01:119:115 Lecture Notes - Lecture 10: Dihybrid Cross, X-Inactivation, Mendelian Inheritance
15 Mar 2016
School
Department
Course
Professor
Document Summary
Genes on x chromosome are important to females and males. In females, one x chromosome in each cell is inactivated during embryonic development (x inactivation in females: inactive x chromosome condenses into an object a barr body, therefore, at functional level, females are also hemizygous. Barr body is very dense, stains darkly and lies along inside of the nuclear envelope. Active x chromosome looks indistinguishable from other autosomes. Inacivation involes modification of dna and histone proteins (dna methylation occurs, i. e. attachment of methyl groups [-ch3] to dna nucleotides) Inactivation of x chromosome is random and independent in each embryonic cell at the time it is occurring: specific x that is active in any one cell may be different. Some genes involved in coat color in cats are x-linked. But, there are only 23 homologous pairs of chromosomes. Therefore, there must be many genes on any given chromosome (called linked genes)
