The Fisher Family
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?
How many children have freckles?
Both Marcus and Olivia are heterozygous for the hairline trait.
How many of their children have a Widow's peak?
How many have a straight hairline?
How many children are homozygous dominant for the trait?
Neither Marcus nor Olivia can roll their tongues.
How many of their children can roll their tongues?
How many cannot?
What is Violet's genotype?
All four children have dimples.
If Marcus is a hybrid, what is Olivia's genotype?
Does she have dimples?
Both Olivia and Marcus are EE for the earlobe trait.
What is the ratio of free earlobes to attached earlobes?
What percentage of the children are homozygous?
Marcus's genotype for eye color is bb. Olivia has brown eyes, but she is heterozygous for the trait.
What percentage of the children have blue eyes?
If Violet has green eyes and Jonas has brown eyes, what is Claudia's genotype?
How many people in the family have blue eyes?
Answers
1. Having no freckles is recessive, so two copies of the allele are required, therefore both parents are ff, and each can only produce a single gamete f, so all the children will be ff and like their parents have no freckles.
You can now solve exactly the same problem for tongue rolling, as not being able to roll the tongue is recessive.
You can also, solve the ear lobes problem as you know that both parents are homozygous for free earlobes and this is dominant.
2. Hairline, both are heterozygous - a widow's peak is dominant W, straight is recessive w, both have widow's peak and genotype Ww
If you cross Ww x Ww each parent can produce 2 gametes, W or w and children could be WW, Ww, wW or ww. The last will have a straight hair line.
3. Dimples. Having dimples is dominant. Dad is a hybrid, so Dd. All of the children has dimples so none is dd. Therefore mum has not passed on a d allele to her children and so her genotype is DD.
DD x Dd mum produces only D gametes, dad D and d, so children are either DD or Dd.
4. Tasting. Dad is bb recessive, as a heterozygote mum is a non-taster, non tasting is dominant.
So bb x Bb. Dad produces only b gametes and mum either B or b, so children are either Bb or bb.
Those are all of the crosses and the outcomes, so you should be able to answer all of the questions now.