7. Genotype,phenotype & Inheritance Flashcards
What is hemizygous?
Only one allele of a gene on the X chromosome (males only)
What is an example of co-dominance?
Human ABO blood types - type AB expresses both A and B antigens on its surface
Alleles A and B are dominant over O
What is an example of an autosomal recessive disease.
Cystic fibrosis
What is the chance of 2 heterozygotes passing a recessive disease onto their offspring?
25%
How would you recognise an autosomal recessive trend on a family tree?
Tends to ‘come out of nowhere’
Can skip generations
Males and females equally affected
Both parents of affected individual must be heterozygous carriers
What is an example of an autosomal dominant disease?
Huntington’s disease
How would you recognise an autosomal dominant trait in a family tree?
Does not skip generations
Males and females equally affected
What is the chance that a parent heterozygous for a disease will pass it on to their offspring?
50%
What is an example of an X-linked recessive disease?
Haemophilia A
How would you recognise haemophilia A on a family pedigree?
Males more likely to be affected than females
Affected males cannot pass to their sons (give them their Y)
How can female offspring be affected by an X-linked recessive disease?
If her mother is a carrier and her father is affected
What is polygenic inheritance?
When more than one gene is involved in producing a phenotype
What is the inheritance pattern of albinism?
Recessive and polygenic - 2 genes A1 and A2 and 4 alleles
What are genes that are on the same chromosome called?
Linked genes
How do linked genes differ at meiosis?
They do not show independent assortment
