Abn in Chromosome Structure Flashcards Preview

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Flashcards in Abn in Chromosome Structure Deck (86):
1

What are the 5 categories of chromosomal structural abnormalities?

reciprocal translocation
Robertsonian translocation
deletions
duplications
inversions

2

Type of chromosome with roughly equal sized long and short arms

metacentric

3

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

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

4

short arm of chromosome

p

5

long arm of chromosome

q

6

What are the acrocentric chromosomes?

13, 14, 15, 21, 22

7

What is contained in the satellite of an acrocentric chromosome?

rRNA genes (tandem repeats)

8

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

metaphase

9

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

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

10

What are structural abnormalities in chromosomes?

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

11

Chromosomes without ______ will not be able to undergo cell division

centromeres or telomeres at each end

12

T or F: Chromosomes without a centromere are stable.

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

13

Describe a balanced chrom structural abnormality.

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

14

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

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

15

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

false: unbalanced

16

Describe an unbalanced chromosome abnormality.

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

16

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

false: very likely to cause abn phenotype

17

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

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

18

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

partial trisomy

19

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

partial monosomy

20

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

de novo

21

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

F: they can also be balanced (robertsonian)

22

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

familial

23

What is a familial abnormality?

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

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