Exam 2: X Chromosomes and Dosage Compensation Flashcards
the number of copies of a gene usually corresponds to…
the amount of gene expression
does gene “dosage” matter?
yes, more is not better
male mammals get how many doses of the x chromosome?
a single dose (copy)
female mammals get how many doses of the x chromosome?
a double dose (two copies)
is the double dose of X in females a problem?
it would be if we didn’t have dosage compensation
dosage compensation
shut down one copy of the x chromosome in females so both sexes only have one active X
equalizes effect of x-linked genes in males/females
in placental mammals when does random x-inactivation occur in females?
early in development
what happens in random x-inactivation?
one or the other of the two X chromosomes is shut down and becomes a barr body
barr body
an X chromosome that is high condensed, inactivated, and late-replicating
is x-inactivation in females a way of shutting off bad genes?
no, it is a random process
female mammals have ____ due to sex-linked genes
mixed phenotypes
every female mammal is an “x-chromosome expression mosaic”
dosage compensation in fruit flies
doubling output of the x in males equalizes the effect of x-linked genes in males/females
