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WACS > GENETICS IN CLINICAL OBSTETRICS AND GYNAECOLOGY > Flashcards

GENETICS IN CLINICAL OBSTETRICS AND GYNAECOLOGY Flashcards

1
Q

Genomics

A
  1. preconceptional and prenatal testing
  2. Newborn screening
  3. Disease susceptibility
  4. Screening and diagnosis
  5. Prognosis and therapeutic decision
  6. Monitoring disease burden and recurrence
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2
Q

a stretch of nucleotides that code for a
polypeptide

A

gene

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3
Q

code for the protein that
the gene encodes

A

Exons

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4
Q

Codons

A
  1. Is genetic code
  2. made of RNA
  3. Consists of 3 sequential nucleotides
  4. Total possible number of codons is 64
    (because DNA contains 4 nucleotides)
  5. Is degenerate (ie. more than 1 codon
    can specify the same amino acid but no
    codon specifies more than 1 amino acid)
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5
Q

types of chromosomes

A

i. Metacentric (i.e. the 2 arms of the chromosome are equal in length)
il. Submetacentric
iii Acrocentric
iv. Telocentric (do not exist in humans)
v. Holocentric (do not exist in humans)

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6
Q

Largest chromosome

A

chromosome 1

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7
Q

Smallest chromosome

A

chromosome 22

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8
Q

Colchicine inhibits spindle formation. T/F

A

T

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9
Q

EDTA inhibits deoxyribonuclease. T/F

A

T

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10
Q

at metaphase, chromosome is identified by — stain

A

Giemsa stain

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11
Q

Genetic diseases can be categorized into
three major groups:

A
  1. chromosomal disorders
  2. single gene (monogenic) disorders
  3. multifactorial disorders
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12
Q

chromosomal abnormalities are subclassified into 2:

A
  1. numerical
  2. structural
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13
Q

numerical chromosomal abnormalities are - and -

A
  1. aneuploidy
  2. polyploidy
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14
Q

the six structural chromosomal abnormalitites are:

A
  1. translocation
    2 deletion
  2. insertion
  3. inversion
  4. rings
  5. isochromosome
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15
Q

*Aneuploidy refers to

A

an extra or missing chromosome, such as
–in trisomy 21 (Down syndrome) or
–monosomy 45XO (Turner syndrome)

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16
Q

Polyploidy refers to

A

numerical chromosome abnormalities in which
there is an addition of an entire complement of haploid chromosomes,
such as in
–triploidy, in which three haploid sets occur (69, XXX or XXY or XYY).
–Tetraploidy-4 haploid sets occuring

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17
Q

Numerical or aneuploid chromosome abnormalities involve either
autosomes or sex chromosomes. T/F

A

T

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18
Q

Most numerical chromosome abnormalities occur as the result of nondisjunction during meiosis or mitosis in which homologous chromosome pairs fail to disjoin. T/F

A

T

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19
Q

Nondisjunction occurs most commonly at meiosis 2. T/F

A

F. meiosis 1

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20
Q

there a strong correlation between increasing
maternal age and incidence of nondisjunction. T/F

A

T

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21
Q

Down syndrome has 3 copies of chromosome 21. T/F

A

T

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22
Q

——–% of down syndrome are caused by nondisjunction at gametogenesis

A

95%

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23
Q

—–% are mosaic for trisomy21

A

1–3%

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24
Q

—-% of individuals with clinical Down syndrome have a structural rearrangement (Robertsonian translocation)

A

2–4%

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25
Q

incidence of down syndrome

A

1:800

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26
Q

incidence of edward’s syndrome

A

1: 6000

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27
Q

incidence of Patau syndrome

A

1:15,000

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28
Q

incidence of turner syndrome

A

1:5000

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29
Q

incidence of klinefelter syndrome

A

!:1000

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30
Q

incidence of triple x syndrome

A

!:1000

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31
Q

incidence of xyy syndrome

A

1:1000

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32
Q

T/F: In human genetics only aberrations arising within germ cells are important

A

T

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33
Q

Examples of Diseases from deletions

A

*Cri-du-chat(5p-) syndrome
*DiGeorges Syndrome
*Wilms tomour
*Angelman and Prader-Willis yndrome

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34
Q

chromosome loses a segment because of breakage

A

deletion

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35
Q

rearrangements of the gene order within a single chromosome due to the incorrect repair of two
breaks

A

Inversion

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36
Q

centromere is outside inverted region

A

Paracentric inversion

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37
Q

centromere is within the inverted region

A

Pericentric inversion

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38
Q

the exchange of chromosomal material between two nonhomologous chromosomes

A

Translocation

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39
Q

2 types of translocation

A
  1. balanced reciprocal translocation
  2. robertsonian translocation
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40
Q

T/F: Balanced Reciprocal Translocations occur as a result of a mutual and physical exchange of chromosome (genetic) material between homologous chromosomes

