DNA Abnormalities that Manifest as Disorders Essay Example

Reference, 2007). This substitution causes their red blood cells to become distorted and take on a sickle-like shape. These distorted cells are unable to effectively carry oxygen and can sometimes block blood vessels. This genetic disorder leads to anemia due to the low oxygen capacity and short lifespan of the sickled red blood cells. The cause of this disorder is a single base substitution in which a normal amino acid, valine, is replaced by glutamine.

There are three mechanisms that contribute to genetic variation during meiosis and fertilization, which can lead to chromosome abnormality in the offspring of two healthy individuals. These mechanisms include independent assortment of chromosomes, crossing over, and random fertilization. Chromosome disorder can arise within these processes. One main cause of chromosomal abnormalities is meiotic nondisjunction, where chromosomes fail to separate and move to opposite poles during either the first or second meiotic division (Tissot & Kaufman, 2007). This failure can result in conditions such as trisomy, where there are three chromosomes instead of the usual two.

Down syndrome, also known as trisomy 21, is a well-known example of a human disease caused by autosomal nondisjunction. Some individuals affected by trisomy 21 survive (Tissot ; Kaufman, 2007). Trisomy 21 is characterized by the presence of an extra chromosome 21. Common characteristics of individuals with Down syndrome include oblique eye fissures with epicanthic skin folds at the inner corner of the eyes, poor muscle tone, a flat nasal bridge, a single palmar fold (also called a simian crease), a protruding tongue due to a small oral cavity and an enlarged tongue near the tonsils, a short neck, white spots on the iris called Brushfield spots,

excessive joint flexibility,
congenital heart defects, increased space between the first and second toe,
a single flexion furrow on the fifth finger,
and a higher number of ulnar loop dermatoglyphs (Wikipedia,
2007). Mental retardation commonly accompanies Down syndrome.
Certain DNA abnormalities can determine an individual's likelihood of developing specific diseases. While some minor DNA abnormalities may not cause immediate issues,
they can increase an individual's chances of developing certain diseases.

Comparing abnormal genes to normal genes allows scientists to identify slight differences in genes. Recent technological advancements, such as southern blotting and polymerase chain reaction, have made it possible to detect genetic disorders before they manifest as diseases. One example of this is the search for the gene responsible for hereditary nonpolyposis colorectal cancer (HNPCC), a significant form of colon cancer. Individuals inheriting the HNPCC gene face an 80% or higher risk of developing colon cancer and other cancers at an early age (Patlak, 2003). Furthermore, women with this gene are significantly more susceptible to uterine and ovarian cancer (Patlak, 2003). By applying the same principle, scientists can isolate specific genetic traits commonly observed among individuals affected by a particular disease.

The analysis of this gene's vulnerability to the disease provides an opportunity to forecast and avert its occurrence or develop a genetic remedy.