meiosis errors Flashcards
define aneuploid
an aneuploid cell is one which has an abnormal number of chromosomes
define polyploid
a polyploid cell formed from two gametes which has 2n number of chromosomes forming a tetraploid zygote
why are woman stripy, define and describe x inactivation
Only 1 x chromosome can be active at once. woman have 2 X chromosomes. at 4 days gestation 1 x in each cell deactivates and becomes a barr body.
This stays deactivated throughout replication of the cell.
define non-disjuction
the failuer of seperation of chromosome or chromatids during meiosis.
if at M1 n-1 n-1 n+1 n+1
if at M2: n n n-1 n+1
what are the three types of aneuploid syndroms talked about in the lecture
klinefelter syndrome: XXY
male at birth, lower brain function, feminin features
turners syndrome: XO
female at birth, poor brain function, effected by ma/paternal chromosome
down syndrome: 21 chromosomes has a third copy, causes poor brain function, increased risk as maternal age increases
what are the four types of chromosomeal errors which can occour
deleation: the removal of a section of a chromosome
duplication: the repition of a section of a chromosome. offten involved with mutations
inversion: When a section of a chromosome flips, causes problmes with reproduction as synapsing of homologous chromosomes have misaligned genes
translocation: When one part of a gene is embedded onto annother. not always reciprocated.
what is the difference between familal and regular down syndrome
down syndrome there are 3 compleate copys of chromosome 21. in familial down syndrom 14 and 21 have translocated, giving an effective 3rd chromosome 21 14 hybrde which causes the same symptoms as down syndrom
what is the name of the formation of an inactive x chromosome, how many do you have.
barr body
inactive hetrochromitain
number of X chromosomes - 1 = number of barr bodys.
Why can polyploids be used for self fertilization
re reproduce homologous chromosomes must align and synapes with pairing chromosomes. polyploids which come from 2 gametes (diffrent locations or same) with 2n chromosomes mean all chromosomes will have a pairing chromosome present
why is it challanging for 3n polyploids to replicate
when homologous chromosomes align, one chromosome of each type is left without a pairing chromosome. this causes the gamete produced to have a variable number of chomosomes.
what are the two disorders caused by chromosomal abnormalitys deleation and translocation
Cri de chat: the deleation of the tip of chromosome 5. early death. interlectual impearment.
philadelphia chromosome: translocation of chromosome 9 and 22. over represnetation of TK, higher likely hood of lukimia
