lecture 15 - errors in meiosis & X-inactivation Flashcards
What is nondisjunction.
Failure of chromosomes to separate during meiosis
If a pair of chromosomes fail to disjoin at anaphase of meiosis I, what will be the likely chromosome numbers of the four resulting gametes.
n+1, n+1, n-1, n-1
What do the terms aneuploidy and polyploidy mean?
aneuploidy: abnormal number of a particular chromosome
polyploidy: possession of multiple sets of chromosomes
Why are some polyploidy individuals sterile?
if the individual inherit an odd number of chromosome sets (3n, 5n, etc), usually infertile because chromosomes cannot pair up correctly during meiosis and no functional gametes can be produced
Why does X-inactivation occur in mammals?
when female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males
What is a Barr Body?
inactive X chromosome condensed in cells with more than one X chromosome
What leads to mosaic patterning.
random inactivation of X chromosomes
Outline why most genetic diseases do NOT show a mosaic effect in carrier females?
the gene products can move around the body
Describe an example of mosaic patterning in mammals.
different fur colour on cats
