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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
What is a constitutional abnormality?
present in all cells of the body
25
What is an acquired abnormality?
arises in small group somatic cells (usually in a single tissue)
26
What is the difference between squired abnormalities and mosaicism ?
aquired = abn in malignant cells mosaicism = mixed populations of non-malignant cells
27
In general, autosomal imbalance causes... (4)
- intellectual disability - growth delay - dysmorphology - congenital organ defects
28
Does an imbalance in sex or autosomal chromosomes (generally) produce a more severe abn phenotype?
autosomal
29
T or F: the larger the imbalance the greater the risk of lethality.
true
30
T or F: Monosomy has greater phenotypic consequences than trisomy.
true
31
T or F: reciprocal translocations involves the exchange of segments between two homologous chromosomes.
False: non homologous chroms | What is translocation between homologous chromosomes????
32
What type of translocation involves the fusion of 2 centromeres?
robertsonian
33
How many strand breaks are required for reciprocal transolcation?
2 double stranded breaks
34
T or F: reciprocal translocation always result in a balanced carrier.
false: it can also give rise to chromosomes are are unstable and will be lost (i.e. 2 or 0 centromeres
35
What is a centric fragment?
fragment that contains the centromere
36
What is an acentric fragment?
fragment that does not contain a centromere
37
T or F: When centric and acentric fragments exchange 2 stable chromosomes result.
False: both are unstable (1 will have 2 centromeres and the other won't have any) (slide 15 in pre-study)
38
T or F: When 2 acentric fragments are exchanged 2 stable chromosomes results
true (see slide 15 in pre-study for figure of this)
39
How many mitotically stable chromosomes can robertsonian translocaton give rise to?
1 | can you get 2 if only the acentric fragments exchange?
40
What are the possible reproductive outcomes of a reciprocal translocation carrier?
normal balanced carrier partial trisomy partial monosomy
41
Describe the most likely segregation pattern for translocations (during meiosis).
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
Describe the risk-associated pattern of segregation.
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
What type of translocation involves the long arm fusion of acrocentric chromosomes?
robertsonian translocation
44
What is the total number of chromosomes for a balanced carrier?
45 (robertsonian) and 46 (reciprocal)
45
T or F: Loss of acrocentric short arms has no phenotypic consequence
true (it has redundant genes)
46
T or F: Robertsonian translocation can occur between chromosome 13 and 16.
F: 16 is not acrocentric
47
T or F: The reproductive risks for individuals with robertsonian translocated chromosomes depends on the chromosomes involved
true
48
Paracentric inversion results from ___
2 breaks in the same arm
49
Pericentric inversion results from ____
2 breaks in different arms
50
A ring chromosome results from _____
2 breaks in different arms/near the ends of the chromosomes
51
What is the difference between a paraentric and pericentric inversion?
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
Interstitial deletion arises from _____
2 breaks in the same arm
53
T or F: Inversons result in balanced chromosomes
true
54
Do individuals with inverted chromosome segments have an increased reproductive risk? Why or Why not?
Yes, because the inverted chromosome could have issues pairing up during meiosis
55
A terminal deletion arises from ____
a single break and loss of the broken terminal segment
56
Will a chromosome with a terminal deletion be stable enough to undergo mitosis?
yes, but only because it will acuire a new telomere via "telomere healing"
57
What is an isochromosome?
the centromere of sister chromatids transversely divide to give rise to abnormal chromosomes consisting of one with 2p and one with 2q
58
What is the consequence of isochromosome formation during meiosis?
the gametes produced will conceive offspring with partial monosomy or partial trisomy ?? maybe??
58
T or F: Duplications result in balanced chromosomes
false: unbalanced
58
T or F: acquired abnormalities in chromosome structure are restricted to malignant cells?
true
58
What structural abnormality is seen consistently in chronic myelogenous leukemia?
t(9, 22) = reciprocal translaction between 9 and 22
58
_____ is typical in malignancy
genomic instability
58
What is the most sensitive part of the body to chromosome imbalance?
nervous system
58
T or F: With an unbalanced conceptive, there will be both partial monosomy and partial trisomy
True
58
Ultimately, what are the possible outcomes of an unbalanced conceptive?
- mild to severe phenotype | - spontaneous abortion
59
What is the consequence of isochromosome formation during mitosis?
mosaicism with lines that are partial trisomics or partial monosomics?? maybe??
59
What type of offspring does a balanced carrier most often give rise to?
balanced carrier rarely, they will produce partial mono and trisomies (which would be in the same cell)
60
What are the reproductive outcomes of a family with a balanced carrier?
normal Balanced carrier miscarriage (unbalanced and non-viable) affected individual (unbalanced and viable)
61
In reciprocal translocation events, what are the 3 categories of gametes produced? and what are their phenotypes?
normal --> normal balanced --> normal Unbalanced --> abnormal or miscarriage
62
Does a bigger risk for abnormal offspring occur with large or small translocations?
small because they are more compatible with life (large translocations are usually non-viable and spontaneously abort)
63
What is a spacial class of reciprocal translocations that involve the long are fusion of acrocentric chromosomes?
robertsonian translocation
64
What are the only 2 viable n=45 abnomalities ?
robertsonian translocation | turners syndrome
65
What are the 2 proceses by which an individual can develop down syndrome?
robertsonian translocation | non-disjunction
66
T or F: robertsonian translocation leads to partial trisomy and partial monosomy.
F: full trisomy and full monosomy ** can ignore the short arm material (even though she said this was partial in the pre-study...)
67
T or F: in robertsonian translocation, you can expect to see equal proportions of normal karyotyoe and balanced carrier
true
68
There is a ___-fold increased risk of maternally-derived translocation carriers than paternally-derived carriers
10
69
What are the only viable robertsonain chromosome translocations`?
13 or 21
70
T or F: A robertsonian translocation resulting in trisomy 14 will have the most severe phenotype of all of the robertsonian derived trisomies?
false: 14 is not a viable trisomy (only 13 and 21 are)
71
A Robertsonian translocation between homologous chromosomes can very closely resemble a(n) ______
isochromosome
72
Will this individual be able to produce viable offspring? | 45, XX, rob(14q14q)
No, the all of the gametes formed will be trisomy 14 or have no copy of 14 both of which are not viable
73
Will this individual be able to produce viable offspring? | 45, XX, rob(21q21q)
yes, but the child will have down syndrome
74
Will this individual be able to produce viable offspring? | 45, XX, i(21q)
yes, but the child will have down syndrome
75
What is the phenotype of the following individual? 45, X, i(Xq)
turner's syndrome (isoX chromosome = unbalanced)
76
How are deletions and duplications diagnosed?
conventional karyotype FISH array CGH
77
What are the indications for performing a chromosome analysis?
- 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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