Lect 3 - Chromosomal disorders Flashcards
describe what is trisomy 21, what are its characteristics, and what are the risk factors?
trisomy 21 is a aneuploidy disease where there is an extra chromosome on chromosome 21 due to duplication in either egg or sperm.
suffers will have physical characteristics of protruding tongue and small ears. lower IQ, heart defects.
the main risk factor is maternal age, and genetic inheritance.
how do aneuploidies arise?
either in meiosis 1 or meiosis 2, when the sister chromatids fail to separately move to the spindle fibre ends. this is known as nondisjunction
why is aneuploidy on sex chromosomes more tolerated
x chromosome inactivation
smaller number of genes on y
genes on y are not needed for survival
what are 2 examples of sex chromosome aneuploidy diseases
Turner’s
Klinefelter
what are some of the ways chromosomal rearrangement can occur, what determines the impact of these
on a single chromosome, parts can be deleted (miss-pairing of segments), duplicated, or inverted (inversion loop).
on 2 chromosomes, parts can be inserted, or translocated.
most of the time, it is the size of the chromosomal rearrangement that determines the impact.
what are examples of chromosomal rearrangement diseases?
Cri Du Chat - larynx abnormality, high pitched cry
Prader-Willi - low muscle tone, short stature, over-eating
Is chromosome variation bad?
no, it is a part of evolution. we all have chromosomal abnormalities. these abnormalities can result in normal individual, carrier of disease, or genetic disease suffer.
