GENETICS PROBLEMS
1. A man with a widow’s peak (WW) marries a woman with a continuous hairline (ww). What kind
of hairline will their children have?
a. Genotype of gametes produced: male = _______________, female = _______________
b. Show the cross here:
c. Children’s: genotype = ______________________, phenotype = ___________________
2. Suppose one of the children from the above problem (Ww) marries someone who is also
heterozygous (Ww). What type of hairline will their children have?
a. Genotype of gametes produced: male = _______________, female = _______________
b. Show the cross here:
c. Children’s: genotype = ______________________, phenotype = ___________________
3. A woman is homozygous dominant for short fingers (SS). She marries a man who is
heterozygous for short fingers (Ss).
a. Genotype of gametes produced: male = _______________, female = _______________
b. Show the cross here:
c. Will any of their children have long fingers(ss), yes or no? _______________
d. Could any of the grandchildren of the above couple potentially have long fingers? Why
or why not? (Hint: It may help to show any possible crosses.)
4. Jane and John are expecting a baby and know that they are both carriers (i.e. heterozygous) of
cystic fibrosis (Cc). What is the probability that their child will have cystic fibrosis (cc)? What is
the probability that their child will be a carrier of cystic fibrosis?
Chance of child being:
___________ disease free; genotype = _______________
___________ cystic fibrosis carrier; genotype = _______________
___________ cystic fibrosis; genotype = _______________
5. You have freckles and dimples (FfDd). Your significant other has freckles but no dimples (Ffdd).
What is the chance your child would have both recessive phenotypes: no freckles and no
dimples (ffdd)? (Hint: do a dihybrid cross using the foil method)
a. Genotype of gametes produced: male = _______________, female = _______________
b. Show the cross here:
c. % no freckles and no dimples: _________________________
6. All the offspring of a cross between a black-eyed mendelien and an orange-eyed mendelien
have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed
mendeliens?
7. Hemophilia is a recessive genetic disorder whose disorder allele, which we’ll call a, is located on
the X chromosome. What are the chances that parents with the following genotypes will have a
child with hemophilia?
a. XAXA x XaY
b. XAXa x XaY
c. XAXa x XAY
d. XaXa x XAY
8. If blue flower color (B) is dominant to white flower color (b), what are the genotypes of the
parents in the following genetic cross: blue flower x white flower yields only blue-flowered
offspring?
Mother’s genotype: ____________
Father’s genotype: ____________
9. The fruit pods of peas can be yellow or green. In one of his experiments, Mendel crossed plants
that were homozygous for the allele for yellow fruit pods with plants that were homozygous for
the allele for green fruit pods. All fruit pods in the F1 generation were green. Which allele is
dominant, the one for yellow or the one for green? Briefly explain why, it may help to show the
crosses for each.
10. Color-blindness is a sex-linked gene carried on the X chromosome. A color-blind man and his
wife, with normal vision, have a color-blind daughter. What is the probability that their newborn
son will also be color blind?
11. Use this pedigree of a to determine the genotypes for the
following individuals. The trait is recessive.
Female
Male
Affected
Unaffected