Genetics and Evolution

SLOS Chromosome SLOS is a metabolic disorder caused by a mutation in the DHCR7 (7-dehydrocholesterol reductase) gene on chromosome 11. This gene codes for an enzyme that is involved in the production of cholesterol. People who have SLOS are unable to make enough cholesterol to support normal growth and development.

Some people can curl up the sides of their tongue to form a tube shape. Tongue rolling is controlled by a single gene. However, people can learn to roll their tongue as they get older, suggesting that environmental factors also influences the trait.

Klinefelters syndrome is usually caused by nondisjunction of chromosomes. Nondisjunction happens when a pair of sex chromosomes fails to separate during egg (or sperm) formation. When an egg (or sperm) with an extra X chromosomes joins with a normal sperm (or egg), the resulting embryo will end up with three sex chromosomes (XXY) instead of the normal two (XX or XY). As the baby develops, the extra chromosome is then copied in every cell.

Chronic myelogenous leukemia is an uncommon type of cancer of the blood cells. The t(9;22) describes the Philadelphia chromosome, in which the bcr gene on chromosome 22 is juxtaposed to abl on chromosome 9.

This gene regulates calcium in melanocytes and is important in the process of melanogenesis.

ABO blood type antigens are not only found on the surface of red cells. They are also normally secreted in their body fluids, including saliva, tears and urine.

This type of human genetic disorder occurs when a change happens in part of a gene's DNA sequence. Genes make proteins, and a mutation in the gene will result in the protein not being able to function properly. Cystic fibrosis is an example of a single-gene disorder. Patients with the condition have a defective gene on chromosome 7 called CFTR.

This gene is the putative transforming gene of avian sarcoma virus 17. It encodes a protein which interacts directly with specific target DNA sequences to regulate gene expression.

Anticipation occurs in association with triplet repeat expansion mutations. The larger the expansion is, the earlier the onset and the more instable the mutation will be. Larger expansions therefore, present earlier in life, and are prone to further expansion in the next generation.

Non-penetrance means that a person has inherited the genetic change, but that it does not manifest the associated phenotype.

Oswald Avery was one of the pioneers of the scientific discipline of immunochemistry.

Human skin color ranges in variety from the darkest brown to the lightest pinkish-white hues. Human skin pigmentation is the result of natural selection. Skin pigmentation in human beings evolved primarily to regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects.

Alpha satellite DNA is a repetitive sequence known to be a major DNA component of centromeres in primates (order Primates).

XX male syndrome is a rare sex chromosomal disorder. Usually it is caused by unequal crossing over between X and Y chromosomes during meiosis in the father, which results in the X chromosome containing the normally-male SRY gene.