Mutations/Chromosomal abnormalities Flashcards

(49 cards)

0
Q

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

A

Fragile X syndrome

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1
Q

Triplet repeat expansion in the X chromosome

A

Fragile X syndrome

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2
Q

47 XXY

A

Klinefelter syndrome

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3
Q

Although females have another X to compensate for X link recessive disorders, which condition still can have features show in the female?

A

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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4
Q

Pt presents with mild learning disability, reduce IQ, and exhibits self obsessed behavior. What karotype do you expect?

A

47 XXY

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5
Q

Pt with reduced IQ and gynecomastia. How would you treat?

A

pt is XXY

treat with testosterone starting in puberty

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6
Q

Conditions seen more commonly with increasing maternal age?

A

Klinefelter syndrome

Down syndrome

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7
Q

You notice short arms on chromosomes are lost in FISH test. whats going on?

A

Robertsonian translocation

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8
Q

Acrocentric chromosome

A

centrosome is on the end

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9
Q

Two acrocentric chromosomes combine and lose their satellite arms. what happens to those arms in Robertsonian translocation?

A

those arms contains redundant rRNA, no harm there

usually considered functionally balanced since no genetic information is lost

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10
Q

When can issues arise with Robertsonian translocations?

A

Issues can arise during chromosome segregation in meiosis I

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11
Q

With pachytene quadrivalents, how many outcomes can there be?

A
6 possible 
normal, balanced or unbalanced 
1 normal 
1 carrier 
4 unbalanced
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12
Q

what are the two situations that result in Down syndrome

A

Robertsonian Translocation to 14/21 and 21

or Trisomy 21 from non disjunction in maternal meiosis I

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13
Q

You deliver a baby and it sounds like a cat!!! Whats wrong with his chromosomes?

A

deletion in terminal portion of chromosome 5

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14
Q

Duchenne muscular dystrophy

A

microdeletion on X chromosome (Xp21)

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15
Q

How do unbalanced insertions occur?

A

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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16
Q

pericenteric inversion

A

involves the centromere

genes flip around the centromere

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17
Q

paracenteric inversions

A

gene swap happens in the arms

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18
Q

2 or more genetically distinct cell lines derived from more than one zygote

A

Mixoplody - chimerism

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19
Q

2 or more cell lines that differ in genetic constitution that are derived from a single zygote

A

Mixoploidy - Mosaicism

accounts for 1-2% of Down syndrome

20
Q

how frequent are chromosomal abnormalities in mature oocytes?

21
Q

____ of all spermatozoa contain chromosomal abnormalities

22
Q

Meiosis definition

A

process of nuclear division marking the final stage of gamete formation

23
Q

how does meiosis differ from mitosis?

A

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)

24
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)
25
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 )
26
homologous recombination
also called Cross-over allows genetic variation in resulting offspring
27
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
28
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
29
What is an example of a structural chromosome abnormality?
these are rearrangements resulting from chromosome breakage and subsequent reunion in different configuration includes translocations, inversions, deletions, and insertions
30
Trisomy 21 most frequently occurs from
non disjunction in the maternal meiosis I
31
Non disjunction in Meiosis I results in
two disomic gametes and two nullisomic gametes
32
Non disjunction in Meiosis II results in
1 Disomic gamete 1 Nullisomic gamete 2 normal monosomic gametes
33
XXX is an example of ? and what the are symptoms?
polyploidy no overt symptoms but there is a mild reductio in IQ and oppositional behavior due to maternal non disjunct in meiosis I
34
what would you suspect of a patient showing a reduction in IQ and emotional immaturity with FISH karotype showing chromosome evident of a paternal non disjunction in meiosis II
XYY male YY never split during gamete formation
35
Pt shows neck webbing and puffy extremities. You notice short stature for her age and normal intelligence but unusual social skills. What symptoms would you expect her to have later in life?
She is XO, has turner syndrome | she would have ovarian failure and narrowing of the aorta later in life
36
Does the inheritance of the X in Turner syndrome make any difference to the offspring?
yes, paternal X Turner pts show higher social cognition skills
37
45 X
Turner syndrome
38
In reciprocal translocations, when do issues usually arise?
during chromosomal segregation in meiosis I
39
If fragments exchanged in reciporal translocation are relatively equal then
there are generally no deleterious effects in the CARRIER
40
Reciprocal translocation
breakage of at least 2 chromosomes and exchange of fragments
41
Reciprocal translocations in Meiosis I
cannot form bivalents due to translocation forming a pachytene quadrivalent where each chromosome aligns with homologous material
42
Pachytene Quadrivalents
pattern of segregation determines is the haploid is normal, balanced or unbalanced. Normal (1/6) Balanced (1/6) Unbalanced (4/6)
43
Microdeletion on chromosome 15 (15q11-13) results in
Prader Willi syndrome or Angleman
44
Angelman Syndrome
deletion on maternal chromosome 15
45
Prader Willi syndrome
deletion of paternal chromosome 15
46
You deliver a floppy baby who wont eat. Years later, mother brings in an overweight toddler showing learning disabilities. What could be the condition?
Angelman or Prader Willi syndrome
47
What is Prader willi/ Angelman an example of?
Imprinting - this is where the gene/region shows different expression depending on parent of origin this is believed to be due to differences of methylation of DNA
48
Angelman syndrome characterized by
inappropriate laughter, ataxia and severe learning disabilities