01:119:115 Lecture Notes - Lecture 13: Barr Body, Organism, Drosophila Melanogaster
15 Oct 2018
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Document Summary
Dihybrid cross in pea plants and behavior of chromosomes during meiosis. Mendelian genes are at a specific loci on the chromosome. Chromosomes undergo segregation and independent assortment during meiosis. Xy must work together as a homologous pair although they are different. X-linked genes follow specific patterns of inheritance. The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. For a recessive x-linked trait to be expressed: a female needs two copies of the allele (homozygous, a male needs only one copy of the allele (hemizygous) X-linked recessive disorders are much moire common in males than in females. Examples: duchenne muscular dystrophy, hemophilia, color blindness (mostly x- linked) Recessive mutations are not usually expressed when only one copy of the allele is present: 50% chance that each son will have the disorder. One of the two x chromosomes in each cell is randomly inactivated during embryonic development.
