Sex chromatin and Lyon hypothesis

Question 1

Sex Chromatin

Answer 1

small condensed mass (heterochromatin) of inactivated X-chromosome usually
located just inside nuclear membrane of interphase ncl; number of sex chromatin
bodies per nucleus is one less than number of X-chromosomes

Question 2

AKA barr body

Answer 2

the inactive X chromosome in female somatic cell, rendered
inactive in process called lyonization.
Females have 1, males have none.

Question 3

Lyon Hypothesis

Answer 3

Explains phenotypic effect of why females with two x chromosomes and male wiht one are same.

Hypothesis that one X-chromosome is inactive during interphase in normal
females + is represented in interphase cell ncl as sex chromatin body.
presence or absence of Y determines male or female sex. Y chromosome
contains the gene SRY, which triggers testis development. Y chromosome shorter
than X.