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CMD Block 2 > Abn in Chromosome Structure > Flashcards

Abn in Chromosome Structure Flashcards

1
Q

What are the 5 categories of chromosomal structural abnormalities?

A 
reciprocal translocation 
Robertsonian translocation
deletions
duplications
inversions
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2
Q

Type of chromosome with roughly equal sized long and short arms

A

metacentric

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3
Q

What is the difference between a submetacentric chromosome and an acrocentric chromosome?

A

the p arms of acrocentric chromosomes only contain tandem repeats of ribosomal RNA genes while the p arm of a submetacentric chromosome can contain any number of genes. It is just a chromosome in which the centromere is not located in the middle of the chromosome

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4
Q

short arm of chromosome

A

p

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5
Q

long arm of chromosome

A

q

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6
Q

What are the acrocentric chromosomes?

A

13, 14, 15, 21, 22

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7
Q

What is contained in the satellite of an acrocentric chromosome?

A

rRNA genes (tandem repeats)

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8
Q

At what phase of cell division will you achieve the best resolutions of chromosomes for examination (particularly of the banding patterns)?

A

metaphase

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9
Q

T or F: All structural abnormalities are detectable using light microscopy

A

false: abnormalities in very small segments (=submicroscopic )) require molecular approaches for detection

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10
Q

What are structural abnormalities in chromosomes?

A

one or more double stranded breaks in DNA that have been repaired incorrectly

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11
Q

Chromosomes without ______ will not be able to undergo cell division

A

centromeres or telomeres at each end

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12
Q

T or F: Chromosomes without a centromere are stable.

A

false: very unstable (same is true for cells without telomeres)

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13
Q

Describe a balanced chrom structural abnormality.

A

rearrangement of segments that results in the NET normal amount of genomic material

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14
Q

T or F: Indivs with balanced chrom abnormalities have normal phenotypes and do carry not any reproductive risks.

A

false: they will have normal phenotypes but DO CARRY reproductive risks

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15
Q

T or F: An individual with a balanced chromosomes abnormalities could have partial monosomy or trisomy

A

false: unbalanced

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16
Q

Describe an unbalanced chromosome abnormality.

A

rearrangement lets to extra or missing genetic material –> mono and trisomy

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16
Q

T or F: Unbalanced chrom abnormalities are unlikely to cause an abnormal phenotype

A

false: very likely to cause abn phenotype

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17
Q

T or F: balanced abnormalities always result in a normal phenotype.

A

F: usually does. If they rearrangement interrupts (deletes or duplicated) several genes it can lead to an abnormal phenotype

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18
Q

What structural abnormality results in 3 copies of a particular chromosome segment?

A

partial trisomy

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19
Q

What structural abnormality results in only one copy of a chromosome segment?

A

partial monosomy

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20
Q

What type of abnormalities are present in the offspring of normal parents?

A

de novo

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21
Q

T or F: A de novo structural abnormality is always unbalanced.

A

F: they can also be balanced (robertsonian)

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22
Q

What type of structural abnormality segregates trough a pedigree in balanced form and can occasionally give rise to an unbalanced offspring?

A

familial

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23
Q

What is a familial abnormality?

A

segregates through pedigree in balanced form but can occasionally give rise to an unbalanced offspring

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24
Q

What is a constitutional abnormality?

A

present in all cells of the body

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25
Q

What is an acquired abnormality?

A

arises in small group somatic cells (usually in a single tissue)

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26
Q

What is the difference between squired abnormalities and mosaicism ?

A

aquired = abn in malignant cells

mosaicism = mixed populations of non-malignant cells

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27
Q

In general, autosomal imbalance causes… (4)

A
  • intellectual disability
  • growth delay
  • dysmorphology
  • congenital organ defects
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28
Q

Does an imbalance in sex or autosomal chromosomes (generally) produce a more severe abn phenotype?

A

autosomal

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29
Q

T or F: the larger the imbalance the greater the risk of lethality.