A

F. non homologous chromosomes

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41
Q

T/F: Balanced Reciprocal Translocations cause no problem for mitosis

A

T

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42
Q

T/F: Balanced Reciprocal Translocations cause no problem for meiosis

A

F: may result in unequal distribution of chromosomes

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43
Q

incidence of balanced reciprocal translocations

A

1/11,000

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44
Q

T/F: The carrier of a reciprocal balanced translocation is usually phenotypically normal

A

T

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45
Q

T/F: balanced reciprocal translocation is associated with advanced paternal age

A

T

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46
Q

Involves any two acrocentric chromosomes that break near the
centromeres and re-join in a way that results in the long arms(q arms)
fusing at the centromere, forming a single chromosome structure and
loss of the short arms( p arm)

A

Robertsonian translocation

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47
Q

incidence of robertsonian translocation

A

1/9000 pregnancies

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48
Q

T/F: An individual with robertsonian translocation is genetically balanced, that is, he or she has two copies of each chromosome

A

T

49
Q

T/F: The gametes in robertsonian translocation are balanced

A

F.
the gametes are at risk to be unbalanced

50
Q

—-% of Down syndrome have Robertsonian translocation

A

5%

51
Q

major congenital abnormality in robertsonian translocation is seen in —%

A

4%

52
Q

T/F: numerical abnormalities are not inherited

A

T. Occur as random events during formation of reproductive cells

53
Q

T/F: some structural abnormalities are inherited

A

T. some also occur as random events during formation of reproductive cells or early fetal development

54
Q

T/F: single gene disorders or mendelian inheritance

A

T

55
Q

incidence of single gene disorders

A

3.6/1000 live births (2% of population)

56
Q

the probability that a gene will have any phenotypic expression at all

A

Penetrance

57
Q

the degree to which the phenotype is expressed

A

Expressivity

58
Q

Five basic modes of inheritance for Single-gene
diseases

A

–Autosomal dominant
–Autosomal recessive
–X-linked dominant
–X-linked recessive
–Mitochondria

59
Q

in autosomal dominant inheritance affected individuals have a ——-% chance of
transmitting the gene

A

50% (Inheritance =1:2)

60
Q

The gene product in autosomal dominant inheritance is commonly —-

A

non-enzymatic protein

61
Q

T/F: Autosomal Recessive inheritance is not typically seen in every generation
(NOT possible to trace via Family tree)

A

T

62
Q

T/F: females are more affected than males in autosomal recessive diseases

A

F. Males and female equally affected

63
Q

T/F: Consanguinity increases risk of offspring

A

T

64
Q

The gene product in autosomal recessive inheritance is commonly —–

A

an enzyme

65
Q

T/F: incidence of X-linked recessive disorders is seen only in males

A

F. much higher in males than females

66
Q

T/F: there’s no father to son transmission in xlinked recessive disorders

A

T

67
Q

—-% of daughters of affected males are carriers

A

100%

68
Q

what is the % of inheritance in son and daughters of carrier females

A

50% of sons infected and 50% of daughters carriers

69
Q

X-linked dominant disorders are seen in only females

A

F.
males and females affected but females more severely affected

70
Q

for an affected male in X-linked dominant inheritance, what is the incident of transmission to his sons and daughters?

A

no male to male transmission
all daughters affected

71
Q

in X-linked dominant disorders, for an affected female what is the incidence of transmission to sons and daughters

A

1 in 2 risk to children (M+F)

72
Q

T/F: In mitochondrial inheritance it is difficult to determine the risk of transmission to offspring

A

T

73
Q

T/F: All genes in multifactorial diseases work in the context of environment and behavior

A

T

74
Q

T/F: Only single disorders follow a clearly defined pedigree pattern of inheritance “Mendelian Pattern”.

A

T

75
Q

T/F: In Mendelian Inheritance, for several diseases the family tree may be conclusive even if accurate diagnosis is not made

A

T

76
Q

Essential Components of Genetic Counselling

A
  1. History and pedigree construction
  2. Clinical Examination
  3. Confirmatory diagnosis
  4. Calculation of recurrence risk
  5. Counselling
  6. Follow-up
77
Q

ETHICAL PRINCIPLES

A
  1. Beneficence
  2. Autonomy
  3. Justice
  4. Non-Maleficence
  5. Veracity
  6. Fidelity
78
Q

maternal serum screening for prenatal diagnosis

A

fetoprotein, estriol and hcg estimation

79
Q

amniocentesis for prenatal diagnosis

A

fetoprotein, acetylcholinesterase, chromosomal analysis, biochemical analysis

80
Q

CVS for prenatal diagnosis

A

chromosomal analysis, biochemical analysis, DNA analysis

81
Q

Fetal blood sampling for prenatal diagnosis

A

chromosomal analysis, DNA analysis

82
Q

Invasive methods of prenatal diagnosis

A
  1. coelocentesis
  2. CVS
  3. Amniocentesis
  4. cordocentesis
  5. biopsy from fetal tissue
83
Q

