Question

example 1: tracing the path of an autosomal recessive trait
trait: fanconi anemia
forms of the trait:
the dominant form is normal bone marrow function - in other words, no anemia.
the recessive form is fanconi anemia. individuals affected show slow growth, heart defects, possible bone marrow failure and a high rate of leukemia.
a typical pedigree for a family that carries fanconi anemia. note that carriers are not indicated with half - colored shapes in this chart.
analysis questions.
to answer questions #1 - 5, use the letter \f\ to indicate the recessive fanconi anemia allele, and the letter \f\ for the normal allele.

1. what is arlenes genotype?
2. what is georges genotype?
3. what are ann & michaels genotypes?
4. most likely, sandras genotype is
5. list three people from the chart (other than george) who are most likely carriers of fanconi anemia.

Explanation:

Step1: Analyze Arlene's genotype

Since Arlene has the trait (Falconi anemia which is recessive), her genotype must be $ff$.

Step2: Analyze George's genotype

George does not have the trait. But he has children with the trait, so he must be a carrier. His genotype is $Ff$.

Step3: Analyze Ann & Michael's genotypes

Ann and Michael do not have the trait, and they have a child (Carla) with the trait. So they must both be carriers with genotype $Ff$.

Step4: Analyze Sandra's genotype

Sandra does not have the trait and has a child (Tom) with the trait. So she is most likely a carrier with genotype $Ff$.

Step5: Identify carriers

Since Tom has the trait and his parents are Sandra and George (carrier), Sandra is a carrier. Also, Ann and Michael are carriers as they have a child with the trait.

Answer:

1. $ff$
2. $Ff$
3. $Ff$ (Ann), $Ff$ (Michael)
4. $Ff$
5. Sandra, Ann, Michael