A

true

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30
Q

T or F: Monosomy has greater phenotypic consequences than trisomy.

A

true

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31
Q

T or F: reciprocal translocations involves the exchange of segments between two homologous chromosomes.

A

False: non homologous chroms

What is translocation between homologous chromosomes????

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32
Q

What type of translocation involves the fusion of 2 centromeres?

A

robertsonian

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33
Q

How many strand breaks are required for reciprocal transolcation?

A

2 double stranded breaks

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34
Q

T or F: reciprocal translocation always result in a balanced carrier.

A

false: it can also give rise to chromosomes are are unstable and will be lost (i.e. 2 or 0 centromeres

35
Q

What is a centric fragment?

A

fragment that contains the centromere

36
Q

What is an acentric fragment?

A

fragment that does not contain a centromere

37
Q

T or F: When centric and acentric fragments exchange 2 stable chromosomes result.

A

False: both are unstable (1 will have 2 centromeres and the other won’t have any) (slide 15 in pre-study)

38
Q

T or F: When 2 acentric fragments are exchanged 2 stable chromosomes results

A

true (see slide 15 in pre-study for figure of this)

39
Q

How many mitotically stable chromosomes can robertsonian translocaton give rise to?

A

1

can you get 2 if only the acentric fragments exchange?

40
Q

What are the possible reproductive outcomes of a reciprocal translocation carrier?

A

normal
balanced carrier
partial trisomy
partial monosomy

41
Q

Describe the most likely segregation pattern for translocations (during meiosis).

A

gametes receive either the 2 normal or the 2 abnormal chromosomes so that when the genetically normal sperm or egg joins it, the offspring’s genetic material is balanced or completely normal

= Alternate pattern of segregation

42
Q

Describe the risk-associated pattern of segregation.

A

gamete receives one normal and one abnormal chromosome so that when the genetically normal sperm or egg joins, the offspring will be unbalanced (partial mono or trisomy)

= Adjacent pattern of segregation

43
Q

What type of translocation involves the long arm fusion of acrocentric chromosomes?

A

robertsonian translocation

44
Q

What is the total number of chromosomes for a balanced carrier?

A

45 (robertsonian) and 46 (reciprocal)

45
Q

T or F: Loss of acrocentric short arms has no phenotypic consequence

A

true (it has redundant genes)

46
Q

T or F: Robertsonian translocation can occur between chromosome 13 and 16.

A

F: 16 is not acrocentric

47
Q

T or F: The reproductive risks for individuals with robertsonian translocated chromosomes depends on the chromosomes involved

A

true

48
Q

Paracentric inversion results from ___

A

2 breaks in the same arm

49
Q

Pericentric inversion results from ____

A

2 breaks in different arms

50
Q

A ring chromosome results from _____

A

2 breaks in different arms/near the ends of the chromosomes

51
Q

What is the difference between a paraentric and pericentric inversion?

A

pericentric inversion includes the centromere and requires the breaks to be in different arms

paracentric inversion requires breaks in the same arm and does not include the centromere

52
Q

Interstitial deletion arises from _____

A

2 breaks in the same arm

53
Q

T or F: Inversons result in balanced chromosomes

A

true

54
Q

Do individuals with inverted chromosome segments have an increased reproductive risk? Why or Why not?

A

Yes, because the inverted chromosome could have issues pairing up during meiosis

55
Q

A terminal deletion arises from ____

A

a single break and loss of the broken terminal segment

56
Q

Will a chromosome with a terminal deletion be stable enough to undergo mitosis?

A

yes, but only because it will acuire a new telomere via “telomere healing”

57
Q

What is an isochromosome?

A

the centromere of sister chromatids transversely divide to give rise to abnormal chromosomes consisting of one with 2p and one with 2q

58
Q

What is the consequence of isochromosome formation during meiosis?

A

the gametes produced will conceive offspring with partial monosomy or partial trisomy ?? maybe??

