Human Physiology/Genetics and inheritance - Wikibooks, open books for an open world
4 Inherited Genetic Disease Genetic inheritance begins at the time of conception. . Good examples are just as important as good genes. . first discovered in and most patients have Celtic ancestry dating back 60 or 70 generations. And even the best clinical genetic test, carried out in a medical lab For example , cystic fibrosis is linked to one particular gene, but you have to inherit the But figuring out your expiration date is more complex than just. peers, according to one of the largest studies to date into genetic diversity. However, the study found no link between genetic diversity and high blood would believe a diverse gene-pool is a good thing, but the discovery that for instances of when people had inherited identical copies of genes from.
The kids inherit both sets of genes, which can combine with blond genes from their mates to produce fair-haired offspring. But don't blame the mailman if your child's hair is surprisingly red -- the interplay of genes can create all sorts of unexpected traits.
And if your son eventually loses his hair, he can point a finger at either parent: Contrary to popular belief, the dominant gene for male-pattern baldness can be passed down by moms or dads. Joseph Chisolm, of Secaucus, New Jersey, certainly knows how arbitrary inheritance can be.
He's black and his wife, Donelle, is white, so they weren't surprised that their first child, 4-year-old Jaydon, was dark-skinned and brown-eyed. But their 1-year-old son, Jordon, is startlingly different: One study found that families tend to have similar facial expressions when they're happy, sad, angry, disgusted, surprised, or thinking hard.
And kids don't just pick up these reactions from watching us: Blind members of 21 families in the study also grimaced, smiled, and scowled like their relatives 80 percent of the time. Other likenesses are quirkier. Both Kim Whorton, of Birmingham, Alabama, and her daughter Zoe, the oldest of 3-year-old triplets, have dimples in their shoulder blades -- a rare trait that's been traced to an abnormality on a specific chromosome.
In some cases, one genetic trait may be linked to others. Check the hair whorl at the top of your child's head: If it swirls counterclockwise, he has a chance of being left-handed or ambidextrous, which suggests that both hair pattern and handedness are driven by some of the same genes. Personality Plus Scientists have little doubt that genes can affect a child's behavior, but exactly how nature and nurture work together is still somewhat of a mystery.
One recent study concluded that almost all psychological traits are at least somewhat genetic. Research has also shown that twins often have similar personalities even when they have been raised apart. The resemblances can be uncanny. Amber Carlsen, of Salt Lake City, says her 2-year-old daughter, Haylee, is a deja vu version of herself as a child -- bossy, independent, and fastidious.
Carey, "but genetics can certainly shape preferences for things like color, which could lead a child to make choices that are similar to a parent's.
One recent study found that kids who have a taste gene that's associated with a sensitivity to bitterness are less likely to pick milk or water as their favorite drink and more likely to love sugary soft drinks and cereals.
The Environment However, there's almost always a connection between genetics and environment. Musical talent is a classic example. People who have perfect pitch are four times more likely than those with only average singing voices to say that a relative has this natural gift. Yet research has also found that most people with perfect pitch started taking music lessons before age 6, and that only 3 percent of people who started voice lessons after age 9 have perfect pitch -- suggesting that both genetics and training affect one's singing voice.
Average IQ scores have gone up in the past 50 years thanks to changes such as better early-childhood education, experts say, not because we're innately smarter.
It's all in your genes: how DNA explains your sense of humour, sleep patterns, and phobias
And intelligence may run in families partly because bright parents tend to provide a richer learning environment -- by having more books, for example. In fact, two recent studies found that the IQ of firstborn children is slightly higher than that of their younger siblings -- possibly because they received more undivided attention.
Watson and Francis Crickwith help from Rosalind Franklin Jo Hin Tjio and Albert Levan established the correct chromosome number in humans to be 46 The Meselson-Stahl experiment demonstrates that DNA is semi-conservatively replicated The genetic code is arranged in triplets Howard Temin showed using RNA viruses that Watson's central dogma is not always true Restriction enzymes were discovered in studies of a bacterium Haemophilus influenzae, enabling scientists to cut and paste DNA DNA is sequenced for the first time by Fred Sangr, Walter Gilbertand Allan Maxam working independently.
It encodes the CFTR protein. Defect in this gene causes Cystic Fibrosis The genome of Haemophilus influenza is the first genome of a free living organism to be sequenced. In response to an enzyme RNA polymerase breaks the hydrogen bonds of the gene. A gene is a segment of DNA which contains the information for making a protein. As it breaks the hydrogen bonds it begins to move down the gene.
