GENETICS PROBLEMS
Do these problems on binder paper.
You will need to review the meanings of the following terms: Genotypes, Phenotypes, dominant, recessive, cross, homozygous, heterozygous, pure-breeding, and hybrid.
Example Problem:
In chickens, white colored feathers are recessive to brown colored feathers. A pure breeding white rooster is bred to 3 hens: (1) a pure breeding white, (2) a pure breeding brown, and (3) a hybrid brown. Write out the 3 crosses.
RULES:
1. Choose a letter to represent the dominant allele and capitalize it (choose a letter that is easy to distinguish between upper-case and lower-case).
2. Use the same letter but use lower case to represent the recessive allele.
3. Put the male on the left of the square and the female on the top.
4. Write "genotype" and "phenotype" below the square.
5. Use "x" to indicate a cross.
6. Write the dominant allele first if you are writing out a hybrid.
Here's how…
(1) Pure white rooster x Pure white hen
bb x bb
(2) Pure white rooster x Pure Brown Hen
bb x BB
(3) Pure white rooster x Hybrid brown Hen
bb x Bb
Try these problems.
#1-3 Brown: Dominantwhite: Recessive
1. Hybrid brown rooster is crossed with a heterozygous hen.
2.Homozygous white rooster is crossed with a heterozygous hen.
3. Pure brown male is crossed with hybrid brown female.
4.In garden peas, tall vines are dominant and short vines are recessive. If a homozygous tall plant is crossed with a homozygous short plant, what genotypes are possible in the F1 generation?
5. In laboratory mice, the normal gray color is dominant over the albino (all white) color. Starting with purebred albino and purebred gray as parents, what is the ratio of phenotypes in the F2 generation?
6. In chickens, black color is dominant over red. A red hen is crossed with a homozygous black rooster. What will the phenotypes of the F1 generation be?
Now do a cross of two of the F1 offspring. This gives you the F2 generation. What are the possible phenotypes of the F2 generation? What is the ratio of these phenotypes?
7. NOTE: In humans, brown eyes (B) are dominant over blue eyes (b).
A brown-eyed man marries a blue-eyed woman and they have 2 children, both brown-eyed. What are the probable genotypes of all individuals in the family?
8.A blue-eyed man, both of whose parents were brown-eyed, marries a brown-eyed woman whose father was brown-eyed and whose mother was blue-eyed. They have one child who is blue-eyed. What are the genotypes of all members of this family?
9. A hen and a rooster produce 15 red offspring and 49 black offspring. What are the phenotypes and the genotypes of the parents? If your answer is correct, why were there not 17 red offspring and 47 black?
If one of the red daughters hens were mated with her father (it's okay with chickens), what phenotypes would you expect to find among the progeny (offspring)?
10. A shorthaired (short hair is dominant) homozygous guinea pig is mated to a longhaired guinea pig. Show the Punnett Square cross and give the ratio of the possible offspring.
#1-3: Brown:dominant; white: recessive
1. Hybrid brown rooster is crossed with a heterozygous hen.
2.Homozygous white rooster is crossed with a heterozygous hen.
3. Pure brown male is crossed with hybrid brown female.
4.In garden peas, tall vines are dominant and short vines are recessive. If a homozygous tall plant is crossed with a homozygous short plant, what genotypes are possible in the F1 generation?
5. In laboratory mice, the normal gray color is dominant over the albino (all white) color. Starting with purebred albino and purebred gray as parents, what is the ratio of phenotypes in the F2 generation?
6. a) In chickens, black color is dominant over red. A red hen is crossed with a homozygous black rooster. What will the phenotypes of the F1 generation be?
b) Now do a cross of two of the F1 offspring. This gives you the F2 generation. What are the possible phenotypes of the F2 generation? What is the ratio of these phenotypes?
#7-8: In humans, brown eyes (B) are dominant over blue eyes (b).
7. A brown-eyed man marries a blue-eyed woman and they have 2 children, both brown-eyed. What are the probable genotypes of all individuals in the family?
8.A blue-eyed man, both of whose parents were brown-eyed, marries a brown-eyed woman whose father was brown-eyed and whose mother was blue-eyed. They have one child who is blue-eyed. What are the genotypes of all members of this family?
9. A hen and a rooster produce 15 red offspring and 49 black offspring. What are the phenotypes and the genotypes of the parents? If your answer is correct, why were there not 17 red offspring and 47 black?
If one of the red daughters hens were mated with her father (it's okay with chickens), what phenotypes would you expect to find among the progeny (offspring)?
10. A shorthaired (short hair is dominant) homozygous guinea pig is mated to a longhaired guinea pig. Show the Punnett Square cross and give the ratio of the possible offspring.
GENETICS PROBLEMS- Answer SheetName ______
1.2.
3.4.
Possible F1 Genotypes: ______
5.PARENTS: ______x ______F1 "parents": ______x ______
F2 Phenotypic Ratio: ______
6.
F2 Phenotypic Ratio: ______
______
7.______x ______
______
8.______x ______x ______
______
______
9.Parent Phenotypes: ______
Parent Genotypes: ______
(Hint: Think about the ratio that 15 red and 49 black is closest too.)
______
______
Expected Offspring Phenotypes:
______
10.
Genotypic Ratio: ______
Phenotypic Ratio: ______