Genetics & Punnett Square Practice
1.
Name: _________________________Date:_________Pd:________
What was Mendel’s contribution to genetics? Explain in NO LESS than 3 sentences.
2. Circle the HETEROZYGOUS genotypes:
Hh
aa
BB
XX
Tt
3. For each genotype, write whether it is a hybrid or purebred. H = hybrid and P = purebred
Hh _______
4.
aa _______
BB _______
XX _______
Tt _______
tt _______
In humans, the presence of a widow’s peak is dominant to no widow’s peak. What would the genotypes and phenotypes off the
offspring be if a homozygous dominant female with a widow’s peak was crossed with a male that did not have a widow’s
peak? Use R and r.
Punnett Square:
Genotype
Phenotype
%
The percent chance of children who will have a widow’s peak is __________________%.
5.
In purple people eaters, the dominant trait is to be one-eyed but occasionally a baby purple people eater will be born with three
eyes. If two heterozygous, one eyed parents produce offspring, will it be possible for them to have a three eyed child? Give
the genotypes and phenotypes of the offspring. Use E and e.
Punnett Square:
Genotype
Phenotype
The percent chance of children with three eyes is _________________%.
%
6.
In mice, brown fur is dominant to tan fur. A tan mouse is crossed with a heterozygous brown mouse. Predict the genotypes
and phenotypes of the offspring. Use T and t.
Punnett Square:
Genotype
Phenotype
%
The percent chance of baby mice with tan fur is ______________________%.
7. In pea plants green pods are dominant to yellow pea pods. Predict the genotypes and phenotypes of the offspring
of a cross between a homozygous green pea plant and a heterozygous pea plant. Use G and g.
Punnett Square:
Genotype
Phenotype
%
The percent chance of yellow pea pods would be ________________%.
8. In humans, a condition known as albinism occurs when the person inherits 2 recessive alleles. The person cannot
produce skin pigment. Normal skin pigment is dominant and albinism is recessive. If two parents who are both
heterozygous are crossed, what will the phenotypes and genotypes of the offspring be? Use A and a.
Punnett Square:
Genotype
Phenotype
%
The percent chance of normal offspring from this couple would be _____________%.
BONUS - Bob and Sally are a recently married couple. They both have blue eyes. Bob has blonde hair but Sally has red
hair. They are both healthy and of average height but both of them have a parent who has cystic fibrosis. Cystic Fibrosis
is a recessive disorder. If a child inherits a recessive allele from both parents, they will have breathing problems. Bob
and Sally are afraid that they could have a child with cystic fibrosis. Take on the role of a genetic counselor and give Bob
and Sally the % chances they will have of having typical children or children plagued with cystic fibrosis.
Punnett Square:
Genotype
Phenotype
%
The percent chance that Bob and Sally will have a child with cystic fibrosis is ________________%.