Next the RNA polymerase will line up the nucleotides so they are complementary. Some types of RNA will leave the nucleus and perform a specific function. Translation is the synthesis of the protein on the ribosome as the mRNA moves across the ribosome. There are eleven basic steps to translation.
The mRNA base sequence determines the order of assembling of the amino acids to form specific proteins. Transcription occurs in the nucleus, and once you have completed transcription the mRNA will leave the nuecleus, and go into the cytoplasm where the mRNA will bind to a free floating ribosome, where it will attach to a small ribosomal subunit.
The complex then binds to a large ribosomal subunit. Methionine-tRNA is bound to the P site of the ribosome.
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Another tRNA containing a second amino acid lysine binds to the second amino acid. Binding to the second condon of mRNA on the A-site of the ribosome.
Peptidyl transferase, forms a peptide3 bond between the two amino acids methionine and lysine. Another tRNA with attached amino acid glutamine moves into the A site and binds to that codon. It will now form a peptide bond with lysine and glutamine. Then this codon will tell it to release the polypeptide chain. These are some good sites to visit B http: If you want to hear the descriptions in this process go to B web site and select the Inner Life: Inheritance[ edit ] Children inherit traits, disorders, and characteristics from their parents.
Children tend to resemble their parents especially in physical appearance. However they may also have the same mannerisms, personality, and a lot of the time the same mental abilities or disabilities. Many negatives and positives tend to "run in the family". A lot of the time people will use the excuse "It runs in the family" for things that have alternative reasons, such as a whole family may be overweight, yes it may "run in the family" but it could also be because of all the hamburgers and extra mayo that they all eat.
Or the fact that after they eat the hamburgers they all sit on the couch and don't move for the rest of the evening. Children may have the same habits good or bad as their parents, like biting their nails or enjoying reading books. These things aren't inherited they are happening because children imitate their parents, they want to be like mom or dad.
Good examples are just as important as good genes. Inheritance pattern Examples Autosomal dominant Only one mutated copy of the gene is needed for a person to be affected by an autosomal dominant disorder.
Each affected person usually has one affected parent. Many disease conditions that are autosomal dominant have low penetrance, which means that although only one mutated copy is needed, a relatively small proportion of those who inherit that mutation go on to develop the disease, often later in life.
Huntingtons disease, Neurofibromatosis 1, HBOC syndrome, Hereditary nonpolyposis colorectal cancer Autosomal recessive Two copies of the gene must be mutated for a person to be affected by an autosomal recessive disorder. An affected person usually has unaffected parents who each carry a single copy of the mutated gene and are referred to as carriers. Cystic fibrosis, Sickle cell anemia, Tay-Sachs disease, Spinal muscular atrophy, Muscular dystrophy X-linked dominant X-linked dominant disorders are caused by mutations in genes on the X chromosome.
Only a few disorders have this inheritance pattern. Females are more frequently affected than males, and the chance of passing on an X-linked dominant disorder differs between men and women. The sons of a man with an X-linked dominant disorder will not be affected, and his daughters will all inherit the condition.
Some X-linked dominant conditions, such as Aicardi Syndrome, are fatal to boys, therefore only girls have them and boys with Klinefelter Syndrome. Hypophosphatemia, Aicardi Syndrome X-linked recessive X-linked recessive disorders are also caused by mutations in genes on the X chromosome. Males are more frequently affected than females, and the chance of passing on the disorder differs between men and women. The sons of a man with an X-linked recessive disorder will not be affected, and his daughters will carry one copy of the mutated gene.
Only males can get them, and all of the sons of an affected father are affected. Since the Y chromosome is very small, Y-linked disorders only cause infertility, and may be circumvented with the help of some fertility treatments. Male Infertility Mitochondrial This type of inheritance, also known as maternal inheritance, applies to genes in mitochondrial DNA. Because only egg cells contribute mitochondria to the developing embryo, only females can pass on mitochondrial conditions to their children.
