Clinical genetics

Question 1

the aetiology of disease rests on 3 conditions

Answer 1

100% environmental
Single gene
polygenic

Question 2

deine multifactorial disorder

Answer 2

multiple genes (genetic predisposition) and environmental factor

Question 3

define single gene disorder

Answer 3

a mutation in a single gene = Mendelian inheritance

Question 4

define chromosomal disorder

Answer 4

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

Question 5

define mitochondrial

Answer 5

a mutation in mitochondrial DNA

Question 6

define somatic mutation

Answer 6

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

Question 7

what are the 4 gene modes of inheritance

Answer 7

autosomal dominant
autosomal recessive
X-linked
Mitochondrial

Question 8

how many chromosomes do we have

Answer 8

46 chromosomes.

Question 9

do autosomal dominant conditions run from generation to generation.

Answer 9

Yes.

Question 10

Are males and females equally affected in autosomal dominant conditions

Answer 10

Yes.

Question 11

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

Answer 11

50%

Question 12

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

Answer 12

structural proteins, receptors and transcriptional factors.

Question 13

examples of conditions which are inherited in a autosomal dominant manner

Answer 13

myotonic dystrophy
marfans syndrome
Huntingtons disease

Question 14

define penetrance

Answer 14

Frequency of people with the genotype who express certain charcterisitics.

Question 15

define full penetrance

Answer 15

mutation results in have the disease.

Question 16

define incomplete penetrance

Answer 16

mutation is present but they may not have the disease.

Question 17

define expressivity

Answer 17

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

Question 18

define anticipation

Answer 18

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

Question 19

define de novo mutations

Answer 19

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

Question 20

Do autosomal recessive conditions pass from generation to generation

Answer 20

No- parents typically affected .

Question 21

what types of relationship increase risk of recessive disorders.

Answer 21

consanguineous

Question 22

do autosomal recessive conditions affect males and females equally

Answer 22

Yes.

Question 23

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

Answer 23

25%

Question 24

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

Answer 24

2/3

66%

Question 25

examples of autosomal recessive conditions

Answer 25

cystic fibrosis
metabolic disorders
sickle cells disease
Haemachromatosis.

Question 26

which gender is affected in X-linked conditions

Answer 26

males.

(females can be mildly affected0

Question 27

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

Answer 27

No.

Question 28

examples of X-linked conditions

Answer 28

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

Question 29

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

Answer 29

25%

Question 30

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

Answer 30

25%

Question 31

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

Answer 31

all daughters are carriers.

all sons are unaffected.

Question 32

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

Answer 32

X inactivation

XL dominant vs XL recessive inheritance inheritance

Question 33

X inactivation is aka

Answer 33

Lyonisation

Question 34

what happens in X-inactivation

Answer 34

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.

Question 35

what is the shut down X in lyonisation called

Answer 35

Barr body.

Question 36

when does X inactivation take place

Answer 36

early embryogenesis.

Question 37

define skewed X-inactiavtion

Answer 37

random preference for “normal” X chromosome to be inactivated

Question 38

define tissue variability (int terms of X inactivation)

Answer 38

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

Question 39

define X linked dominance

Answer 39

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

Question 40

define X linked recessive

Answer 40

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

Question 41

example of XL dominant

Answer 41

Rett syndrome

Fragile X syndrome

Question 42

examples of XL recessive

Answer 42

Red-green colour blindness
Haemophilia
Duchene Muscular dystrophy

Question 43

is mitochondrial inheritance from the mother father or both.

Answer 43

All our mitochondria are inherited from our mother

Question 44

how many genes have mitochondrial DNA

Answer 44

27

Question 45

How will the children of a affected mother be affected

Answer 45

all have mutation

Question 46

How will the children of a affected man be affected

Answer 46

not affected.