According to the University of Illinois at Chicago, the most common result of autosomal nondisjunction is Down syndrome. About 5000 individuals are born with Down syndrome each year. More »

As explained by DevBio, nondisjunction is what happens when a pair of chromosomes do not separate properly during meiosis. According to Indiana University-Purdue University Indianapolis (IUPUI), nondisjunction can occur ... More »

Nondisjunction occurs when chromosome pairs fail to separate during meiosis. As a result, gametes form having either too many or too few chromosomes, explains Education Portal. Offspring who inherit such gametes may exhi... More »

The pedigree diagram for Down syndrome typically lists three generations of family and shows any family members with the disease or indicators of it. Down syndrome is caused by an additional copy of the 21st chromosome. More »

Identical twins have the same DNA code because they are the result of an embryo splitting in half. Fraternal twins do not share the same DNA because they are a result of two separate embryos. More » Science Biology Molecular Biology & DNA

Freckles can be related to a dominant receptor gene for melanocortin-1, but they can also be the result of skin that is more sensitive to light. The skin cells that produce the pigment melanin are called melanocytes. The... More »

The two main sources of genetic variation are mutations and recombinations of genes as a result of sexual reproduction. A mutation is a permanent change in the DNA within a gene. More »