Leber's Hereditary Optic Neuropathy LHON Mechanisms of inheritance[ edit ] A person's cells hold the exact genes that originated from the sperm and egg of his parents at the time of conception. The genes of a cell are formed into long strands of DNA. Most of the genes that control characteristic are in pairs, one gene from mom and one gene from dad. Everybody has 22 pairs of chromosomes autosomes and two more genes called sex-linked chromosomes. Inherited traits and disorders can be divided into three categories: Unifactorial Inheritance[ edit ] Chart showing the possibilities of contracting a recessive defect, from two carrier parents.
Traits such as blood type, eye color, hair color, and taste are each thought to be controlled by a single pair of genes. The Austrian monk Gregor Mendel was the first to discover this phenomenon, and it is now referred to as the laws of Mendelian inheritance. The genes deciding a single trait may have several forms alleles. For example, the gene responsible for hair color has two main alleles: The genetic codes for red and brown can be either dominant or recessive.
In any case, the dominant gene overrides the recessive. When two people create a child, they each supply their own set of genes. Similar rules apply to different traits and characteristics, though they are usually far more complex. Multifactorial inheritance[ edit ] Some traits are found to be determined by genes and environmental effects. Height for example seems to be controlled by multiple genes, some are "tall" genes and some are "short" genes.
A child may inherit all the "tall" genes from both parents and will end up taller than both parents. Or the child my inherit all the "short" genes and be the shortest in the family.
More often than not the child inherits both "tall" and "short" genes and ends up about the same height as the rest of the family. Good diet and exercise can help a person with "short" genes end up attaining an average height. Babies born with drug addiction or alcohol addiction are a sad example of environmental inheritance. When mom is doing drugs or drinking, everything that she takes the baby takes.
These babies often have developmental problems and learning disabilities. A baby born with Fetal alcohol syndrome is usually abnormally short, has small eyes and a small jaw, may have heart defects, a cleft lip and palate, may suck poorly, sleep poorly, and be irritable. About one fifth of the babies born with fetal alcohol syndrome die within the first weeks of life, those that live are often mentally and physically handicapped.
Sex-linked Inheritance[ edit ] Sex-linked inheritance is quite obvious, it determines your gender. Male gender is caused by the Y chromosome which is only found in males and is inherited from their fathers. The genes on the Y chromosomes direct the development of the male sex organs. The x chromosome is not as closely related to the female sex because it is contained in both males and females.
Males have a single X and females have double XX. The X chromosome is to regulate regular development and it seems that the Y is added just for the male genitalia.
When there is a default with the X chromosomes in males it is almost always persistent because there is not the extra X chromosome that females have to counteract the problem. Certain traits like colorblindness and hemophilia are on alleles carried on the X chromosome. For example if a woman is colorblind all of her sons will be colorblind. Whereas all of her daughters will be carriers for colorblindness.
Exceptions to simple inheritance[ edit ] Our knowledge of the mechanisms of genetic inheritance has grown a lot since Mendel's time. It is now understood, that if you inherit one allele, it can sometimes increase the chance of inheriting another and can affect when or how a trait is expressed in an individuals phenotype.
There are levels of dominance and recessiveness with some traits. Mendel's simple rules of inheritance does not always apply in these exceptions. Polygenic Traits[ edit ] Polygenic traits are traits determined by the combined effect of more than one pair of genes.
Human stature is an example of this trait. The size of all body parts from head to foot combined determines height. The size of each individual body part are determined by numerous genes. Human skin, eyes, and hair are also polygenic genes because they are determined by more than one allele at a different location.
Intermediate Expressions[ edit ] When there is incomplete dominance, blending can occur resulting in heterozygous individuals.
An example of intermediate expression is the pitch of a human male voice. Homozygous men have the lowest and highest voice for this trait AA and aa. The child killer Tay- Sachs is also characterized by incomplete dominance.
Co-dominance[ edit ] For some traits, two alleles can be co-dominant. Were both alleles are expressed in heterozygous individuals. An example of that would be a person with AB blood. These people have the characteristics of both A and B blood types when tested. Multiple-Allele Series[ edit ] There are some traits that are controlled by far more alleles.
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For example, the human HLA system, which is responsible for accepting or rejecting foreign tissue in our bodies, can have as many as 30, different genotypes! The HLA system is what causes the rejection of organ transplants. The multiple allele series is very common, as geneticists learn more about genetics, they realize that it is more common than the simple two allele ones.
Modifying and Regulator Genes[ edit ] Modifying and regulator genes are the two classes of genes that may have an effect on how the other genes function. Modifying Genes alter how other genes are expressed in the phenotype. For example, a dominant cataracts gene may impair vision at various degrees, depending on the presence of a specific allele for a companion modifying gene.
