Sex-linked Disorder and Mitochondrial Inheritance Flashcards
X linked disorders only usually affect males
Males are said to be …………….
hemizygous
-
-
More than one generation involved
Usually only males affected
No male to male transmission
Give some examples of X-linked recessive diseases
Duchenne/Becker muscular dystrophy
Red-green colourblindness
Fragile X syndrome
Haemophilia A and B
What is Gower’s sign a sign of? What is it?
Indicates muscular dystrophy
The way children stand up
Why is genetic counselling very important in X-linked recessive disorders?
All carrier females have a 25% risk or having affected sons
Why do some females show X-linked recessive traits? - - - -
- Skewed X-inactivation
- Turner’s syndrome
- Homozygous
- Chromosomal rearrangements involving the X chromosome and an autosome
What does a pedigree of X-linked dominant look like?
Give an example of a disease
Simliar to autosomal dominant
Excess of affected females
No male to male transmission
Vit D resistant rickets
What is sex influence?
When autosomal traits are expressed more frequently in one sex than another
Influence of sex through effect of male hormones
What is sex limitation?
Appearance of certain features in individuals of only one sex e.g. virilisation of female infants with congenital adrenal hyperplasia, an autosomal recessive disorder
What is the mitochondrial theory of ageing?
As age increases, number of mutant mitochondria increases
What are 3 key feature of mitochondrial inheritance?
What does this mean/
maternal inheritence
heteroplasmy: if a mutation arisis, it will create a mixed population of mitochondria within cell
expression threshold
Mitchondrial disease is said to be a multi system disease
What systems does it affect?
muscle weakness epilepsy deafness optic atrophy diabetes cardiomyopathy aplastic anaemia
What are three examples of mitochondral DNA disorders?
Kearns-Sayre syndrome - eye paralysis
MELAS - unusual strokes
MERRF - myclonic epilepsy with ragged red fibres
