Introduction to Sex-linked Inheritance Flashcards
T/F. A female has two X chromosomes: one of paternal and one of maternal origin. However, w/ the exception of several X/Y homologous genes, one of these X chromosomes is inactivated in each somatic cell.
True.
What is the reason for X inactivation in female?
This mechanism ensures that the quantity of most X - linked gene products generated in somatic cells of the female is equivalent to the amount produced in male cells.
T/F. In the process of inactivation, the selection between the maternal and paternal X homologues is random, although once established, the same homologue becomes inactivated in each daughter cell.
True
T/F. The X chromosome in males remains active in every somatic cell and so any mutant X allele will always be expressed in a male.
True.
A male has only one X chromosome & hence only one copy of each X - linked gene. A male is said to be ____ in these X-linked genes.
hemizygous
Fathers can transmit X - linked genes to their sons.
False. Each son must receive his father ’s Y chromosome and not his X chromosome. Hence, fathers cannot transmit X - linked genes to their sons.
During meiosis, the X and Y chromosomes undergo synapsis only within the small pairing regions at the distal ends of their chromosome arms called ____.
pseudoautosomal
T/F. Aside from the pseudoautosomal regions, the rest of the XY bivalent remains condensed in pachytene where crossing - over in the non - pairing regions is normally inhibited.
True.
____ w/c are closest to the (non - pairing) sex determinants show partial sex linkage, while those that are the most distal show 50% recombination & therefore appear to be transmitted as ____.
Yp sequences; autosomal sequences
Occasionally, pedigree patterns of sex-linked traits may be mimicked by autosomal traits that show ____. For instance, ____ is generally autosomal dominant w/ female sex limitation.
sex limitation; familial breast cancer
