genetics physio Flashcards

1
Q

single gene dos

A

heritable
often due to spontaneous mutation at first
5 main patterns:
auto dom/rec
x linked dom /rec
y linked

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2
Q

how to determine inheritance pattern

A

pedigree diagram

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3
Q

how to determine recurrence risk

A

monohybrid cross amd punnet square

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4
Q

AD inheritance characteristics

A

affects both genders
tranmission one gen to next
all forms of trans (m-m, m-f etc)
normal + affect have 50% chance of affected offspring

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5
Q

ad conditions

A

marfans syndrome - long boi
achondroplasia - dwarf
neurofibromatosis type 1 - axillary or groin freckles, adult clusters of fibromas, false joint
myotonic dystrophy - long face, gynaecomastia

postaxial polydactyly- extra lil fingie
familial hyperchol
huntingtons dx

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6
Q

AR characteristics

A

m and f affected
recessive traits only manifest in homozyg
heterozyg are unaffected and carriers
offspring of 2 heterozyg is 25% chsnce of affected

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7
Q

ar dos

A

occulocutaneous albinism
sickle cell dx
cystic fibrosis
spinal musclar atrophy

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8
Q

xlr characteristics

A

affected father - all f will be carriers
affected mother - all offspring either affected or carriers
carrier mother - half daughters carriers, half sons affected, rest normal
mainly males affected
affected m will not have affected m offspring

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9
Q

xlr dos

A

duchennes muscular dystrophy - normal till age 6 and quickly degen
hemophilia
r g colour blindness

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10
Q

xld characteristics

A

father affected - all f affected and m unaffected
mother affected - 50/50 for all

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11
Q

non mendelian inheritance

A

mitochondrial inheritance
maternal lineage transmission

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12
Q

xld dos

A

fragile x syndrome - mental retardation in males
x linked hypoposphataemia (rickets)

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13
Q

y linked characteristics

A

always affected m has affected m offspring
very few genes and so rare dos

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14
Q

y genes carries

A

sry gene - absent results in ambiguous genitalia
spermatogenesis genes
H-Y histocompatibility Ag (transplant)

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15
Q

what has lower recurrence risk uni or multifactorial dos

A

multifactorial

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16
Q

what creates the highest relative risk

A

high risk genotype + high risk environment

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17
Q

common multifactorial dos

A

cleft lip
cdh
chd
neural tube defects
pyloric stenosis
congential talipes equinovarus - club foot

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18
Q

variance of multifactorial dos

A

does not fit in with mebdelian patterns
clusters in family may be genetically predisposed but
environment plays a significant role in the phenotype in the individual

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19
Q

neural tube defects (ntd)

A

high recurrence risk - 60%
number of siblings affected correlates to increased risk of subsequent affected offspring

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20
Q

cleft lip with or w/o cleft palate

A

76% heritability
syndromic vs non syndromic
uni/bilat

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21
Q

ctev - club foot

A

congential talipes equinus varus
68% heritability
often a result of the environment

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22
Q

chd

A

35% heritability
acyanotic vs cyanotic chd
trisomies - downs - avsd
teratogens - congen infections

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23
Q

common defect in acchd

A

vsd

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24
Q

common defect in cchd

A

tetralogy of falot

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25
Q

cancer can be due to

A

inherited mutations: tumour suppressor genes / proto oncogenes

somatic cell mutations: not inherited, accumulation of mutations

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26
Q

brca1 & 2

A

carry > 75% risk
f - ovarian, m - prostate
auto dom

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27
Q

fap

A

mutation of apc gene
early onset of colon carcinoma

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28
Q

lynch synd / hnpcc

A

familial cases of cancers in different organs

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29
Q

genetic syndromes linked to cancer

A

downs - leukemias
albinism - skin cancer
nf1 & 2 - neurofibromas
etc

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30
Q

obesity

A

6-85% heritability
heavily influenced by environment

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31
Q

dbt mel t1

A

must be triggered
higher rel risk
environmental factors - diet, viral exposure in childhood

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32
Q

dbt mel t2

A

primarily due to lifestyle
no major genetic cause but are susceptibility genes
environmental factors - age, sedentary, metabolic syndrome

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33
Q

chromosomal abnormality

A

morphological or numerical alteration in single or multiple chromosomes, may affect autosomes or sex chromosomes

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34
Q

what proportion of common cancers have strong hereditary component

A

5-10%

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35
Q

what proportion of neonates have at least one major congen abn

A

3%
50% of which are exclusively or partially genetic factors

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36
Q

what is proportion of children who show developmental problems

A

12-14%

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37
Q

what proportion of older adults in developed countries have genetic medial problem

A

50%

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38
Q

different types of chromosomal abn

A

numerical
structural
different cell lines (mixoploidy)

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39
Q

aneuploidy types

A

mono
tri
tetrasomy

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40
Q

polyploidy types

A

triplo
tetraploidy

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41
Q

types of numerical abn

A

aneuploidy and polyploidy

42
Q

types of structural abn

A

translocation - reciprocal vs robertsonian
deletions
insertions
inversions - paracentric vs pericentric
rings
isochromosomes

43
Q

types of mixoploidy

A

mosaicism
chimerism

44
Q

implication of germline mutation

A

that mutation is incorporated in every cell of the body and can be heritable vs somatic mutation which is acquired in a single body cell

45
Q

genetic chimerism

A

single organism composed of cells from different zygotes
m + f organs
two blood types
merging of two fertilized eggs

