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Flashcards in Inheritance patterns Deck (15):
1

Familial hypercholesterolaemia
Marfans syndrome
Adult polycystic kidneys
Huntington disease
Neurofibromatosis
Tuberous sclerosis
Myotonic dystrophy
Von WIllebrand disease
Osteogenesis imperfecta
Acute intermittent porphyria
Hereditary haemorrhagic telangiectasia
Noonan syndrome
Hereditary speherocytosis

Autosomal dominant

2

Penetrance

"Black or white"
AD
Genotype without any phenotype
"skipped generation"
Incomplete penetrance = some with mutation have disease, some don't
Eg. polydactyly

3

Expression

"Shades of grey"
AD
Same genotype, variable but always present phenotype
Variable expression = different manifestations
Eg. NF1

4

Mosaicism

More than one genotype in different cells
- point mutation or chromosomal abnormality
- germline vs somatic

5

De novo mutations

Common in AD and X-linked disorders
Rare in AR

More severe disorder = more common de novo mutations

6

Deafness (some)
Albinism
Wilson disease
Sickle cell disease
Thalassaemia
CF
Friedrich ataxia
Haemochromatosis
Phenylketonuria (PKU)
Alpha 1 anti-trypson deficiency
Homocystinuria

Autosomal recessive

7

2 in 3 rule

If a sibling of a person AFFECTED with a recessive syndrome is unaffected by the recessive condition, then they are either:
- heterozygote (carrier) 2/3
- wildtype homozygous 1/3

8

Incidence

1 / [ (Carrier frequency)2 x 4 ]

9

Carrier frequency

Square root of (Incidence / 4 )

10

Hardy Weinberg principle

Allele and genotype frequencies in the population will remain constant in the absence of other evolutionary influences

11

Haemophilia A
G6pd deficiency
Fairy disease
Ocular albinism
Testicular feminisation
Chronic granulomatous disease
Fragile X syndrome
Rett syndrome
Colour blindness
Duchenne muscular dystrophy
Hypophosphataemic rickets

X-linked

12

Angelman vs Prader Willi

Prader WIlli: absent Paternal allele expression
AngelMAN: absent MAternal allele expression

Loss of 15q12

13

Beck with Wideman vs Russel Silver

BW: loss of maternal 11p15 expression
BIG

RS: loss of paternal 11p15 expression
SMALL

Loss of 11p15

14

Mytonic dystrophy
Fragile X
Huntington disease
Some spinocerebellar ataxias

Triplet repeat disorder

15

Mitochondrial vs X-linked

No male-male

X-linked: males affected exclusively (or more severe than females)

Mitochondrial
- males and females affected to same extent
- no descendants of an affected male can have the disease (this CAN happen in X-linked)