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CHROMOSOMES & CYTOGENETICS > ALL THE THINGS > Flashcards

ALL THE THINGS Flashcards

1
Q

What are the two numerical chromosomal abnormalities?

A

Polyploidy and aneuploidy

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2
Q

What is polyploidy?

A

affects 1% of conceptuses. Changes in the number of all chromosomes equally

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3
Q

What is aneuploidy?

A

affects 1 in 300 newborns. Changes in the number of one or multiple chromosomes (unequally)

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4
Q

What are some types of polyploidy?

A

triploidy and tetraploidy

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5
Q

What are some types of aneuploidy?

A

monosomy, trisomy, tetrasomy

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6
Q

Are numerical abnormalities of somatic chromosomes incompatible with human life?

A

NO!

Exceptions are 13, 18, 21

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7
Q

Numerical abnormalities where are more likely to be viable?

A

sex chromosomes

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8
Q

What is the most common origin for triploidy?

A

2 haploid sperm cells fertilize a haploid egg cell

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9
Q

What are two types of balanced structural chromosomal abnormalities?

A

translocation and inversion

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10
Q

What are two types of unbalanced structural abnormalities?

A

deletion and duplication

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11
Q

How does the DNA content “c” change during the cell cycle?

A

from 2c in G1 phase to 4c after S phase

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12
Q

What are the stages of Mitosis?

A

interphase, prophase, metaphase, anaphase, telophase, cytokinesis

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13
Q

What happens in prophase?

A

chromatin condenses into chromosomes

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14
Q

What happens in metaphase?

A

nuclear envelope disappears, chromosomes align at the equatorial plane

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15
Q

What happens in anaphase?

A

sister chromatids separate, centromeres divide

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16
Q

What is cohesin?

A

protein that holds the length of chromatids together

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17
Q

At what stage of mitosis, does cohesin bind to chromosomes?

A

prophase

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18
Q

At what stage of mitosis is cohesin removed?

A

metaphase

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19
Q

How is cohesin removed?

A

separase degrades it proteolytically at centromeres allowing separation of chromatids

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20
Q

At what stage of meiosis does crossing over occur?

A

Prophase I

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21
Q

In which meiosis are homologs separated?

A

Meiosis 1

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22
Q

In which meiosis are sister chromatids separated?

A

meiosis 2

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23
Q

Where can Mendel’s 3rd law be observed?

A

when homologs segregate independently in meiosis 1

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24
Q

What is cytogenetics?

A

study of human chromosomes, their structure, inheritance, and abnormalities

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25
Q

What is an individual’s chromosome constitution called?

A

karyotype

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26
Q

Describe the preparation of a karyotype

A

add phytohemagglutinin to stimulate T cell division; culture for 3 days; add colchicine to arrest cells in metaphase; spread cells onto slide by dropping; digest with trypsin then stain with Giesma; analyze the metaphase spread

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27
Q

What kind of banding pattern is seen after applying a Giemsa stain to chromosomes?

A

G-banding pattern

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28
Q

What is the p-arm of a chromosome?

A

short arm

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29
Q

What is the q-arm of a chromosome?

A

long arm

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30
Q

Where are the telomeres of a chromosome located?

A

at the ends

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31
Q

What is a metacentric chromosome?

A

centromere located in the middle

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32
Q

What is a submetacentric chromosome?

A

centromere is near the middle

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33
Q

What is an acrocentric chromosome?

A

centromere is located farther away from the middle

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34
Q

What are the important acrocentric chromosomes in humans?

A

13, 14, 15, 21, 22

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35
Q

What color are the bands after a chromosome is treated with Giemsa?

A

light and dark

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36
Q

Describe light chromosome bands

A

less condensed euchromatin that replicated early in S-phase

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37
Q

Describe dark bands

A

more condensed heterochromatin that replicates later in S-phase

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38
Q

You are given a chromosome location, 7 q 3 1 . 2; What information do you have here?

A

chromosome 7; q arm; region 3; band 1; sub-band 2

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39
Q

What do the symbols p and q mean when describing a karyotype?

