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Name ____________________________________ Date ________________
GENETIC PROBLEMS
1. In Peas, THE GENES FOR TALLNESS (t) IS DOMINANT TO THE GENE
FOR SHORTNESS (T). What offspring phenotypes would be expected from the
following crosses, and what proportions? Show punnett squares!
a. heterozygous x heterozygous
Genotypes of parents: _________________________
Genotypes of Offspring:
Phenotypes of Offspring:
Ratios:
_________________________
_________________________
_________________________
b. hybrid x homozygous tall
Genotypes of parents: _________________________
Genotypes of Offspring:
Phenotypes of Offspring:
Ratios:
_________________________
_________________________
_________________________
c. homozygous short x pure bred tall
Genotypes of parents: _________________________
Genotypes of Offspring:
Phenotypes of Offspring:
Ratios:
_________________________
_________________________
_________________________
2. A pure bred purple grape is crossed with a pure bred white grape. Purple is
dominant over white.
a. Diagram the cross and give the phenotypes of the 1st generation.
Genotypes of parents: _________________________
Genotypes of Offspring, (1st Generation):_________________________
Phenotypes of Offspring: (1st Generation): _______________________
b. Next take two members of the 1st generation and cross them. (This is a 2nd
generation cross.)
Genotypes of parents: _________________________
Genotypes of Offspring, (2nd Generation):_________________________
Phenotypes of Offspring: (2nd Generation): _______________________
3. On the basis of Mendel’s hypothesis and observations, predict the results from the
following crosses in garden peas: (R = round, r = wrinkled)
a. A round homozygous dominant variety crossed with a wrinkled variety.
Genotypes of parents: _________________________
Genotypes of Offspring:_________________________
Phenotypes of Offspring: _______________________
b. The offspring of problem ‘a’ self-pollinated, (crossed with itself).
Genotypes of parents: _________________________
Genotypes of Offspring:_________________________
Phenotypes of Offspring: _______________________
c. The offspring of problem ‘a’ crossed with the original round parent.
Genotypes of parents: _________________________
Genotypes of Offspring:_________________________
Phenotypes of Offspring: _______________________
d. The offspring from problem ‘a’ crossed with the original wrinkled parent
variety.
Genotypes of parents: _________________________
Genotypes of Offspring:_________________________
Phenotypes of Offspring: _______________________
4. If blue eye color in humans is recessive to the other colors, could:
a. 2 brown-eyed parents have a blue-eyed child?
__________________
b. 2 blue-eyed parents have a brown-eyed child?
__________________
5. Albinism, the inability to produce chlorophyll, is a recessive trait in a number of
plant species. If a tobacco plant known to be heterozygous for albinism is selfpollinated and 600 of its seeds are germinated:
Genotypes of parents: _________________________
a. How many seedling would be expected to be albino?_______________
b. How many seedlings would be expected to have the parental genotype?____________
6. In Holstein Cattle, the spotting of the coat is due to a recessive gene while a solid
colored coat is dominant. What types of offspring might be produced by a cross
between two spotted animals?
___________________
Genotypes of parents: _________________________
7. In cats, the gene for short hair is dominant over the gene for long hair, (Angora).
A short-haired tomcat is mated with an Angora female. She bears eight kittens,
six short-haired and two with long hairs. How do these numbers compare with
the expected ratio?
Observed Genotypes of Offspring:_________________________
Observed Phenotypes of Offspring: _______________________
Genotypes of parents: _________________________
Expected Genotypes of Offspring:_________________________
Expected Phenotypes of Offspring: _______________________
a. If you mated these same cats four more times and obtained a total of forty
offspring would you expect the results to be a close approximation of the
expected ration? Explain.
8. A women has a rare abnormality of the eyelids called ptosis, which makes it
impossible for her to open her eyes completely. The condition has been found to
depend on a single dominant gene (P). The women’s father has ptosis, but her
mother had normal eyelids. Her father’s mother had normal eyelids. Use small
(p) for normal.
a. What are the probable genotypes of the woman, her father, and mother?
i. Woman’s genotype:
____________________
ii. Her father’s genotype:
____________________
iii. Her mother’s genotype:
____________________
b. Show a pedigree, (family tree of genotypes), of the family’s traits.
c. What proportion of her children will be expected to have ptosis if she
marries a man with normal eyelids?
Genotypes of parents: _________________________
Genotypes of Offspring:_________________________
Phenotypes of Offspring: _______________________