Phenotype and genotype

Question 1

Autosomal recessive inheritance key points (2 things)

Answer 1

• Males and females equally affected
• Heterozygotes are carriers

Question 2

Autosomal dominant inheritance key points (3 things)

Answer 2

• Male and females equally affected
• Heterozygotes affected
• Disease can’t skip a generation

Question 3

X-linked recessive inheritance key points (3 things)

Answer 3

• Males and females unequally affected
• Every affected male will have at least a heterozygous carrier mother
• Every affected female will have an affected father and a carrier mother

Question 4

X-linked dominant inheritance- what it is and example (2 things)

Answer 4

• Affected males cannot give trait to sons but will give it to all daughters
• e.g. fragile X syndrome

Question 5

What is penetrance and expressivity (2 things)?

Answer 5

• Penetrance describes whether there is clinical expression of a phenotype in a person (symptom)
• Expressivity describes the difference in clinical presentation between 2 people with the same genotype (severity)