Medicine is transforming rapidly. During this era of human history, scientists are forever changing lives, because for the first time humans are not powerless against their genes! We now have the power to not only predict, but also alter our very future. The Genetic Revolution is here!
With the power of gene therapy, scientists now have a new tool that enables them to change a patient's DNA. Medical treatments usually counteract the symptoms of a disease. But with gene therapy, doctors can cure diseases. Click to learn more
The concepts described in this website might be a review for some people, or it might be a new learning experience. Click in order to learn or review the basics of biology and genetics.
Medicine is transforming rapidly. During this era of human history, scientists are forever changing lives, because for the first time humans are not powerless against their genes! We now have the power to not only predict, but also alter our very future. The Genetic Revolution is here!
Genetic Disorders Basics
Genetic Disorders are problems caused by mutations or alterations in the genes of a person. There are many different types of genetic disorders. This page will be a guide to the basics of genetic disorders.
Single-gene: Single-gene inheritance, otherwise known as Mendelian or monogenic inheritance, is caused by changes (mutations) in the DNA sequence of one gene. This change can cause minuscule or severe damage based on the location of the gene.
Autosomal Dominant: In order to be affected by an autosomal dominant disorder, only one mutated copy of the gene will be needed. The person with the disease usually have at least one parent with the mutated copy. The chance that a child will inherit the gene is 50%. Although only one copy of this mutation is needed, only a small number of people who inherit the mutation will actually go on to develop the disease.
Autosomal Recessive: To receive an autosomal recessive disorder, two copies of the mutated gene must be received. The affected person usually have unaffected parents, each carrying a single copy of the mutation.
X-linked Dominant: An X-linked dominant disorder is caused by mutations in genes on the X chromosome. Both males and females are affected by these disorders. Females, however, are more frequently affected than males.There is a 50% chance that a woman with an X-linked dominant disorder will have an affected fetus with each pregnancy.
X-linked Recessive: These disorders are caused by mutations in genes on the X chromosome. Males are more frequently affected than females. A woman carrying an X-linked recessive disorder has a 50% chance of having sons who are affected, and a 50% chance of having daughters who will carry one copy of the mutated gene (making them carriers). Fathers cannot pass X-linked traits to their son.
Y-linked: These disorders are caused by mutations on the Y chromosome. Every son of an affected father will be affected. Female daughters of affected fathers are never affected.Because of the small size of the Y chromosome, there are not a lot of Y-linked disorders.
Codominant: In this inheritance, two different version of a gene can be expressed, each making a slightly different protein. Both of these "version" can influence the genetic trait or characteristics of the genetic condition.
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Video: Multifactorial Traits
These types of genetic disorders are caused by a multiple number of genes. This makes treatment extremely complicated, because some genes have a small effect regarding the disorders, while others play a much larger role. Multifactorial inheritance disorders can be triggered by environmental factors, multiple mutations in different genes, or a combination of both of these. Multifactorial inheritance is involved in traits such as fingerprint patterns, skin color, height, and eye color. The chance of a person receiving a multifactorial inheritance disorder depends greatly on the relation between them and the family members with the disorder. For example, a person is more likely to get the disorder if their mom has it, then if their cousin has it. Some multifactorial inheritance is more common in females than males, and vice verse.
Disorders of this nature involved entire chromosomes. Here are the following types:
Numerical Abnormalities: When a person is missing a chromosomes from a pair, it is called a monosomy. When a person has more then two chromosomes of a pair, it is called a trisomy.
Structural Abnormalities:
Deletion: A part of the chromosome is missing.
Duplication: There are extra genetic material on a chromosome because some of the parts were duplicated.
Translocations: Translocation is when part of one chromosome is transferred to another chromosome. When parts of two different chromosomes switch, it is called a reciprocal translocation. When an entire chromosome is attached to another chromsome at the centromere, it is called a Robertsonian translocation.
Inversions: Part of the genetic material of a chromosome is inverted as a portion of the chromosome breaks off, turned upside down, and then reattach itself.
Rings: Part of a chromosome breaks off and then form a ring(circle). May or may not lose genetic materials.
Egg or Sperm Abnormalities: These alterations happen on the egg or sperm, causing the abnormalities to be present in every cell of the body.
Mosaicism: Some abnormalities happen after contraception, resulting in some cells having the abnormalities and some to not have the abnormalities.
A very small number of chromosomal abnormalities can be inherited, but most are "de novo", newly developed in the individual.
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Watch this video on Chromosome Abnormalities
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This is a very rare type of genetic disorder that is caused by mutations in the non-chromosomal DNA of mitochondria.
All humans have a second genome that is located in cellular organelles called mitochondrias. They have circular pieces of DNA that can mutate just like any other DNA.
Mitochondrial related diseases are illness caused by a lack of mitochondria coding proteins. These proteins are usually involved in energy metabolism, so their deficiency could have some serious problems.
Mitochondrial diseases can be inherited from autosomal recessive genes (two copies needed) or autosomal dominant (only one copy of the gene is needed).
X-linked Recessive inheritance can also cause mitochondrial diseases. The defect is usually located on the X chromosome, and usually only affects males.
Some mitochondrial inheritances is caused by sporadic cases-- no relatives of the patient has the disease. This could be caused by both genetic and/or environmental changes.
Sometimes error in cell division can create too few or too many copies of chromosomes, resulting in a disorder.
Mitosis: Abnormalities can occur in mitosis, the duplication process of the original cell
Meiosis: Abnormalities can also occur in meiosis the process which creates half the number of chromosomes (these cells later develop into eggs or sperms).
These factors can increase the chance of newly developed chromosome abnormalities:
Maternal Age: Researchers believe that with time, errors can develop in an egg's genetic material. Therefore, women are more at risk of giving birth to babies with an abnormality, the older they are. This does not seem to affect men because they produce new sperms throughout their lives.
Environment: The environment be play a significant part in the occurrence of genetic errors.
Video: Mitosis and Mutations
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