Lecture 15: Errors in Meiosis & X-inactivation Flashcards
What is nondisjunction?
Failure of chromosomes to separate properly during meiosis
95% of down syndrome babies have two maternal chromosome 21
What is klinefelter syndrome XXY
individuals have an unusual number of sex chromosomes, two copy of an X and one Y.
Tall, feminine physique. Small testys
What is turner syndrome XO
Instead of two sex chromosomes they only have one. Physical manifestations, folds in the skin around the neck, some type of intellectual impairment, depends on where the x chromosome comes from.
If a pair of chromosomes fails to disjoin at
anaphase of meiosis I, what will be the likely
chromosome numbers (N) of the four resulting
gametes?
A) N+1, N+1, N, N.
B) N+1, N+1, N-1, N-1.
C) N+1, N-1, N, N.
D) N, N, N-1, N-1.
B) N+1 N+1 N-1 N-1 ??
if he said meiosis II the answer would have been C
What is polyploidy?
Possession of multiple sets of chromosomes
Creating a polyploid 4n raddage
each are going to produce gametes which is n=9 this hybrid has 18 chromosomes, if you treat the individuals so their gametes double you can produce a fertile raddage.
Cabbage has 2n = 18 chromosomes and turnip
has 2n = 20. Oil-seed rape is a polyploid derived
from these two Brassica species and is fully fertile. How many chromosomes would you
expect oil-seed rape to have?
A) 18
B) 19
C) 20
D) 38
D) 38 (because it is fertile)
what are the four chromosomal aberrations?
deletion
inversion
duplication
translocation
what is deletion?
a deletion removes a chromosomal segment
what is a inversion
an inversion reverses a segment within a chromosome
what is a duplication?
a duplication repeats a segment
what is translocation?
a translocation moves a segment from one chromosome to a non homologous chromosome
le jeune syndrome cri du chaat, what causes it?
deletion of tip of short arm of chromosome 5
Philadelphia translocation t (9:22)
95% of patients with chronic myeloid leukemia
TK overexpression:
Treatable with Gleevec in 90% of cases