QuestionSBA
QuestionChoice
One of the parents has a homozygous recessive genotype so the offspring has to inherit one recessive allele.

The other parent is heterozygous so 50% chance of inheriting another recessive gene.
10005837
b
0%
QuestionChoice
In autosomal recessive conditions, if both parents are carriers (heterozygous) there is 75% that children will not have the condition.
10005840
e
75%
QuestionChoice
CF is an autosomal recessive condition.

When one parent has CF the genotype must be homozygous recessive and the other parent is a heterozygous carrier.

50% of offspring would have CF but if the dominant allele was inherited from the carrier, 50% would be carriers.
10005836
a
50%
QuestionChoice
There is still a 50% chance of inheriting a dominant allele from the heterozygous carrier so not all will have the disease.

If this was a mitochondrial inheritance and the mother was affected, all would be affected.
10005839
d
100%
QuestionChoice
If both were heterozygous carriers, there would be a 25% of disease.

50% would be carriers and 25% are not carriers.

These chances don't change depending on previous children.
10005838
c
25%
Concept
Chapter
2693
4451
Autosomal recessive conditions
Topic
156
Medical Genetics
13714
A heterosexual couple attends a fertility clinic to discuss their options for conception.

One parent has Cystic Fibrosis (CF) and one parent is a known carrier.

They have a 5 year old child who does not have the disease. If they decide to conceive naturally what is the chance the second child will have CF?
a