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MHG - Exam 2 > Lecture 23-Cytogenetics 2 > Flashcards

Lecture 23-Cytogenetics 2 Flashcards

1
Q

Robertsonian translocation

A
  • exchange between whole arms of acrocentric chromosomes
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1
Q

With a balanced Robertsonian translocation how many chromosomes are you left with? Why?

A
  • 45: you lose the acentric arm material
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2
Q

With an unbalanced Robertsonian translocation how many chromosomes are you left with?

A
  • 46
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3
Q

Why are people with trisomies from translocations worrisome?

A
  • they can pass on the abnormal chromosome to their offspring
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4
Q

(T/F) People with Robertsonian translocations can have normal or non-normal children.

A

True. They are just subject to having more miscarriages due to monosomic zygotes

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5
Q

what is the most common robertsonian translocation?

A

13:14. 21 is also a fairly common participant

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6
Q

Recriprocal translocations

A
  • non-robertsonian translocation
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7
Q

With an unbalanced reciprocal translocation how many chromosomes are you left with?

A

46

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8
Q

With an balanced reciprocal translocation how many chromosomes are you left with?

A

46, very rarely 47

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9
Q

Although balanced translocations maintain the same amount of genetic material, they cause an increased likelihood of ______

A

miscarriages

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10
Q

what is a partial trisomy? partial monosomy?

A
  • when only part of a chromosome is duplicated into a third copy
  • when there is one full chromosome and only part of it’s homologous chromosome
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11
Q

What type of translocation carrier can potentially give rise to all types of children (unbalanced carrier, balanced carrier, unaffected)

A

someone with a balanced translocation

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12
Q

Inheritance of a familial translocation where carriers are phenotypically normal should result in what kind of phenotype?

A
  • normal
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13
Q

De novo mutation carriers have a ___% risk of unknown phenotypic abnormalities.

A
  • 10%
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14
Q

What will happen to conceptuses with small chromosomal imbalances? Large?

A
  • small: viable but abnormal

- large: abort

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15
Q

What are the 3 types of deletions?

A
  • terminal
  • interstitial
  • ring
16
Q

What is the problem with a ring deletion?

A
  • doesn’t go through mitosis well there are more problems than would be expected if just the ends were deleted but the ring structure hadn’t formed
17
Q

Microdeletion

A
  • <5Mb deletion which can be missed by G-band studies
18
Q

What are 4 examples of microdeletion syndroms?

A
  • Prader-Willi/Angelman
  • Rb
  • William
  • DiGeorge/Velocardiofacial
19
Q

How can you detect microdeletion syndromes? (3)

A
  • high resolution chromosome analysis
  • FISH
  • CGH array
20
Q

Isochromosome

A

When sister chromatids separate incorrectly and you’re left with 2 q or 2 p arms on one chromosome

21
Q

Isochromosomes are seen in what syndrome?

A

Turners

22
Q

Pericentric inversion

A
  • around centromere

- balanced rearrangement

23
Q

What is the abnormal recombinant of a pericentric inversion?

A
  • duplication of the p arm and deletion of the q arm
24
Q

Paracentric inversion

A
  • genes stay within p or q arms, and centromere not involved
25
Q

What is the abnormal recombinant in a paracentric inversion?

A
  • either 2 centromeres (doesn’t fare well during mitosis)
  • no centromeres (gets lost during mitosis)
  • almost never viable
26
Q

What does having a parent with an inversion mean for their potential offspring?

A
  • higher risk of having a duplication and deletion of parts of chromosome involved
27
Q

Mosaicism

A
  • presence in an individual or a tissue of at least two cell lines which differ karyotypically by are from a single zygote. Ex: some cells are trisomy 21 and some aren’t
  • can result from nondisjunction
28
Q

Severity of phenotype in mosaicism depends on _____(2).

A
  • tissue distribution of the abnormal cell line

- frequency of the abnormal cell line

29
Q

Mosaicism can be beneficial when _____

A
  • it results in trisomy rescue. When someone with trisomy from a meiotic nondisjunction has anaphase lag resulting in a normal cell, although, this normal cell would be the minority
30
Q

Confined placental mosaicism

- when did we start seeing this?

A
  • discrepancy between placental and fetal karyotype that can lead to false negatives or false positives for trisomies
  • after the advent of CVS
31
Q

~20% of the pregnancies with _______ have confined placental mosaicism.

A
  • idiopathic intrauterine growth retardation (small body)
32
Q

Uniparental disomy (UPD)

A
  • disomic cell line containing 2 chromosomes inherited from only one parent
  • usually the result of nondisjunction
33
Q

Why are UPDs dangerous?

A
  • because maternal and paternal DNA’s imprinting patterns are different
34
Q

Genomic imprinting involves modification of DNA during a critical period which can _____.

A
  • influence the expression of human genetic disorders and temporarily change gene expression contrary to mendelian principles
35
Q

What is the difference between Prader-Willi and Angelman’s syndrome? What are other ways we can get either of these syndromes.

A
  • PWS: is an interstitial deletion in the father’s chromosome 15 so there are 2 MATERNAL CHROMOSOMES
  • AS: Interstitial deletion in the mother’s chromosome 15 so there are 2 PATERNAL CHROMOSOME 15s
  • you can also get both of these by UPD
36
Q

CGH can detect what? what can’t it detect?

A
  • submicroscopic abnormalities down to individual bps

- cant tell you about balanced structural abnormalities which is fine because the concern is unbalanced translocations

37
Q

CMA is another name for _____

A

CGH

MHG - Exam 2 (11 decks)

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