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RCPsych Paper A > Genetics > Flashcards

Genetics Flashcards

1
Q

Mitosis stages

A

Prophase
Metaphase
Anaphase
Telophase

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2
Q

Prophase of mitosis

A

condensation of chromatic to discrete chromosomes
breakdown of nuclear envelope and formation of spindles at cellular poles

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3
Q

metaphase of mitosis

A

alignment of chromosomes at metaphase plate in middle - equatorial alignmnet

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4
Q

anaphase of mitosis

A

separation of paired chromosomes followed by migration to opposite ends of the cell
separation preserves the chromosomal umber in the daughter cells

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5
Q

telophase of mitosis

A

chromosomes are backed into distinct new nuclei in the emerging daughter cells
cytokinesis (division of cytoplasm) also starts at this time

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6
Q

mieosis

A

meiosis I and meiosis II
produces 4 daughter cells, either with half the number of parent chromosomes

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7
Q

how many chromosomes in human cell

A

46
(23 from each patent)

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8
Q

how many autosomes in human cell

A

22 pairs of autosomes
2 sex chromosomes

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9
Q

metacentric chromosome

A

centromere in the middle
p and q arms equal

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10
Q

acrocentric / submetcentric chromosome

A

p and q arms not equal
centromere closer to one end

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11
Q

telocentric chromosome

A

centromere at the tail of a chromosome
not seen in humans

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12
Q

holocentric chromosome

A

entire length of the chromosome acts as the centromere
not seen in humans

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13
Q

non-disjunction

A

failure of chromosome or chromatids to separate in meiosis, with one gamete receiving 2 copies of that chromosome and another with no copies

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14
Q

Down’s syndrome

A

Trisomy 21
1:700 births

reduced materal AFP, increased betaHCG, increased nuchal fold thickness on USS

95% due to meiotic non-disjunction
5% robertsonian translocation
1% mosaicism

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15
Q

Edwards syndrome

A

trisomy 18
severe mental retardation, rocker bottom feet, low set ears, micrognathia, congential heart disease, clenched hands, prominent occiput

1:8000
often death within 1 year of birth
F>M 3:1

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16
Q

Patau syndrome

A

Trisomy 13, 1:6000
severe mental retardation
microphthalmia
microcephaly
cleft lip/palate
coloboma eye
abnormal forebrain structures
polydactyly
congenital heart disease

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17
Q

Metafemale

A

trisomy X

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18
Q

Turners syndrome

A

80% from paternal X ch
1:2000 females
low hairline, broad chest, retronathism, webbed neck

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19
Q

Klinefelters

A

47 XXY

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20
Q

how many amino acids

A

20

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21
Q

how many possible codon combinations in genetic code

A

64

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22
Q

base pairs

A

AT
GC

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23
Q

DNA replication

A

production of new DNA copies from template DNA

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24
Q

Transcription

A

synthesis of RNA from nuclear DNA
takes place in cell nucleus

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25
Q

introns

A

junk sequences - do not code for anything

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26
Q

splicing

A

removal of introns
results in mRNA

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27
Q

translation

A

production of proteins from RNA
takes place in the cytoplasm
aided by ribosomes

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28
Q

exons

A

coding

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29
Q

point mutation

A

single base alteration in DNA
usually substitutions
could also be transition or transversion

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30
Q

frame shift mutations

A

deletion or insertion not in multiples of 3 codons
leads to shift in triplet reading frame with variable results

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31
Q

silent mutation

A

no change in protein product

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32
Q

mis-sense mutation

A

new mutant codon specifies a different AA with variable effects on final protein product

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33
Q

non-sense mutation

A

new codon is a stop codon
UUA UGA UAG
results in non functional protein

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34
Q

translocation

A

exchange of chunks of genetic materials from one chromosome to another
mutations occurring at ‘larger’ dimensions

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35
Q

reciprocal translocaiton

A

one segment exchanged for another segment among chromosomes

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36
Q

robertsonian transloation

A

non-reciprocal
results in single fused chromosome from 2 acrocentric non homologous chromosomes
small p arms are discarded, and metacentric fusion chromosomes results - single ch from the 2
only trivial loss of information
viable and ‘balanced’ within the individual

