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Genetics > Cytogenetics - 2 lectures > Flashcards

Cytogenetics - 2 lectures Flashcards

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Biology 101 flashcards
1
Q

accounts for large number of spontaneous abortions

A

chromosomal abnormalities

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2
Q

types of numerical chromosomal abnormalities

A

euploidy (polyploidy): number of chromosomes is in multiples of 23 –>triploidy (69) so has 3 copies or tetraploidy (92) so has 4 copies

aneuploidy: monosomy or trisomy

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3
Q

are euploidy compatible with life

A

nah

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4
Q

three common autosomal aneuploidy

A 
trisomy 21 (Down Syndrome)
trisomy 18 (Edward Syndrome)
trisomy 13 (Patau Syndrome)
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5
Q

two sex chromosome aneuploidy

A 
Turners Syndrome (45X)
Klinefelters Syndrome (47XXY)
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6
Q

most common liveborn autosomal trisomy

A

Down Syndrome

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7
Q

risk factors of Downs

A

increased maternal age increases risk of meiotic nondisjunction during oogenesis (with meiotic I nondisjunction being more common)

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8
Q

features of Downs

A

short, intellectual disability, congenital heart defects, single palmar crease, epicanthal folds, depressed nasal bridge, upslanting palpebral fissure

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9
Q

persons with downs is likely to develop what disorder and why

A

Alzheimers at a much younger age because genetic factors for alzheimers are on chromosome 21

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10
Q

what is chromosomal number for down syndrome

A

47, XX or XY, +21

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11
Q

features of edwards

A

clenched fist with overlapping fingers, rocker bottom feet, low set ears, smaller jaw (micrognathia), congenital heart defects, microcephaly, intellectual disability

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12
Q

genetic mechanism of edwards and patau

A

nondisjunction during oogenesis

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13
Q

chromosomal number of edwards

A

47, XX or XY, +18

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14
Q

features of patau

A

polydactyly, cleft lip and palate, microphthalmia, microcephaly, cardiac abnormalities, intellectual disability

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15
Q

chromosomal number of patau

A

47, XY or XX, +13

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16
Q

genetic mechanism of Turners and Klinefelters

A

nondisjunction during meiosis

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17
Q

features of Turners

A

X chromosome monosomy, webbed neck, short, cystic hygroma at birth (neck swelling), amenorrhea (no menstruation), gonadal dysgenesis, ‘streak ovaries’

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18
Q

what syndrome is associated with not having barr bodies

A

turners (45X) - no second X to have inactivated

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19
Q

features of Klinefelters

A

testicular atrophy, gynecomastia, female distribution of hair, infertile

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20
Q

chromosomal number of Klinefelters

A

47XXY

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21
Q

nondisjunction is most common in who and when

A

females during meoisis I

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22
Q

are the two maternal chromosomes from nondisjunction meiosis I identical

A

no - two different alleles

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23
Q

XXX female is a result of?

A

meiosis I and II nondisjunction in mom

meiosis II nondisjunction in dad

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24
Q

XYY fetus is a result of?

A

meiosis II nondisjunction in father

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25
Q

Klinefelters is a result of

A

47XXY
meiosis I and II nondisjunction in mom
meiosis II nondisjunction in dad

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26
Q

How do you differentiate between meiotic and mitotic nondisjunction?

A

mitotic nondisjunction is less severe

there will be areas of the body without trisomy or areas with different percentages of nondisjunction in mitotic nondisjunction

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27
Q

A newborn infant with a single palmar crease and depressed nasal bridge is suspected to have a genetic disorder. The karyotype analysis shows the presence of 100 cells of the karyotype 47,XX,+21. The most common mechanism that leads to this karyotypic abnormality is

A

nondisjunction during oogenesis

trisomy 21

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28
Q

difference between balanced and nonbalanced structural chromosomal abnormalities

A

balanced - there is no net gain or loss of genetic material

unbalanced - there is a net gain or loss of genetic material

29
Q

exchange of genetic material between non homologous chromosomes

A

reciprocal translocation

chromosomes are derivatives

30
Q

effect if reciprocal translocation occurs in somatic cells

A

possibly no change in phenotype (silent)

activation of oncogene —> cancer and can lead to increased growth rates of cells

31
Q

effect if reciprocal translocation occurs in germ line cells

A

higher incident of spontaneous abortion in the carrier

32
Q

difference between alternate and adjacent I and II segregation

A

alternate - balanced chromosomes

adjacent I and II - unbalanced chromosomes

33
Q

Philadelphia chromosome t(9;22) results in

A

activation of ABL proto-oncogene in hematopoietic cells —> chronic myelogenous leukemia

this occurs in somatic cells

34
Q

t(8;14) is number of what reciprocal translocation

A

Burkitt lymphoma (somatic cells)

