Topic 4-2

Question 1

Only males are affected
passed from father to all sons
Does not skip generations

Answer 1

Y-Linked traits

Question 2

Both males and females are usually affected; often more females than males are affected
Does not skip generations. Affected sons must have an affected mother. Affected daughters must have either an affected mother or an affected father
Affected fathers will pass the trait on to all their daughters
Affected mothers (if heterozygous) will pass the trait on to ½ of their sons and ½ of their daughters

Answer 2

X-linked dominant trait

Question 3

Usually more males than females are affected
Affected sons are usually born to unaffected mothers; thus the trait skips generations
Approximately ½ of a carrier (heterozygous) mother’s sons are affected
Never passed from father to son
All daughters of affected fathers are carriers

Answer 3

X-linked recessive trait

Question 4

Usually appears in both sexes with equal frequency
Both sexes transmit the trait to their offspring
Does not skip generations
Affected offspring must have an affected parent unless they possess a new mutation
When one parent is affected (heterozygous) and the other parent is unaffected, approximately half of the offspring will be affected
Unaffected parents do not transmit the trait

Answer 4

Autosomal dominant trait