46
Q

mosaicism

A

state of being composed of cells of two genetically different types in a single organism developed from a single zygote

47
Q

chimerism vs mosaicism

A

c - different germ lines and zygotes
m - different germ lines SAME zygote

48
Q

euploid defn

A

n number of chroms (2n)

49
Q

polyploidy defn

A

chrom number is exact multiple of haploid number (n) eg 2n, 3n, 4n
triplo/tetraploidy

50
Q

aneuploidy defn

A

chrom number not exact multiple
trisomy - over diploid n
monosomy - one chrom missing

51
Q

karyotype of triploidy

A

69, XXY

52
Q

karyotype of trisom 21

A

47, XX + 21

53
Q

karyotype of klinefelters synd

A

47, XXY

54
Q

karyotype of turners synd

A

45, X

55
Q

balanced translocations

A

extra gene is moved somewhere else

56
Q

structural abn can result from (breakage process)

A

chrom breakage
sticky ends produced
repair mechanisms join these ends
soemtimes the wrong ends are joined
breakage increases by ionic exposure and mutagens

57
Q

translocation definition

A

transfer of chom material between chroms
balanced does not pose a problem

58
Q

types of translocations

A

reciprocal
central fusion - eg Robertsonian - rel to ds
insertional

59
Q

deletion

A

loss of any part of chrom

60
Q

duplication

A

presence of two copies of segment of chrom. less harmful than deletion

61
Q

inversion

A

180° change in direction of chrom seg

62
Q

ischrom

A

abn chrom where deletion of one area
and dup of another area

63
Q

centric fragment

A

addition of small fragment, usually metacentric

64
Q

robertsonian transloc

A

breakage of two acrocentric chroms at or near the centromere

65
Q

reciprocal transloc

A

exchange of gen material away from centromere

66
Q

balanced transloc

A

no overall loss or gain
carriers often unaffected

67
Q

unbalanced trans

A

feotus may spontaneously abort
liveborn may have dysmorphic features etc

68
Q

transloc of ds

A

robertsonian trans when chr 21 joins with 14

69
Q

pericentric inversions

A

include centromere

70
Q

paracentric inversion

A

does not include centromere

71
Q

ring chrom

A

when breaks occurs on each arm of chrom leaving 2 sticky ends
portions unite to form a ring

72
Q

isochrom

A

when a chrom loses one of its arms and replaces with an exact copy of the other arm
replicated and symmetrical across centromere

73
Q

brushfields spots

A

speckled iris, little white spots slightly elevated on the surface

74
Q

klinefelters synd

A

47, XXY
1 in 1000 male live births
child- mild learning difficulties iq red
adult- taller with longer limbs, gynaecomastia, absence of sperm, leg ulcers

75
Q

turners synd

A

45, X
1 in 5000 to 10000
2nd trim - swelling at back of neck
birth and childhood normal
short stature with ovarian failure
absence of menstruation
infertile

76
Q

47, XYY

A

non disjunction at paternal meiosis 2 or as post zygotic event

77
Q

fragile x synd

A

1 in 5000 males accounts for 4-8% of males with learning difficulties
fragile side close to telomere at end of long arm

78
Q

angelman and prader willi synd

A

microdeletion in the chrom 15
maternal- a synd
paternal- pd synd

79
Q

angelman synd clinical

A

inapprop laughter, convulsions, poor coord

80
Q

parder willi synd clinical

A

hupotonic, poor infancy feeding, developes into hyperphagia and obesity

81
Q

teratogens defn

A

agents that interfere with cell growth, differentiation, proliferation, migration, causing structural/ functional abn flowing pregnancy
each has a specific pattern of effects

82
Q

highest incidence of teratogenic

A

fetal alc spectrum do

83
Q

teratogen exposure pre-implantation

A

does not result in congen abn

84
Q

teratogen exposure during embryonic phase

A

wk 3-8
highest risk for damage

85
Q

teratogen exposure during feotal period

A

less susceptible
organ systems grow and mature

86
Q

high risk of teratogenicity

A

wks 3-8

87
Q

direct teratogen

A

by passes the placental barrier to affect feotus

88
Q

indirect teratogen

A

affects mothers metabolism / circulation eg alcohol

89
Q

effects of tobacco

A

low bw
premie
resp complications
chd
fetal /infant death

90
Q

dna methylation

A

prevents transcription on a certain gene to silence growth

91
Q

histone modification

A

histone prevent dna from tangling and protects from damage
it can be modified by enzymes to partially unwind making it more accessible for expression

92
Q

no coding rna

A

rna produce protein
ncrnas called enhancer rnas transcribe from enhanced region of a gene promote the gene expression

93
Q

epigenetics

A

the study of the signals than control or order dna to do stuff

94
Q

criteria for screening program

A

the disease - common and have serious defects that are preventable
the test - accurate and reliable + high spec and sens
the program - fair and equitable, voluntary and reasonable and affordable

95
Q

types of tests

A

carrier tests - for recessive genes
presymptomatic- auto dom eg huntingtons
inherited predisp - brca
prenatal - ds
newborn - sickle cell
identity - paternity
physical exam

96
Q

proportion of genic causes for congent defects

A

30-45%

97
Q

syndrome defn

A

consistent and recognizable pattern of abn fot which there is a known underlying causes
or
>3 dysmorphic features

98
Q

sequence defn

A

several findings occurring consequently
to a cascade of events
initiated by single prim factor
eg potter seq

99
Q

association defn

A

non random occurrence of certain malforms
more often than would be expected by chance
eg vacterl association

100
Q

malformations

A