A

short and long arm

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40
Q

What does cen mean?

A

centromere

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41
Q

What does del mean?

A

deletion

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42
Q

What does dup mean?

A

duplication

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43
Q

What does fra mean?

A

fragile site

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44
Q

What does i mean?

A

isochromosome

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45
Q

What does inv mean?

A

inversion

46
Q

What does ish mean?

A

in situ hybridization

47
Q

What does r mean?

A

ring

48
Q

What does t mean?

A

translocation

49
Q

What does ter mean?

A

terminal or end

50
Q

What does / mean?

A

mosaicism

51
Q

What does + or - mean?

A

indicates gain or loss of part of a chromosome

52
Q

What does 47, XX, +21 describe?

A

an extra copy of chromosome 21, trisomy 21 or Down syndrome

53
Q

For Case 7, the child with VSD and slow developmental milestones had what syndrome?

A

DiGeorge Syndrome

54
Q

Where is the deletion manifested in DiGeorge syndrome?

A

22 q 1 1

55
Q

What causes 95% of individuals to be born with complete trisomy?

A

meiotic nondisjunction

56
Q

What causes 4% of individuals to have Down Syndrome?

A

Robertsonian translocations

57
Q

What causes 1% of individuals to develop a mosaic form of trisomy 21?

A

mitotic nondisjuntion

– milder features

58
Q

What features are common for the clinical presentation of Down Syndrome?

A

dysmorphic facies, upward sloping palpebral fissures, over-folded helix

59
Q

What is nondisjunction?

A

failure of chromosomes or chromatids to segregate in M1 or M2

60
Q

Can nondisjunction occur in either the mother or father, with either autosomes or sex chromosomes?

A

Yes, hypothetically

61
Q

How many copies from one parent does an individual with trisomy receive?

A

2 copies instead of the usual 1

62
Q

If the two chromosomes from this parent are identical (2 copies of the maternal or paternal chromosome) then where did nondisjunction occur?

A

Meiosis 2

63
Q

If the two chromosomes from this parent are not identical (one maternal and one paternal chromosome) then where did the nondisjunction occur?

A

Meiosis 1

64
Q

How can you pinpoint where nondisjunction occurs in monosomy situations?

A

It is impossible to determine without knowing what the parent’s genotypes are

65
Q

Where does nondisjunction most often occur?

A

maternal meiosis 1

66
Q

Will an individual survive with polyploidy such as triploidy?

A

No. Will not make it to term

67
Q

For autosomal nullisomy (missing a pair of homlogs), where is the lethality assessed?

A

preimplantation

68
Q

For autosomal monosomy, where is the lethality assessed?

A

lethal in the embryonic stage

69
Q

For autosomal trisomy, where is lethality assessed?

A

usually embryonic or fetal lethal

70
Q

Which types of trisomy may survive to term?

A

Trisomies 13 and 18

71
Q

Are individual’s with trisomy 21 expected to survive? If so, for how long?

A

Yes, til age 40 or longer

72
Q

Name trisomies 13, 18, and 21

A

Patau syndrome, Edwards syndrome, Down syndrome

73
Q

What is the life expectancy of individuals with multiple X or Y chromosomes?

A

minor problems, normal lifespan

74
Q

Individuals at risk of having Turner’s syndrome have what complications before and after birth?

A

Born 45, X. 99% will abort spontaneously. survivors have normal intelligence, with infertility and minor physical abnormalities

75
Q

What is the clinical presentation of Patau syndrome?

A

cleft lip/palate; cardiac defects; genito-urinary and renal defects; mean survival 7 days

76
Q

What is the clinical presentation of individuals with Edwards syndrome?

A

microcephaly, CND and cardiac malformations, prominent occiput (back of head), micrognathia (undersized jaw), overlapping finger, rocker-bottom feet, median survival 14.5 days

77
Q

Turner’s syndrome is expressed how on a karyotype?

A

45, X

78
Q

In what pregnancy complication are cases of Turner’s syndrome commonly seen?

