Errors In Meiosis And X Inactivation Flashcards
What is trisomy 21
Down syndrome
Caused by an extra copy of chromosome 21
What is aneuploidy
Abnormal number of a chromosome
What age of mothers have 40% of all cases
45 and older
What is nondisjunction
Failure of a chromosome to seperate properly during anaphase of mitosis, meiosis 1&2
95% of Down syndrome babies have two maternal chromosome 21 (due to failure to seperate during meiosis)
What is klinfelter syndrome
Caused by nondisjunction resulting in gametes containing an extra X chromosome
Individual contains XXY genotype
Symptoms include female type pubic hair, wide hips, long legs arms, frontal baldness absent
What is turner syndrome
A chromosomal disorder in which a female is born with only one X chromosome
Resultant disorder from a gamete produced by chromosomal non disjunction
Symptoms include low stature, low hairline, elbow deformity, brown spots
If a pair of chromosomes fail to disjoin at anaphase of meiosis 1, what will the resulting gametes be
N+1, N+1, N-1, N-1
If a pair of sister chromatids fail to disjoin at meiosis 2, what will the resulting gametes be
N+1, N-1, N, N
What is polyploidy
Possession of more than 2 complete sets of chromosomes
Occurs when disjunction results gametes that have a complete set of duplicate chromosomes
What is chromosomal deletion
A deletion removes a chromosomal segment
What is chromosomal duplication
A duplication repeats a segment
What is a chromosomal inversion
An inversion reverses a segment within a chromosome
What is a chromosomal translocation
A translocation moves a segment from one chromosome to a non homologous chromosome (different type chromosomes)
What is Lejeune syndrome
Deletion of tip of short end of chromosome 5
What is Philadelphia translocation
a translocation between the long ends of chromosome 9 and 22 occurs (reciprocal translocation)
95% of patients with chronic myeloid leukaemia
Results in TK overexpression
