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Genetic Disorders

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Genetic disorders are a topic in biology that can not be avoided. The fact is that genetic disorders can happen in humans, plants or animal. No one and nothing is safe from a genetic disorder. A genetic disorder can appear in the first years off life, or can appear much later in life when least expected. A basic principal of biology states that the behavior of chromosomes during the meiosis process can account for genetic inheritance patterns. There are many reasons for genetic disorders.

To start it is important to understand what a genetic disorder is. It is a mutation in the genetic material of a person. The mutant gene is transmitted through

birth. These genetic mutations can create serious complications and even death.

It is important to understand how people get certain traits and genes. A person receives one set of chromosomes and genes from each person. That means each person inherits the traits. One gene may be more influential then another in developing specific traits. The more powerful gene is called the dominant gene and the less powerful is the recessive. A variation of a gene and the trait it controls, such as the color of ones eyes or hair is called in allele.

Most diseases have genetic disorders. A diseases springs from genetics that are passed along from the parents. So called genetic diseases can be classified in 3 ways single gene defects, chromosomal disorders and multi factorial. 1 in 200 births have single gene defects. There are over 6000 different known single gene disorders. These kind of disorders are characterized by the way they are carried through

a family.

In dominant inheritance the child of a carrier has a fifty percent chance of inheriting the gene. The parents of the children with genetic disorders are definitely carriers. While in recessive inheritance the parents do not necessarily have the gene. The chances vary with each generation of recessive genes. It also depends on the sex of the baby.

Recessive traits can only be expressed if both of the genes have the same mutation. Without both parents having the gene it is impossible for the disease to show up in their child. Although the child can have the recessive trait. That is homozygous traits. Heterozygous traits are apparent even if only one gene in a pair has the mutation.

Common recessive diseases are cystic fibrosis, sickle cell anemia, Tay Sachs.

Alzheimer and Huntington diseases are examples of dominant disorders. Some mutant disorders occur on the X chromosome. Females have little or no effects if the mutation occurs on the X linked gene. Males on the other hand do not have another X chromosomes so do not have another gene to fall on. Dominant disorders linked to the X chromosomes are usually very deadly to males. These disorders tend to affect men more then women. Almost exclusively. Some of the diseases associated with the X are down syndrome, Hemophilia. There are also the diseases that occur on the sex genes. They also come in recessive and dominant forms. With this it determines who will get the disease. For example a mother can pass on a trait to a daughter but not to a son and vice versa.

One can not forget that genetic disorders can also occur because of external effects. Things like cigarette smoking and drinking during pregnancy can affect the babies genetics. Leaving the baby with one of the genetic disorders.

Sickle cell anemia is a genetic disorder that usually appears between the ages of 2 and 4 years old. The red blood cells are shaped like crescents or sickles. The red blood cells only last about 10 to 24 days. In a healthy person they last about 120 days. That is where the anemia part of the name comes into play. Studies have shown that the people most prone to the disease are of Mediterranean or African decent. Although unhelpful in the United States in Africa it helped to combat against Malaria. Homozygous people have inherited the two copies of the gene making them prone for the disease. People who have inherited one copy of the gene are heterozygous. They are carriers of the trait but are not under immediate threat. However under certain circumstances their have been cases of people developing the disease from the recessive gene.

In simple terms in order for a person to have the disease both parents must have the trait. If only one parent has the disease there is a chance of the trait being passed on.

Huntington disease is a degeneration of the nervous system. It usually occurs in the older part of someone life. As the disease becomes worse it could cause uncontrollable movements in the body. Because the



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