Non invasive methos of prenatal diagnosis

A
  1. cell free fetal DNA
  2. triple test
  3. USS
  4. MRI
84
Q

amniocentesis is performed in which trimester

A

2nd

85
Q

incidence of miscarriage with amniocentesis

A

1 in 300 - 500

86
Q

CVS is done in which trimester

A

2nd

87
Q

risk of miscarriage with CVS

A

1 in 300 -500

88
Q

cordocentesis is also called

A

PUBS

89
Q

when can cordocentesis be done

A

after 18 weeks

90
Q

what is the risk of miscarriage with cordocentesis

A

2 in 100 women will miscarry

91
Q

at what GA should fetal tissue biopsy be done

A

17 - 20 weeks

92
Q

T/F: < 1 in 1000 women will get infection with fetal tissue biopsy

A

T

93
Q

at what GA should coelocentesis be done

A

before 10 weeks

94
Q

the space between the amniotic cavity and uterine cavity

A

coelomic space

95
Q

incidence of fetal loss with coelocentesis

A

0 or < seen in amniocentesis

96
Q

fetal fraction in maternal blood for cell-free fetal DNA

A

> 3.5%

97
Q

T/F: cell-free fetal DNA is affected by gestational age and maternal BMI

A

T

98
Q

T/F: High false positive rates with cell-free fetal DNA

A

F. low

99
Q

reason for false positives seen with cell-free fetal DNA testing

A

results confounded by placental mosaicism, chromosomal translocations, uniparental disomy, vanishing twin

100
Q

T/F: cell-free fetal DNA can detect trisomies 18, 13 and 21

A

T

101
Q

triple test meases –,— and –

A

alpha fetoprotein, hcg and unconjugated estriol

102
Q

quadruple test measures –,–,– and –

A

alpha fetoprotein, hcg, unconjugated estriol and inhibin A

103
Q

T/F: adequate DNA is obtained with one process of PCR examination

A

F.
Repeat process 30 times to get adequate DNA

104
Q

T/F: PCR identify specific DNA sequence for gene mutation & prenatal Dx.
at an earlier stage before an embryo transfer in IVF cycle.

A

T

105
Q

FISH detects specific DNA sequences in – and– phases of the cell cycle

A

interphase and metaphase.

106
Q

T/F: FISH results are available in one week

A

F. 24-48hrs

107
Q

T/F: FISH allows detection of big structural rearrangements

A

F.

108
Q

FISH Identifies —% clinically relevant abnormalities

A

80%

109
Q

read the order of bases (ATGC) in genome of an individual

A

sequencing

110
Q

first generation sequencing

A

sanger sequencing: single gene disorders, 300-1000bp, cost implication

111
Q

second generation sequencing

A
  1. pyrosequencing:
  2. ion torrent
  3. illumina sequencing
112
Q

3rd generation sequencing

A

pacific biosciences: single molecule real time sequencing, epigenetic studies

113
Q

4th generation sequencing

A

nanopore technology

114
Q

ADVANTAGES OF next generation sequencing

A
  1. targeted gene sequencing
  2. whole genome sequencing: entire nucleotide sequence of the genome
  3. whole exome/clinical exome sequencing: protein coding regions
115
Q

examples of multifactorial diseases

A

Spina bifida, diabetes, and heart disease

116
Q

examples of X linked dominant diseases

A

FAIR:
F - (oro) facial syndrome
A - alports
I - incontinenta pigmento
R - resistant rickes (hypophosphatemic)
R - Rett syndrome

117
Q

examples of X-linked recessive diseases

A

(Be Wise, Fools GOLD Heeds Silly Hope)

B - Bruton’s agammaglobulinaemia
W - Wilscot aldrich syndrome
F - Fabry’s syndrome
G - G6PD deficiency
O - ocular albinism
L- lesch nyhan syndrome
D - dystrophy (duchenne’s and beckers)
H - hunter’s syndrome
H - haemophilia A and B

118
Q

examples of autosomal recessive diseases

A

PASTA CHAWAL

P - phenylketonuria
A - alkaptonuria
S - sickle cell anaemia
Ta - thalasemia
C - cystic fibrosis
H - haemochromatosis
A - alpha AT deficiency
W - wilson disease
A- albinism, adrenal hyperplasia
L - lysosomal and glycogen storage disease

119
Q

examples of autosomal dominant diseases

A

Very Powerful DOMINANT Humans

V - von willebrand and von hippel lindau
P - pseudohypoparathyroidism
D - dystrophia myotonica
O - osteogenesis imperfecta and osler weber rendu
M - marfan syndrome
I - intermittent porphyria
N - neurofibromatosis
A - achondroplasia and adult polycystic kidney disease
N - noonan syndrome
T - tuberous sclerosis
H - hypercholesterolaemia, huntington disease, hypertrophic obstructive cardiomyopathy, hereditary spherocytosis, hereditary non polyposis colon ca, hereditary haemorrhagic telangiectasia

WACS (19 decks)

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