Flashcards in Mutations/Chromosomal abnormalities Deck (49)
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Triplet repeat expansion in the X chromosome
Fragile X syndrome
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Male pt shows high forehead, large ears, long face and prominent jaw. Pt additionally has learning disabilities. Further physical exam shows large testes, conn. tissue weakness and mitral valve prolapse
Fragile X syndrome
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47 XXY
Klinefelter syndrome
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Although females have another X to compensate for X link recessive disorders, which condition still can have features show in the female?
Fragile X syndrome
Female carrier can show the characteristic facial features which include high forehead, large ear, long face and prominent jaw
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Pt presents with mild learning disability, reduce IQ, and exhibits self obsessed behavior. What karotype do you expect?
47 XXY
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Pt with reduced IQ and gynecomastia. How would you treat?
pt is XXY
treat with testosterone starting in puberty
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Conditions seen more commonly with increasing maternal age?
Klinefelter syndrome
Down syndrome
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You notice short arms on chromosomes are lost in FISH test. whats going on?
Robertsonian translocation
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Acrocentric chromosome
centrosome is on the end
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Two acrocentric chromosomes combine and lose their satellite arms. what happens to those arms in Robertsonian translocation?
those arms contains redundant rRNA, no harm there
usually considered functionally balanced since no genetic information is lost
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When can issues arise with Robertsonian translocations?
Issues can arise during chromosome segregation in meiosis I
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With pachytene quadrivalents, how many outcomes can there be?
6 possible
normal, balanced or unbalanced
1 normal
1 carrier
4 unbalanced
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what are the two situations that result in Down syndrome
Robertsonian Translocation to 14/21 and 21
or Trisomy 21 from non disjunction in maternal meiosis I
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You deliver a baby and it sounds like a cat!!! Whats wrong with his chromosomes?
deletion in terminal portion of chromosome 5
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Duchenne muscular dystrophy
microdeletion on X chromosome (Xp21)
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How do unbalanced insertions occur?
if material has moved within the same chromosome complement then one has a duplication and other is now missing that region
so technically, its an insertion and deletion
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pericenteric inversion
involves the centromere
genes flip around the centromere
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paracenteric inversions
gene swap happens in the arms
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2 or more genetically distinct cell lines derived from more than one zygote
Mixoplody - chimerism
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2 or more cell lines that differ in genetic constitution that are derived from a single zygote
Mixoploidy - Mosaicism
accounts for 1-2% of Down syndrome
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how frequent are chromosomal abnormalities in mature oocytes?
25%
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____ of all spermatozoa contain chromosomal abnormalities
10%
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Meiosis definition
process of nuclear division marking the final stage of gamete formation
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how does meiosis differ from mitosis?
mitosis results in 2 daughter cells, each diploid
meiosis halves the number creating 4 haploid gametes
meiosis only in the final stages of gamete formation
occurs in 2 distinct cell division events (I and II)
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Meiosis I starts with and ends with?
starts with diploid cell with replicated and condensed chromosomes (XX)
ends with haploid cells with pairs of sister chromatids (X) and (X)
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Meiosis II starts with and ends with?
starts with haploid cells with pairs of sister chromatids (X) and (X)
ends with four haploid cells with individual chromosomes ( I ) ( I ) ( I ) ( I )
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homologous recombination
also called Cross-over
allows genetic variation in resulting offspring
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what must occur for homologous recombination to occur?
chromosomes must synapse to form a bivalent (pair) for meiotic recombination to occur
errors in this process are a frequent cause of chromosomal abnormalities - translocations and inversions
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Example numerical of chromosomal abnormality
Aneuploidy
which is loss or gain of one or more chromosomes
Polyploidy - addition of one or more complete haploid complements
Monosomy - loss of a chromosome
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