Question

There are six people in the Fisher family. Olivia and Marcus are the parents. They have four children: Violet, Nathan, Jonas, and Claudia.
Neither Olivia nor Marcus have freckles.

What is Olivia's genotype?
What is Marcus' genotype?
What is the probability that each child has of inheriting freckles?
Both Marcus and Olivia are heterozygous for the hairline trait.

What is the probability that each of their children could inherit a widow's peak?
What is the probability that each of their children could inherit a straight hairline?
What is the probability that each of their children could be homozygous dominant for the trait?
Neither Marcus nor Olivia can roll their tongues.

How many of their children could be born with the ability to roll their tongues?
How many of their children could be hybrids?
What is the genotype of the whole family?
All four children have dimples.

What is likely the genotypes of their parents?
Do we know with certainty that one of the parents has to have dimples?
Both Olivia and Marcus are EE for the earlobe trait.

Among their children, what is the ratio of free earlobes to attached earlobes?
What percentage of the children are homozygous?
Marcus can not detect the bitter taste. Olivia has been found to be able to detect the bitter taste, but she is heterozygous for the trait.

What is the probability that each of their children could taste the ptc paper?
If Violet can not taste the ptc paper, what is Violet's genotype?
Given what you know, how many of the family can taste the ptc paper?

Answer 1

Answer and Explanation:

A) The allele for freckles is dominant (F), so if Neither Olivia nor Marcus has freckles, then their genotypes are recessive homozygote for the trait, this is "ff."

          1) Olivia genotype: ff

          2) Marcus genotype: ff

          3) 100% of their children will be recessive homozygote for the freckles gene, ff.

B) Hairline gene: Widow peak allele is dominant -W- over the strait hairline allele which is recessive -w-. Both Marcus and Olivia are heterozygous for the hairline trait, so both their genotypes are Ww for the trait.

1. The probability of getting children with a widow's peak is 75% or 3/4 of probability, (WW or Ww).
2. The probabilities for children to inherit strait hairline is 25% or 1/4 (ww).
3. The probability for the children to be homozygous dominant (WW) is 25% or 1/4.

C) Tongue´s roll trait: Tongue rolling is a dominant trait, T. Neither Marcus nor Olivia can roll their tongues, so their genotypes are tt.

1. None of their children will be born with the ability to roll their tongues.
2. None of their children will be hybrids, because both their parents are homozygous recessive for the trait.
3. The genotype of the whole family is "ww".

D) Dimple is dominant. There are high possibilities of getting the dimples dominant allele in a family that already express the trait.

1. If the four children have dimples, this means that both their parents could be dominant homozygote for the trait, "DD" or that one of them is homozygote and the other is heterozygote, "Dd", or that one of them is dominant homozygote "DD" and the other one is recessive homozygote "dd".
2. But one they must have dimples.

E) Free-lobule trait, E, is dominant over the attached-lobule trait, e.  Both parents are EE, homozygous dominant for the trait.  100% of the progeny will be homozygous dominant free lobules, EE. The ratio of free lobes to the attached lobes is 1 to 0.

F) The ability to taste bitter is dominant, T. So if Marcus cannot detect bitter taste, he is recessive homozygote for the trait, "tt". Olivia is a heterozygote for the trait, this is "Tt".

1. The probability that each of their children could taste the PTC paper is 50% or 2/4.
2. If Violet can not taste PTC paper her genotype is "tt".
3. The number of individuals that can taste PTC is 4 over 6.

Answer 2

Wow, this is a big question, but here goes. Freckles q: 1) Since freckles is the dominant phenotype, this means that Olivia must have the recessive phenotype, which is only given by the genotype ff. FF and Ff would both give freckles because, again, freckles is dominant. So any genotype with F_ would give freckles. 2)Same answer as #1. 3) Since they only have f alleles to pass on, both the dad and the mom will pass on one f each to 100% of their children. So all will have genotype ff and no freckles.
Hairline q: Since the parents are heterozygous, this means that their genotype has one of each allele to give Hh. (Even though you said they are quadruplets, I'm going to assume they are fraternal (different DNA) b/c otherwise they'd always have the same genotype if they are identical). 1) Okay, so when you do the Punnett square for Hh x Hh, you'll get 1HH:2Hh:1hh. Since widow's peak is dominant, any genotype with H_ gives the widow's peak. So, there are 3 options from the Punnett square, so you'll have 3 of the kids with widow's peak. Theres a 3/4 chance that a child will have widow's peak from these parents. 2) Since straight hairline is recessive, you need hh to get this phenotype and there is only one option. So, there will only be one child with the straight hairline. (1/4 chance). 3) Homozygous dominant means that you have two of the dominant allele, so HH. Since there is only 1 option, there is only one child with this genotype.
Tongue q: Since rolling the tongue is a dominant trait and the parents both can't roll their tongues, they must have a homozygous recessive genotype for this to happen (remember in dominance, any genotype with a dominant allele will give the dominant phenotype), so they have tt. 1) Since again they can only pass on t alleles, the kids will all have tt, so no one can roll their tongues. 2) None of them are hybrids because there was no variety in the genotypes or anything. Both parents had tt, so they were same in genotype. 3) She will have tt because of the above stated reasons.
Dimples q: Since all four kids have dimples, the dominant phenotype, they must all have the genotype D_ (either Dd or DD). 1) Since Marcus is a hybrid, this means that he had parents that were DD x dd to give him the genotype Dd. Since he has a recessive allele d in his genotype, Olivia must have all dominant alleles to make sure that each child has at least one dominant D. So, she must have the genotype DD. 2) Since she is DD, the dominant alleles will make her have dimples.
Earlobe q: 1) Since the parents are EE both, a cross of EE x EE will give EE genotype children. So, all children have EE, this means they all have free earlobes. So the ratio is 100% free to 0% attached earlobes. 2)Homozygous means they have two of the same alleles. Since all of them have EE, 100% of them are homozygous.
PTC q: Marcus has genotype bb and Olivia has genotype Bb because she is heterozygous. 1) The cross of bb x Bb gives 1Bb:1bb, So, 1/2 can taste the paper, so 50% can taste. 2) Since Violet can't taste the paper, she must be recessive and have the genotype bb. Since both of the boys can taste, they must have the genotypes Bb. Since 1/2 is already Bb, Claudia must be bb to help create the 50% that can't taste in the kids. 3)So, 2 people out of the family can taste the paper. Even though Olivia has Bb and should be able to taste, she can't. So, only Jonas and Nathan can taste the paper.
Pheww... done.. Hope this helps! :)