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37
Q

unbalanced translocation / monosomy

A

when gametes are formed, only one of the 2 gametes can have the whole translocated metacentric fusion chromosome

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38
Q

DiGeorge / velocardiofacial

A

22q11.2 autosomal dominant
deletion

mild-mod LD
facial deformities
cleft palate
malformed parathyroids - hypocalcaemia
broad nasal bridge
speech and swallowing problems
>25% have psychosis

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39
Q

Williams syndrome

A

7q11 microdeletion
hypercalcaemia at birth
supra valvular aortic stenosis
moderate LD
disinhibited disposition
speech artificially fluent
hyperacusis

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40
Q

Smith Magenis Syndrome

A

17p11.2 microdeletion
mod-severe LD
self harming behaviour
sleep disturbance
self hugging

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41
Q

angelman syndrome

A

15q11-13 deletion
maternally inherited

developmental delay, low IQ, jerky movement eg hand flapping
frequent smiling
seizures

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42
Q

prader willi syndrome

A

15q11-13 deletion
paternally inherited

obesity, short stature, small libs, decreased IQ, hyperphagia and skin picking

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43
Q

cri-du-chat syndrome

A

chromosome 5p deletion

feeding problems
cat like cry
poorly developed facial features

44
Q

mendelian laws of inheritance

A

uniformity
segregation
independent assortment

45
Q

law of uniformity

A

DD x dd = Dd
two alternative alleles at one locus
two homozygous parents
all offspring are of uniform type

46
Q

law of segregation

A

Dd x Dx = DD / Dd Dd / dd
two heterozygous parents
three possible types of offspring

47
Q

law of independent assortment

A

DdHh (blue eyes brown hair) x ddhh (brown eye, black hair) = DdHh / ddHh / Ddhh / ddhh

two loci with alleles D d H h
double heterozygote x double homozygote parent

4 possible types of offspring, each with equal probability

48
Q

incomplete penetrance

A

if patient have dominant disorder but does not manifest clinically
gives appearance of gene skipping a generation

49
Q

tuberous sclerosis

A

9q34 / 16p13
autosomal dominant
1:30,000

adenoma sebaceum, normal to severe MR, ash leaf macules, brain hamartomas, heart and kidney cysts

50
Q

treacher collins syndrome

A

5q31
autosomal dominant
1:40,000

maxilla mandibular hypoplasia
malformed pinna
down slanting palpebrae
mild to mod MR

51
Q

apert syndrome

A

10q
autosomal dominant

variable MR
cranio syntosis
shallow orbits
trapezoid mouth
mitten hands and feet

52
Q

noonan syndrome

A

Chr 12
autosomal dominant
1: 1500

mild MR
short stature
nuchal oedema/webbed neck
pulmonary stenosis
cryptorchidism

53
Q

hurler syndrome

A

4p16
autosomal recessive
1:100,000

deteriorating IQ after age 2
coarse facies
clouded cornea
joint stiffness

54
Q

lesch-nyhan syndrome

A

Xq 26-27
x linked recessive
deficiency of enzyme HGPRT

poor muscle control
moderate mental retardation
self mutilating behaviour - biting
hyperuricaemia
hyperuricosuria
severe gout and kidney problems

55
Q

mitochondrial inheritance

A

maternally inherited

MELAS
LHON (levers hereditary optic neuropathy)

56
Q

anticipation

A

disease develops earlier in successive generations

57
Q

fragile X syndrome trinucleotide repeat

A

CGG

58
Q

friedreich ataxia trinucleotide repeat

A

GAA

59
Q

huntington chorea trinucleotide repeat

A

CAGmyo

60
Q

tonic dystrophy trinucleotide repeat

A

CTG

61
Q

fragile X syndrome

A

males>female 2:1
trinucleotide repeat expansion CGG

anticipation seen

reduced IQ
enlarged testes
prominent ears
protracting jaw
high pitched voice

62
Q

southern blotting

A

detection of specific sequence of DNA

63
Q

western blotting

A

detection of specific protein after electrophoresis

64
Q

northern blotting

A

detection of specific RNA after electrophoresis

65
Q

PCR

A

minute amount of DNA can be amplified

between two oligonucleotide primers
denatured with heat then annealed

66
Q

FISH

A

detect and localise specific DNA sequences on chromosomes

isolated and inserted into plasmids which are vectors

67
Q

concordance

A

a twin pair is concordant when both co twins have the same disease expression

discordant if one has the disease and the other doesnt

68
Q

heritability

A

main measure of genetic variation in polygenic traits
the proportion that is genetic, not environmental
the relative influence of genetic factors in defining the variance in a trait

