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clinical genetics Flashcards

1
Q

what are multifactorial genetic disorders?

A

disorders affecred by environmental and genetic factors

one organ system affected

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2
Q

what are single gene genetic disorders?

A

mutation in a single gene which affect protein in the body

dominant/recessive patterns

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3
Q

what are chromosomal genetic disorders?

A

thousands of genes involved
multiple organ systems affected
trisomes, deletions and duplications - translocations are inherited

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4
Q

what are mitochondrial genetic disordes?

A

genetic disorders in the mitochondria - inherited from the mother

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5
Q

what are somatic genetic disorders?

A

cancer

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6
Q

what is penetrance?

A

the frequency with which the characteristic controlled by a gene is seen in individuals possessing it

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7
Q

what is expressivity?

A

differing clinical features/ phenotype among those with the same alleles/ genotype

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8
Q

give an example of a mitchondrial disorder

A

leber hereditary optic neuropathy

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9
Q

when does crossing over occur?

A

meiosis II

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10
Q

what is the structure of a chromosome?

A

long continuous piece of DNA with genes in linear order
chromosomes also contain RNA, histone protiens and non-histone proteins as packaging
during metaphase, chromosomes become highly condensed

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11
Q

how do chromosome abnormalities cause issues?

A

they alter the amount of products of genes invovled

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12
Q

what are numerical chromosome abnormalities?

A

change in number of chromosomes
aneuploidy - different number of a particular chromosome in a cell - monosomy, trisomy
polyploidy - having more that 2 paired sets of chromosomes - triploidy

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13
Q

what are structural chromsome abnormailites?

A

translocations - reciprocal (exchange between 2 chromsomes) or robertsonian (part of chromsome on another)
deletions
duplications
inversions

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14
Q

what are different cell line chromosome abnormalities

A

2 or more genetically different cells in the body

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15
Q

what are most chromosome abnormalities caused by?

A

de novo events in meiosis

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16
Q

why do new mutations increase with paternal age?

A

due to greater number of germ cell divisions

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17
Q

what is mosaicism?

A

after fertilisation embryo undergoes abnormal separation of chromsomes in one of its cells in mitosis = mitotic non-disjunction
results in fetus with 2 or more populations of cells.

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18
Q

give an example of mosaicism?`

A

down syndrome

2 population of cells - 45XY-21 and 47XY+21

19
Q

What is gametogenesis?

A

process by which cells undergo meiosis to form gametes

20
Q

what is non-disjunction?

A

failure of homologous chromosomes to separate properly during cell division

21
Q

what is centric fusion/robertsonian

A

breakage of 2 acrocentric chromosomes at or close to centromeres with subsiquent fusion

22
Q

what are the symptoms of down syndrome?

A 
clinical features:
round face
protruding tongue
upslanting palpebral fissures
epicanthic folds 
developmental delay
23
Q

what is the cause of down syndrom?

A

trisomy 21 karyotype

24
Q

what is karyoping?

A

determination of the karyotype to detect chromosomal abnormalities

25
Q

what is the normal chromosomal karyotype?

A

46,XY or 46,XX

26
Q

What is flourescence in situ hybridization? (FISH)

A

production of FISH probes for olfactory homolgues with flourescent markers
apply to chromsome that has been denatured and floursecence occurs at ;points

27
Q

what is FISH used for?

A

to detect specific DNA sequecnes in interphase nuclei or chromsomes - such as willams-beuren syndrome

28
Q

name 3 autosomal trisomies

A

down sydrome
edwards syndrome
patau syndrome

29
Q

what is edwards syndrome?

A

autosomal trisomy 18
multiple malformations - of heart and kidney inparticular
clenched hands with overlapping fingers

30
Q

what is patau syndrome?

A

trisomy 13
multiple malformations
affects midline structures - incomplete lobation of the brain, cleft lip, congenital heart disease

31
Q

what are anomalies of sex chromosome number caused by?

A

abnormal gametes with unusual complements of sex chromsomes

32
Q

what is the karyotype of kinefelter syndrome and its symptoms?

A 
47,XXY
infertility
poorly developed sexual characteristics
gynaecomastia (males get boobs) and osteoporosis (weak bones)
tall
33
Q

what is the karyotype and symptoms of turner syndrom?

A

45,X
short stature, wide carrying angle of arms
primary amenorrhoea
congenital heart disease

34
Q

what are microdeletions?

A

chromosomal regions that are lost , too small to be observed microscopically, identified by use of specific moleuclar cytogenetic techniques

35
Q

2 example sof microdeletions?

A

DiGeorge syndrome

williams-beuren syndrome

36
Q

what are the typical facial features of DiGeorge syndrome?

A

small muth, prominant nose

37
Q

what are the typical facial feature sof williams-beuren syndrome?

A

bright eyes, wide mouth, upturned nose, long philtrum, flattened nasal bridge

overly sociable

38
Q

give 4 examples of single gene disorders

A

huntingtons disease
familial hypercholesterolaemia
cystic fibrosis
duchenes muscular dystrophy

39
Q

what are some symptoms of huntigntons disease

A 
irritability
depression
involuntary movements
poor coordination
trouble learning new infromation
trouble making decisions
40
Q

what is the cause of huntingtons disease?

A

altered HTT gene - the CAG repeat increases in size

41
Q

what is familial cholesterolaemia?

A

disorder if cholesterol metabolism
causing premature atherosclerosis and cardiovascualr disease

autosomal dominant mutation in LDLR - encodes LDL cholesterol receptor

42
Q

signs of familial cholesterolaemia?

A

high LDL

cholesterol deposits such as arcus cornealis

43
Q

what is cystic fibrosis?

A

autosomal recessive condition of defective CF gene

affects secretory glands including mucus and sweat glands

44
Q

what is duchenne muscular dystrophy

A

mutation in DMD gene which produces dystrophin
absence of dystrophin cuases disorganisation of muscle and invasion by fibrous tissue
=weak proximal muscles

IMS (14 decks)

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