35
Q

In a patient with chronic myelogenous leukemia, examination of the bone marrow cells reveal the presence of Philadelphia chromosome. This is a result of

A

balanced reciprocal translocation - exchange between two non homologous chromosomes

36
Q

Robertsonian Translocation happens between which chromosomes

A

acrocentric chromosomes 13, 14, 15, 21, 22

37
Q

what happens in robertsonian translocation

A

loss of short arm of two chromosomes involved (satellite contains genetic material for RNA)

fusion of the long arms of the two chromosomes involved

38
Q

karyotype of robertsonian translocation

A

45, XX, der (14;21) (q10; q10)

those last two sets of numbers will vary

39
Q

trisomy 14 is a type of

A

adjacent segregation - unbalanced genetic material

40
Q

causes of trisomy 21/ down syndrome

A 
robertsonian translocation (2-5%)
or nondisjunction during oogenesis
41
Q

karyotype of down syndrome as a result of robertsonian vs. nondisjunction

A

robertsonian - 46, XX, +21, der (14;21), (q10; q10)

nondisjunction - 47, XX, +21

42
Q

alternate segregation can result in…

A

normal gamete

or gamete with derivate chromosome that can result in robertsonian translocation carrier on fertilization

43
Q

adjacent segregation can result in..

A

trisomy of chromosome involved
for ex: trisomy 14 (not compatible with life) -> spontaneous abortion
trisomy 21 on fertilization

44
Q

A 25-year old female with a history of repeated
spontaneous abortions has a 2 year old girl withDown syndrome. Karyotype analysis of the mother reveals that she is a Robertsonian translocation carrier. What is the mechanism that produced Down syndrome in this child?

A

adjacent translocation during meiosis

45
Q

example of large deletion >4mb and what detects them

A 
Wolf Hirschhorn (4p-) and cri du chat (5p-)
detected by cytogenetic studies (light microscope)
46
Q

what detects small deletion <4Mb

A

high resolution prometaphase banding - FISH and array CGH

47
Q

does not detect balanced rearrangement

A

array CGH and SNP array

48
Q
  • Suspected deletion or duplication syndrome
  • Unexplained developmental delay or autism spectrum disorder
  • Congenital anomalies/dysmorphic features

all reasons for?

A

cytogenetic testing

49
Q

cri du chat is deletion of?

A

5p hence chromosome loses some of its genetic material

50
Q

features of cri du chat

A

high pitch cat cry, severe intellectual disability, speech problems microcephaly

51
Q

used to test for cri du chat

A

FISH and array CGH

52
Q

symptoms of DiGeorge’s syndrome aka 22q11 syndrome

A

CATCH 22

cardiac anomalies, abnormal facial features, thymic aplasia, cleft lip and palate, hypocalcemia

53
Q

increased risk of schizophrenia and most common contiguous gene

A

digeorges

54
Q

symptoms of Wolf Hirschhorn Syndrome

A

deletion of 4p, facial anomalies, widely spaced eyes, prominent nose, intellectual and developmental delay, abnormal iris, cardiac anomalies

55
Q

Wilms’ tumor, aniridia, genitourinary malformations, and retardation of growth and development

A

WAGR syndrome - small deletion

56
Q

uniparental disomy is a result of?

A

trisomy rescue

57
Q

what are inversions and what are the types

A

it is a flip of the chromosome
pericentric - flip around the centromere
paracentric - flip but does not involve centromere

58
Q

how are inversions identified

A

karyotype analysis

59
Q

results of inversion

A

usually balanced and no clinical problems in carrier

60
Q

risk to gamete of inversion carriers

A

during crossover, segments of chromosome are duplicated or deleted —>dicentric and acentric (not compatible with life - spontaneous abortions)

61
Q

is a deletion of a chromosome viable

A

no if an autosome

but is if it a sex chromosome

62
Q

what happens in isochromosome

A

there is a loss of one arm of chromosome and a duplication in the one that is still there

63
Q

isochromosome results in?

A

chromosomal and gene imbalance

64
Q

A child with Down syndrome has the genotype 1, 2, 3 for a polymorphism on chromosome 21 that has alleles 1, 2, 3, and 4. His mother is 1,2 and father is 3,4. Where did the nondisjunction occur?

A

maternal meiosis I nondisjunction

65
Q

when a chromosome loses genetic material at the terminal portions & the ends fuse to form a ring like structure

A

ring chromosome

66
Q

ring chromosome is seen in what type of people

A

radiation worker

67
Q

people often seen with X isochromosome

A

Turner Syndrome

68
Q

gives rise to phenotype of Turner

A

haploinsufficiency of genes on the petite arm that escaped X inactivation

69
Q

what happens to the isochromosome in Turner

A

it is typically inactivated

Genetics (19 decks)

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