69
Q

schizophrenia heritability

A

80

69
Q

bipolar heritability

A

> 80

69
Q

major depression heritability

A

40

70
Q

generalised anxiety heritability

A

30

70
Q

panic disorder heritability

A

40

71
Q

phobia heritability

A

35

72
Q

alcohol dependence heritability

A

60

73
Q

big 4 personality traits in order of heritability

A

OECNA

openness - 57%
extraversion - 54%
conscientiousness - 49%
neuroticism - 48%
agreeableness - 42%

74
Q

hardy weinberg principle

A

in the absence of mutation, non-random mating, selection and genetic drift, the genetic constitution of the population remains the same from one generation to the next

75
Q

when does hardy weinberg equilibrium not hold true

A

natural selection
genetic drift
gene flow
consanguinity
high frequency of mutations

76
Q

genetic drift

A

gene frequency change caused by limitations in population size

77
Q

gene flow

A

exchange of genes between populations
due to migration or other social reasons, populations are not ‘closed’

78
Q

consanguinity

A

non-random mating occurs, and mutations are preserved within a closed pedigree
autosomal recessive diseases are more often seen in consanguinous families

79
Q

epistasis

A

gene-gene interactions between different alleles at different genes

80
Q

locus heterogeneity

A

when same diseases phenotype can be caused by mutations in different loci

81
Q

allelic heterogeneity

A

same disease phenotype resulting from different types of mutations at the same loci

82
Q

pleiotropy

A

when a single disease-causing mutation affects multiple organ systems

83
Q

monozygotic twins

A

identical twins
when embryo is cleared during early development

84
Q

dizygotic twins

A

fraternal twins
share 50% of genes
two ova two sperm

85
Q

pairwise concordance

A

number of twin pairs who both have the disorder divided by total number of pairs

86
Q

probandwise concordance

A

number of affected twins divided by total number of co-twins

87
Q

LOD score showing statistical evidence of linkage

A

> 3

88
Q

LOD as evidence that two loci not linked

A

-2 or less

89
Q

schizophrenia genes

A

NRG1
DTNBP1
G72
DAAO
RGS4
COMT
DISC1
dysbindin

90
Q

bipolar disorder genes

A

BDNF
DAO G72/G30
COMT

91
Q

alzheimers genetics

A

APP (Ch 21)
presenilin 1 (Ch 14)
presenilin 2 (Ch 1)
APOE

92
Q

CADASIL

A

form of amyloid angiopathy that can present with alzheimers like features

NOTCH3 is associated gene
19p13.1-13.2

93
Q

frontotemporal dementia genetics

A

progranulin gene (PGRN)
chromosome 17q21

94
Q

parkinsons disease genes

A

PARK1, PARK4 - 4q21 alpha synuclein
PARK2 6q25 parkin gene
PARK8 12 cen LRRK2 gene
PARK6 1p35-57 PINK1 mitochondria
PARK7 1p38 DJ-1

95
Q

autism sibling rate

A

2-8%
50x relative risk in siblings

96
Q

autism monozygotic concordance

A

60%

97
Q

autism dizygotic concordance

A

0%

98
Q

ADHD first degree relatives risk

A

15-60%
2-6 relative risk

99
Q

ADHD second degree relatives risk

A

3-9%
0.5-0.8 relative risk

100
Q

ADHD heritability

A

70-80%

101
Q

antisocial personality disorder heritability

A

60-70%

102
Q

panic disorder lifetime prevalence

A

4.7%

103
Q

approaches used in genetic clinics for genetic testing

A

direct testing - sample tested for certain genotype

gene tracking - many family members tested to see whether patient has inherited high risk Ch from heterozygous parent. can be used if the exact genetic locus associated with a disease is unknown

RCPsych Paper A (3 decks)

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