Chromosomal Abnormalities Flashcards
genetic information is transmitted to daughter cells under 2 circumstances:
-mitosis - diploid replicates itself
-germ cells undergo meiosis - reduction of diploid (2n) to haploid state (1n) - when fertilized diploid state is restored to form zygote
what is mosaicisim? when does it occur?
the presence of 2 or more cell lines with different chromosome compositions in an individual
occurs bc of non-dysjunction after fertilization - when chromosomes don’t separate correctly
2 chromosome abnormalities?
numerical
structural
name 5 chromosome numerical abnormalities
euploidy
triploidy
tetraploidy
aneuploidy
monosomies
what is euploidy
chromosomal numeral abnormality
the addition of loss of complete sets of chromosomes - so the category of chromosomes changes
what is triploidy and what is it caused by?
possession of a complete extra set of chromosomes
caused by polyspermy (fertilization of an egg by more than 1 sperm)
sponatneously aborts
tetraploidy is a result of….
failure of the first zygotic division
lethal to the embryo
chromosomal numeral abnormality
what is aneuploidy
when does it occur?
the category of chromosome changes but does NOT involve whole sets
failure of a single chromosome to complete division
all autosomal __ are lethal in very early embryogenesis
they abort too early to even be recognized as a conception
monosomies
name 2 meiosis errors
homologs fail to separate (meiosis 1)
chromatids fail to separate (meisosis 2)
give 2 examples of autosomal aneuoploidies
down syndrome (Trisomy 21)
edwards syndrome (trisomy 18)
trisomy 18
edwards syndrome
aneuploidy
trisomy 21
downs syndrome
aneuploidy
karyotype for complete androgen insensitivity syndrome
46, XY
karyotype for triple X female
47, XXX
karyotype for klinefelter syndrome
47, XXY
karyotype for jacobs syndrome
47, XYY
true or false
the karyotype for klinefelter syndrome is 47, XYY
FALSE
47, XXY
Karyotype for Turner Syndrome
45, X0
random X-inactivation is established by the expression of what gene?
XIST gene
inactive X is coated by XIST RNA
once the XIST gene is expressed and the X is coated by XIST RNA, how is X inactivation maintained?
by methylation of DNA cytosine residues
explain what happens to females with turner syndrome
45, XO
they’re missing an X chromosome
they have delayed menarche and premature menopause
however, most of their offspring are chromosomally normal
men born with an extra X chromosome
klinefelter syndrome