58
Q

T or F: Duplications result in balanced chromosomes

A

false: unbalanced

58
Q

T or F: acquired abnormalities in chromosome structure are restricted to malignant cells?

A

true

58
Q

What structural abnormality is seen consistently in chronic myelogenous leukemia?

A

t(9, 22) = reciprocal translaction between 9 and 22

58
Q

_____ is typical in malignancy

A

genomic instability

58
Q

What is the most sensitive part of the body to chromosome imbalance?

A

nervous system

58
Q

T or F: With an unbalanced conceptive, there will be both partial monosomy and partial trisomy

A

True

58
Q

Ultimately, what are the possible outcomes of an unbalanced conceptive?

A
  • mild to severe phenotype

- spontaneous abortion

59
Q

What is the consequence of isochromosome formation during mitosis?

A

mosaicism with lines that are partial trisomics or partial monosomics?? maybe??

59
Q

What type of offspring does a balanced carrier most often give rise to?

A

balanced carrier

rarely, they will produce partial mono and trisomies (which would be in the same cell)

60
Q

What are the reproductive outcomes of a family with a balanced carrier?

A

normal
Balanced carrier
miscarriage (unbalanced and non-viable)
affected individual (unbalanced and viable)

61
Q

In reciprocal translocation events, what are the 3 categories of gametes produced? and what are their phenotypes?

A

normal –> normal
balanced –> normal
Unbalanced –> abnormal or miscarriage

62
Q

Does a bigger risk for abnormal offspring occur with large or small translocations?

A

small because they are more compatible with life (large translocations are usually non-viable and spontaneously abort)

63
Q

What is a spacial class of reciprocal translocations that involve the long are fusion of acrocentric chromosomes?

A

robertsonian translocation

64
Q

What are the only 2 viable n=45 abnomalities ?

A

robertsonian translocation

turners syndrome

65
Q

What are the 2 proceses by which an individual can develop down syndrome?

A

robertsonian translocation

non-disjunction

66
Q

T or F: robertsonian translocation leads to partial trisomy and partial monosomy.

A

F: full trisomy and full monosomy ** can ignore the short arm material (even though she said this was partial in the pre-study…)

67
Q

T or F: in robertsonian translocation, you can expect to see equal proportions of normal karyotyoe and balanced carrier

A

true

68
Q

There is a ___-fold increased risk of maternally-derived translocation carriers than paternally-derived carriers

A

10

69
Q

What are the only viable robertsonain chromosome translocations`?

A

13 or 21

70
Q

T or F: A robertsonian translocation resulting in trisomy 14 will have the most severe phenotype of all of the robertsonian derived trisomies?

A

false: 14 is not a viable trisomy (only 13 and 21 are)

71
Q

A Robertsonian translocation between homologous chromosomes can very closely resemble a(n) ______

A

isochromosome

72
Q

Will this individual be able to produce viable offspring?

45, XX, rob(14q14q)

A

No, the all of the gametes formed will be trisomy 14 or have no copy of 14 both of which are not viable

73
Q

Will this individual be able to produce viable offspring?

45, XX, rob(21q21q)

A

yes, but the child will have down syndrome

74
Q

Will this individual be able to produce viable offspring?

45, XX, i(21q)

A

yes, but the child will have down syndrome

75
Q

What is the phenotype of the following individual?

45, X, i(Xq)

A

turner’s syndrome (isoX chromosome = unbalanced)

76
Q

How are deletions and duplications diagnosed?

A

conventional karyotype
FISH
array CGH

77
Q

What are the indications for performing a chromosome analysis?

A
  • confirm recognized syndrome
  • family member of known case
  • multiple congenital abnormalities in fetus, stillborn, or infant
  • couples with multiple fetal losses
  • ambiguous genitalia or delayed puberty
  • mental retardation
  • prenatal Dx for maternal age or other indication

CMD Block 2 (38 decks)

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