Modes of inheritance

Question 1

What factors cause variability in presentation for mitochondrial disease?

Answer 1

Number of affected mitochondria-Going over threshold

Age-Number of mitochondria accumulates

Cells with different number of mutated mitochondria

Question 2

Why do some mitochondria not exist with a disorder when they contain the mutation in copies of their genome?

Answer 2

Mitochondria contain many copies of their genome, some mutant and some normal.

-There is a threshold the mitochondria must be above to exhibit characteristics of the disease

Question 2

What mode of inheritance may affect all children if their mother is affected?

Answer 2

Mitochondrial inherited disorder

Question 3

Most likely cause of mitochondrial disease?

Answer 3

Mutation in mtDNA

Question 4

Answer 4

Y-linked disorder

Question 5

What type of inheritance affects only males no matter the scenario?

Answer 5

Y-linked disorders

Question 6

Answer 6

X-linked dominant

Question 7

What mode of inheritance constitutes that no sons and all daughters of an affected father are affected?

Answer 7

X-linked recessive mutation

Question 8

What mode of inheritance does haemophilia use?

Answer 8

X-linked recessive

Question 9

What is odd about the gendered distribution of disease on an X-linked recessive disorder?

Answer 9

-Mainly males will be affected

-Females can be carriers and affected males are linked through females

Question 9

What is the probability of a daughter of a man with an X-linked condition being a carrier/sufferer of that condition?

Answer 9

100%-Daughters will always inherit their fathers’ X chromosome

Question 10

What makes a mutation recessive?

Answer 10

Its features won’t be in the phenotype unless it it homozygous

Question 11

What familial factor increases the risk of transferring autosomal recessive diseases

Answer 11

Consanguineous marriages

Question 12

What is the probability of offspring inheriting a condition that’s autosomally recessive from 2 carrier parents.

Answer 12

25%

Question 13

In what mode of inheritance has a ‘carrier’ lost a copy of a single gene yet can maintain normal function

Answer 13

Autosomal recessive

Question 14

What is the mode of inheritance of huntingtons’ disease and outline its mechanism of action

Answer 14

Huntingtons is autosomal dominant

-It is caused by unstable CAG repeats within chromosome 4, leading to accumulation of huntingtin and toxic cell death

Question 15

Through what mode of inheritance is a phenotype manifested if the allele is present in a heterozygote?

Answer 15

Autosomal dominant

Question 16

Outline the 3 autosomal dominant disorders types

Answer 16

Gain-of-function: Gene now makes a protein with a different, unwanted function

Dominant negative effect: The mutated form interferes with protein activity which it binds to.

Haploid insufficiency: Loss of one copy of the gene, so not enough protein for normal function can be made