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Flashcards in Clinical genetics Deck (46):
1

the aetiology of disease rests on 3 conditions

100% environmental
Single gene
polygenic

2

deine multifactorial disorder

multiple genes (genetic predisposition) and environmental factor

3

define single gene disorder

a mutation in a single gene = Mendelian inheritance

4

define chromosomal disorder

an imbalance or rearrangement in chromosome structure eg aneuploidy, deletion, translocation

5

define mitochondrial

a mutation in mitochondrial DNA

6

define somatic mutation

mutation(s) within a gene(s) in a defined population of cells that results in disease

7

what are the 4 gene modes of inheritance

autosomal dominant
autosomal recessive
X-linked
Mitochondrial

8

how many chromosomes do we have

46 chromosomes.

9

do autosomal dominant conditions run from generation to generation.

Yes.

10

Are males and females equally affected in autosomal dominant conditions

Yes.

11

what % does offspring of an affected person have of inheriting the condition

50%

12

what types of molecules do mutations of a autosomal dominate fashion affect.

structural proteins, receptors and transcriptional factors.

13

examples of conditions which are inherited in a autosomal dominant manner

myotonic dystrophy
marfans syndrome
Huntingtons disease

14

define penetrance

Frequency of people with the genotype who express certain charcterisitics.

15

define full penetrance

mutation results in have the disease.

16

define incomplete penetrance

mutation is present but they may not have the disease.

17

define expressivity

variation in expression ( the extent to which a heritable trait is manifested by an individual)

18

define anticipation

symptoms more apparent at an earlier age as it is passed from one generation to the next.

19

define de novo mutations

new mutation that has occurred during gametogenesis or in early embryonic development.

20

Do autosomal recessive conditions pass from generation to generation

No- parents typically affected .

21

what types of relationship increase risk of recessive disorders.

consanguineous

22

do autosomal recessive conditions affect males and females equally

Yes.

23

what % chance will the offspring of an affected person will get the condition

25%

24

what % chance is there that a affected person will have a offspring who is a carrier

2/3
66%

25

examples of autosomal recessive conditions

cystic fibrosis
metabolic disorders
sickle cells disease
Haemachromatosis.

26

which gender is affected in X-linked conditions

males.
(females can be mildly affected0

27

Can you have ale to male transmission of a X-linked condition

No.

28

examples of X-linked conditions

duchenne's muscle dystrophy
fragile X syndrome
Red/green colur blindness
Haemophillia

29

if the mother is a carrier of a X-linked condition then what are the chances that the male is affected.

25%

30

If the mother is a carrier of a X-linked condition then what are the chances that the female is carrier

25%

31

If the father is affected by a X-linked condition then how will this affect all daughter and son offspring

all daughters are carriers.
all sons are unaffected.

32

what are the 2 main factors which cause females to have such variable X-linked phenotypes

X inactivation
XL dominant vs XL recessive inheritance inheritance

33

X inactivation is aka

Lyonisation

34

what happens in X-inactivation

The process of random inactivation of one of the X chromosomes in cells with more than one X chromosome.
Compensates for the presence of the double X gene dose.

35

what is the shut down X in lyonisation called

Barr body.

36

when does X inactivation take place

early embryogenesis.

37

define skewed X-inactiavtion

random preference for “normal” X chromosome to be inactivated

38

define tissue variability (int terms of X inactivation)

random preference for the X chromosome with the mutation to be active in crucial tissue group

39

define X linked dominance

a dominant gene is only carried on the X chromosome (less common than recessive condition)

40

define X linked recessive

a recessive gene is only found on the X chromosome ( more common that dominant condition)

41

example of XL dominant

Rett syndrome
Fragile X syndrome

42

examples of XL recessive

Red-green colour blindness
Haemophilia
Duchene Muscular dystrophy

43

is mitochondrial inheritance from the mother father or both.

All our mitochondria are inherited from our mother

44

how many genes have mitochondrial DNA

27

45

How will the children of a affected mother be affected

all have mutation

46

How will the children of a affected man be affected

not affected.