Genetic Diseases

Q1.Some genetic disorders are caused by alleles inherited from the parents.
(a) What are alleles?
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(1)

(b) Describe how embryos can be screened for the alleles that cause genetic disorders.
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(4)

(c) Polydactyly is a genetic disorder that leads to extra fingers or toes.
Polydactyly is caused by a dominant allele, D.
The photograph shows the hand of a person with polydactyly.

A man has polydactyly. His wife does not have polydactyly.
This couple‘s children have a 50% chance of having polydactyly.
Draw a genetic diagram