4 Genetic Disorders

define genetic disorder.

a health condition caused by abnormalities in the genome

what causes these abnormalities?

a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality.

How can these mutations occur?

• spontaneously before embryonic development (de novo).

• autosomal recessive inheritance - inherited from 2 parents who are carries of a faulty gene.

• autosomal dominant inheritance - inherited from a parent with the disorder.

is Huntingdon’s disease an autosomal dominant or recessive disorder?

• autosomal dominant

• mutated allele 1 parent is sufficient for child to be affected.

is Cystic fibrosis an autosomal dominant or recessive disorder?

• autosomal recessive

• mutated alleles have to be inherited from b oth parents for child to be affected.

what is X-linked recessive inheritance?

when a mutation in a gene on the X chromosome causes disease in:

• males who are hemizygous for the mutation (XY - they have only 1 X chromosome)

• females who are homozygous for the mutation (XX - they carry mutation on both X chromosomes)

define hemizygous

a person with one copy of a gene rather than 2, e.g. males have 1 X & Y chromosome, so they’re hemizygous for genes on the X chromosome.

why are males more likely to display phenotypes for genes that are sex-linked?

• males have only 1 X chromosome

• cos they have 1 copy, they express the characteristic of this allele even if its recesive.