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8. Chromosomal abnormalities
BrownMed
33
Accounting
Pre-School
11/02/2010

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Cards

Term
2 main types of translocations / 2 types of each of those
Definition
reciprocal and robertsonian; balanced or unbalanced
Term
balanced reciprocal translocation denotation
Definition
46,XX,t(5;8)
Term
t/f balanced chromosomal translocations are typically phenotypically normal
Definition
true
Term
unbalanced chromosomal translocations typically result in (3)
Definition
mental retardation, and/or congenital abnormalities in the fetus, or early pregnancy loss
Term
children of balanced translocation parents are usually
Definition
unbalanced translocations
Term
"derivative of chromosome 8" (2)
Definition
mostly chrom 8 with some of the translocated chromosome on it; does not know which chromosome to align with during meiosis, resulting in 3 possible pairings, two of which are nonviable (viable gametes are viable because they contain all the genetic material)
Term
alternate segregation
Definition
euploid gametes, half w/ normal chromosomes and half with both translocated chromosomes
Term
adjacent segregation
Definition
aneuploid gametes which die. each gamete gets one normal chromosome and one translocation chromosome with duplications and deletions
Term
how often do alternate segregations occur instead of adjacent segregations?
Definition
occur in about equal frequency
Term
metacentric
Definition
chromosome with equal arms
Term
sub-metacentric
Definition
centromere just off-center
Term
acrocentric
Definition
centromere is near an end
Term
robertsonian translocation
Definition
when the long arms of 2 acrocentric chromosomes fuse at the centromere, with loss or partial loss of short arms
Term
t/f the short arm regions of acrocentric chromosomes carry essential genes
Definition
false; robertsonian translocations result in normal phenotypes
Term
acrocentric chromosomes
Definition
13, 14, 15, 21, 22
Term
most common robertsonian translocation denotation
Definition
45,X?,der(13;14)
Term
robertsonian translocations result in _ conceptions
Definition
trisomic; example, 14;21 -> trisomy 21
Term
a mother with a rob. trans. w/ chrom 21 has a _% chance of having a baby with translocation Downs / father risk
Definition
10-15. risk is <1% for fathers who are rob. carriers
Term
risk for recurrence of trisomy 21 when a couple has a baby with translocation downs in which the translocation ocurred de novo in an egg or sperm before fertilization
Definition
very low
Term
chromosome trisomies that usually miscarry in the first trimester
Definition
14,15 or 22, so rob. trans. carrier = higher miscarriage risk
Term
deletions (4)
Definition
errors in chromosomal crossover during meiosis - chromosomal translocations - breaking without rejoining - crossover within a chromosomal inversion
Term
haploinsufficiency
Definition
loss of half of normal activity of a protein causes disease - microdeletion related
Term
which deletions are usually fatal
Definition
large deletions
Term
microdeletion 22
Definition
congenital heart defect, assymetric face, low calcium level
Term
segmental aneuploidy / may be due to (2)
Definition
= duplications / unequal crossing over, crossing over within an inversion loop
Term
charcot marie tooth disease
Definition
peripheral meuropathy, slow progressive weakness and atrophy of muscles. due to dup(17) -> myelin gene duplicated
Term
paracentric inversion
Definition
breakage and union within the same arm
Term
pericentric inversion
Definition
breakage and reunion on either side of the centromere
Term
dicentric
Definition
having two centromeres
Term
acentric
Definition
no centromeres
Term
which kind of inversion results in nonviable gametes? (dicentric/acentric)
Definition
paracentric inversions
Term
which kind of inversion results in higher risk for abnormal pregnancy, dups and dels?
Definition
pericentric
Term
chromosomal abnormalities in cancer (4)
Definition
translocations, deletions, duplications,, inversions
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