what is non disjunction?
meiotic error
- homologous pairs fail to separate at anaphase I
- OR sister chromatids fail to separate
- OR homologous chromosomes may not remain together
what is aneuploidy?
chromosomes lacking or present in excess
how does a typical meiosis look like?
what are the two types of non disjunction
- first division nondisjunction
- second division non-disjunction
how are aneuploidy caused?
lack of cohesins which hold homologous pairs together
without cohesion, there is a high chance both homologs go to the same pole which will result in gamete having two of same chromosome or none
what is down syndrome aka trisomy 21?
3 copies of chromosome 21
- present in humans
- if resulting eggs is fertilized its trisomic
- if egg that did not receive a copy of chromosome 21 is fertilized its monosomic
what’s translocation 21 ?
- piece of chromosome breaks awat and attaches to another chromosome
- translocated piece of chromosome 21 plus two normal copies also has down syndrome
extra/ missing sex chromosomes have fewer effects than extra autosomes
T/F
T
what are karotypes XXX and XXY ?
- found among individuals in the normal, healthy range of physical and mental development
- most will not know they even have a genetic abnormality
describe Klinefelter XXY syndrome
describe turner XO syndrome
what is polyploidy?
complete extra sets of chromosomes
- triploid 3n- can prevent meiosis anaphase I disrupted
- tetraploid 4n
- even tighter ploidy levels - common in plant and fungi Eg- bread wheat hexaploidy
how does cancer occur ?
uncontrolled division of cells
name of the protein that appear and disappear in a cyclical fashion in cell cycle
cyclins
name of the enzyme that cyclins activate
cyclin dependent kinases CDKs