A

miscarriages (~99% of them)

79
Q

What is the clinical presentation of Turner’s Syndrome?

A

short stature, delayed pubertal development, amenorrhea

80
Q

How can the complications of Turner’s syndrome be treated?

A

Estrogen supplementation

81
Q

How is Klinefelter expressed on a karyotype?

A

47, XXY

82
Q

What is the clinical presentation for Klinefelter syndrome?

A

secondary sex characteristics display feminization; hypogonadims, infertility due to azospermia, disproportionately long limbs, tall thin stature

83
Q

How are the complications of Klinefelter treated?

A

Testosterone supplementation

84
Q

Does mental impairment increase or decrease as the number of X chromosomes increases in an individual?

A

increase

85
Q

What happens to the additional X chromosomes in individuals with trisomies, etc?

A

All but one of the X chromosomes is inactivated. The rest form Barr bodies

86
Q

Is there a gain or loss of genetic material with Balanced structural abnormalities?

A

No

87
Q

Is there a gain or loss of genetic material with Unbalanced structural abnormalities?

A

Yes

88
Q

Are individuals with balanced abnormalities generally affected?

A

No, unless the breakpoint occurs in or near a gene

89
Q

Are the offspring of individual’s with balanced abnormalities at risk?

A

Yes

90
Q

What are the two types of segregation that can occur during Meiosis?

A

alternate or adjacent segregation

91
Q

Can alternate/adjacent occur in Meiosis 1 and Meiosis 2?

A

No! Just in meiosis 1

92
Q

What kind of structural abnormality occurs from alternate segregation?

A

Balanced

93
Q

What kind of structural abnormality occurs from adjacent segregation?

A

unbalanced

94
Q

What is a translocation between 2 acrocentric chromosomes called?

A

Robertsonian translocation

95
Q

What is lost in a Robertsonian translocation?

A

p arms are lost

96
Q

What two things are retained in a Robertsonian translocation?

A

q arms and centromeres retained as fused chromosome

97
Q

What kind of structural abnormality do Robertsonian translocations represent?

A

Balanced

98
Q

What carrier karyotype is the most common for Down syndrome resulting from a Robertsonian translocation?

A

14 q 21 q

99
Q

A balanced 14 q 21 q carrier has a ___ risk of having a live-born child with Down syndrome

A

1/3 (Possibilities are Normal, Balanced carrier, or Trisomy)

100
Q

For 21 q 21 q balanced carriers, what are the 2 possible gametes?

A

Nullisomic for 21: monosomic offspring, lethal.

Disomic for 21: results in trisomy, Down syndrome

101
Q

___ % of live-born offspring of a 21 q 21 q balanced carrier will have down syndrome

A

100

102
Q

If 2 breaks occur in the same arm of a chromosome, what are the possible abnormalities that result? (What are the abnormalities called?)

A

Paracentric inversion

Interstitial deletion

103
Q

If 2 breaks occur in different arms of a chromosome, what are the possible abnormalities that result? (What are the abnormalities called?)

A

Pericentric inversion

Ring Chromosome

104
Q

Do Pericentric inversions involve the centromere?

A

Yes

105
Q

What is not involved in a paracentric inversion?

A

the centromere

106
Q

What are the two syndromes caused by autosomal deletions?

A

Wolf-Hirschhorn and Cri du Chat syndrome

107
Q

What chromosome region is deleted in Wolf-Hirschhorn Syndrome?

A

4p- (4 p 1 6 is the critical region)

108
Q

What facial abnormality is characteristic of Wolf-Hirschhorn syndrome?

A

broad flat nasal bridge, high forehead.

“Greek Warrior Helmet”

109
Q

What chromosome region is deleted in Cri du Chat syndrome?

A

5p-

110
Q

What is the common clinical presentation of Cri du Chat syndrome?

A

cat - like - cry

111
Q

What types of deletions are only detected via DNA probes?

A

Microdeletion syndromes

CHROMOSOMES & CYTOGENETICS (1 decks)

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