNA is also antiparell, which runs 3' to 5'. Watson and Crick later received a noble prize for their work with DNA structure. Rosalind Franklind died before she was recognized and never received a noble prize.

What is DNA?

DNA is short for Deoxyribonucleic acid. Every person has DNA inside of almost all of the cells in their body. It is the building block for each persons genetic makeup. No two people have the same DNA, and is inherited from parent to offspring (will be covered later). Most DNA is located in the the cell nucleus and some is located in the mitochondria. DNA is made up of four base pairs, A (Adenine), G (Guanine), T (Thymine) and C (Cytosine). In DNA Adenine always pairs with Thymine and Cytosine always pairs with Guanine. DNA has a specific structure and can be replicated ( will be discussed later). DNA is often compared to a blueprint that construction workers use before the actual construction of a building, because it contains the information needed for the entire body.