However, cataracts can also come from excessive exposure to ultraviolet rays and diabetes. Regulator Genes also known as homoerotic genes, can either initiate or block the expression of other genes. They also control a variety of chemicals in plants and animals. For example, Regulator genes control the time of production of certain proteins that will be new structural parts of our bodies.
Regulator genes also work as a master switch starting the development of our body parts right after conception and are also responsible for the changes in our bodies as we get older. They control the aging processes and maturation. Incomplete penetrates[ edit ] Some genes are incomplete penetrate.
Which means, unless some environmental factors are present, the effect does not occur. For example, you can inherit the gene for diabetes, but never get the disease, unless you were greatly stressed, extremely overweight, or didn't get enough sleep at night. Inherited Genetic Disease[ edit ] Some of the most common inherited diseases are hemochromatosis, cystic fibrosis, sickle cell anemia and hemophilia. They are all passed along from the parents and even if the parents don't show signs of the disease they may be carriers which mean that all of the children they have may be born with the disease.
There is genetic testing that may be done prenatally to determine if the baby is conflicted with one of these diseases. Haemochromatosis types are inherited in an autosomal recessive fashion. Haemochromatosis type 4 is inherited in an autosomal dominant fashion.
Even though most people have never heard of hemochromatosis it is the most common inherited disease. About 1 in are born with hemochromatis and 1 in 9 are carriers. The main characteristic is the intake of too much iron into the inflicted body.
Iron is crucial to the workings of hemoglobin but too much iron is just as bad as too little iron. With hemochromatosis deposits of iron form on almost every major organ especially the liver, heart and pancreas, which causes complete organ failure. Hemochromatosis patients usually absorb two or three times the iron that is needed for normal people. Hemochromatosis was first discovered in and most patients have Celtic ancestry dating back 60 or 70 generations.
Treatments for hemochromatosis[ edit ] The most common treatment for hemochromatosis is to induce anemia and maintain it until the iron storage is reduced. This is done by therapeutic phlebotomy. Phlebotomy is the removal of a unit of blood about mls.
This must be done one to two times a week and can take weeks, months, or years to complete. After this treatment some patients will never have to do it again and others will have to do it many times over the course of their life.
Patients who undergo their recommended treatments usually go on to live a long and healthy life.
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Patients who decide against treatment increase their chances of problems such as organ failure -- or even death.
Along with phlebotomy treatment, patients should stick to a low iron diet and should not cook with iron cookware. Cystic Fibrosis CF [ edit ] Cystic fibrosis is a disease that causes thick, sticky mucus to build up in the lungs and digestive tract.
It is the most common lung disease in children and young adults and may cause early death. The mucus builds up in the breathing passages of the lungs and in the pancreas. The build up of the mucus results in terrible lung infections and digestion problems. Cystic fibrosis may also cause problem with the sweat gland and a man's reproductive system. There are more than 1, mutations of the CF gene, symptoms vary from person to person. The most common symptoms are: No bowel movements for the first 24 to 48 hours of life, stools that are pale or clay colored, foul smelling or that float, infants that have salty-tasting skin, recurrent respiratory infections like pneumonia, coughing or wheezing, weight loss or low weight gain in childhood, diarrhea, delayed growth, and excessive fatigue.
Most patients are diagnosed by their first birthday but less severe cases sometimes aren't caught until after 18 years of age.Genetics: It's Written On Your Face
Patients usually die of lung complications. Other tests to help detect CF include: Sweat chloride test, which is the standard test for CF. High salt levels in the patients sweat is an indication of CF, Fecal fat test, upper GI and small bowel series, and measurements of pancreatic function. After a diagnosis has been made there are a number of treatments available, these include: Antibiotics for respiratory infections, pancreatic enzyme replacement, vitamin supplements mostly A, D, E, and Kinhalers to open the airways, enzyme replacement therapy which makes it easier to cough up the mucus, pain relievers, and in very severe cases, lung transplants.
Sickle cell anemia[ edit ] Sickle cell anemia is an inherited disease of the red blood cells which causes abnormally shaped red cells. A typical red blood cell has about million hemoglobin molecules, which bind with oxygen. In a person with sickle cell disease, one amino acid is changed in the hemoglobin molecule, and the end result is misshapen red blood cells.