Question

1. this pedigree shows the inheritance of tay - sachs in a family. tay - sachs is a recessive disorder that causes cells to be unable to break down waste products. these wastes build up in brain cells and cause damage and eventual death. fill out the genotypes of each of the family members.

tt = normal
tt = carrier
tt = disease

1. this pedigree shows the inheritance of cystic fibrosis in a family. this disease causes mucus to build up in the lungs, leading to breathing difficulty and infections

ff =
ff =
ff =
fill out the genotypes of each of the family members.
add to the chart to show the youngest male (4th) generation marrying and having a child with cf.

1. this pedigree shows the inheritance of sickle cell disease (recessive). fill out the genotypes of the family.

aa = normal
aa = carrier
aa = sickle cell disease

Explanation:

Question 3 (Tay - Sachs Inheritance)

Step 1: Analyze the first - generation parents

The first - generation parents (the top - most couple) have a daughter with Tay - Sachs (tt). Since they are normal (do not have the disease), their genotypes must be Tt (because to have a child with tt, each parent must contribute a t allele, and since they are normal, they must also have a T allele). So the first - generation mother (circle) and father (square) are Tt and Tt.

Step 2: Analyze the affected daughter in the first generation

The affected daughter (filled circle) has the genotype tt (because Tay - Sachs is recessive, and she has the disease).

Step 3: Analyze the normal son in the first - generation offspring

The normal son (unfilled square) from the first - generation parents (Tt x Tt) can have a genotype of TT or Tt. But since his children (in the next generation) include affected individuals (tt), he must be a carrier (Tt). Because if he were TT, all his children would get a T from him, and they couldn't be tt (they would need two t alleles, one from each parent).

Step 4: Analyze the wife of the normal son in the second generation

The wife of the normal son (Tt) in the second generation (unfilled circle) must be a carrier (Tt) as well, because they have children with tt. For a child to be tt, both parents must contribute a t allele. So she is Tt.

Step 5: Analyze the affected sons in the third generation

The affected sons (filled squares) in the third generation have the genotype tt (recessive disease).

Step 6: Analyze the normal daughter in the third generation (from Tt x Tt)

The normal daughter (unfilled circle) in the third generation from Tt x Tt can be TT or Tt. But looking at the next family (the right - most family in the pedigree), we can further analyze.

Step 7: Analyze the right - most family in the pedigree (third - generation couple)

The third - generation couple (unfilled circle and unfilled square) has a daughter with tt. So both parents must be Tt (because they are normal but have a child with tt). The normal son (unfilled square) in their family has a genotype of TT or Tt, but since his sister is tt, his parents are Tt x Tt, so he can be TT or Tt. The affected daughter (filled circle) is tt.

Question 4 (Cystic Fibrosis Inheritance)

Step 1: Determine the meaning of genotypes

Cystic fibrosis is a recessive disorder. So:

• FF: normal (homozygous dominant, no disease - causing alleles)
• Ff: carrier (heterozygous, has one normal and one disease - causing allele)
• ff: disease (homozygous recessive, has two disease - causing alleles)

Step 2: Analyze the first - generation parents

The first - generation parents (unfilled circle and unfilled square) have a daughter with ff (filled circle). So both parents must be Ff (because they are normal but have a child with ff. For a child to be ff, both parents must contribute an f allele, so they must be carriers (Ff)).

Step 3: Analyze the affected daughter in the second generation

The affected daughter (filled circle) has genotype ff.

Step 4: Analyze the other children in the second generation

The other children (unfilled circle, filled square, unfilled circles, unfilled square) from Ff x Ff parents:

• The unfilled circles and square can be FF or Ff. But the filled square (affected son) has genotype ff. The unfilled circle who marries the affected son (ff) must be Ff (because their child is ff. So she is Ff, and he is ff, so their child (filled square) is ff (since he gets f from both parents)).
• The unfilled square who marries the affected daughter (ff) must be Ff (because their children: the unfilled circle and square. For a child to be normal, if one parent is ff, the other must contribute an F. But since the affected daughter is ff, the husband (unfilled square) must be Ff to have children. Their affected daughter (filled circle) is ff, so she gets f from both parents (father is Ff, mother is ff, so she gets f from mother and f from father (since father is Ff, he can pass f)). The unfilled circle in their family is Ff (gets F from father and f from mother) or FF (gets F from father and F from mother, but since mother is ff, she can only pass f, so the child must be Ff). The unfilled square in their family is Ff (gets F from father and f from mother) or FF (same reasoning as above, must be Ff because mother is ff).

Question 5 (Sickle Cell Disease Inheritance)

Step 1: Analyze the first - generation parents

The first - generation parents: unfilled square (AA or Aa) and filled circle (aa, since she has sickle cell disease). Their children: filled squares (aa) and unfilled circles (Aa, because they get A from father and a from mother).

Step 2: Analyze the second - generation couple (unfilled circle and filled square)

The unfilled circle (Aa) marries a filled square (aa). Their daughter (filled circle) is aa (gets a from both parents: mother is Aa (can pass a), father is aa (passes a)). The unfilled square (their son) is Aa (gets A from mother and a from father).

Step 3: Analyze the other second - generation filled square

The other second - generation filled square (aa) marries an unfilled circle (Aa). Their children:

• The filled square (son) is aa (gets a from both parents: father is aa, mother is Aa (passes a)).
• The unfilled circles (daughters) are Aa (get A from mother and a from father).
• The filled circle (daughter) is aa (get a from both parents: father is aa, mother is Aa (passes a)).
• The unfilled square (son) is Aa (get A from mother and a from father).

Answer:

s:

Question 3 (Tay - Sachs)

• First - generation mother (circle): Tt
• First - generation father (square): Tt
• Affected daughter (filled circle): tt
• Normal son (unfilled square): Tt
• Wife of normal son (unfilled circle): Tt
• Affected sons (filled squares): tt
• Normal daughter (unfilled circle): Tt (or TT, but more likely Tt due to family history)
• Right - most third - generation parents (unfilled circle and square): Tt and Tt
• Normal son (unfilled square) in right - most family: Tt (or TT)
• Affected daughter (filled circle) in right - most family: tt

Question 4 (Cystic Fibrosis)

• FF: normal
• Ff: carrier
• ff: disease
• First - generation parents (circle and square): Ff and Ff
• Affected daughter (filled circle): ff
• Other children in second generation:
• Unfilled circle: Ff (or FF)
• Filled square: ff
• Unfilled circles: Ff (or FF)
• Unfilled square: Ff (or FF)
• Second - generation couple (unfilled circle and filled square): Ff and ff
• Their child (filled square): ff
• Second - generation couple (unfilled square and filled circle): Ff and ff
• Their children:
• Unfilled circle: Ff
• Unfilled square: Ff
• Filled circle: ff

Question 5 (Sickle Cell Disease)

• First - generation parents:
• Unfilled square: Aa
• Filled circle: aa
• Second - generation children:
• Filled squares: aa
• Unfilled circles: Aa
• Second - generation couple (unfilled circle and filled square): Aa and aa
• Their children:
• Unfilled square: Aa
• Filled circle: aa
• Second - generation couple (filled square and unfilled circle): aa and Aa
• Their children:
• Filled square: aa
• Unfilled circles: Aa
• Filled circle: aa
• Unfilled square: Aa