GENETICS PROBLEMS - Part 1
BIOL 1406
 
 

MONOHYBRID CROSS PROBLEMS:

 Characteristic of Mendel's Peas

Dominant allele

Recessive allele

        Flower Color            Purple (F)               white (f)
        Seed Color            Yellow (G)               green (g)
        Seed Shape            Round (R)               wrinkled (r)
        Stem Length            Tall (T)               dwarf (t)
 
1. A plant that is homozygous for yellow seeds is crossed with a plant that is homozygous for green seeds.  What percentage of the F1 generation would you expect to have yellow seeds?
 
2. A plant that is heterozygous for tall stem length is crossed with a plant that has dwarf stem length.  What percentage of the F1 generation would you expect to have dwarf stem length?
 
3. A plant that has wrinkled seeds is crossed with a plant that is heterozygous for round seeds.  What percentage of the F1 generation would you expect to have round seeds?
 
4. A plant that is heterozygous for purple flowers is self-pollinated (crossed with itself).  What would be the expected phenotype ratio of the F1 generation?
 
5. A plant that is homozygous for tall stem length is crossed with a plant that is homozygous for dwarf stem length.  What would be the phenotype of all the offspring in the F1 generation?
 
6. A gardener has a plant that produces yellow seeds.  If he does a test cross, what would be the genotype of the plant he would use for the test?
 
If the test cross produces offspring that are 48% yellow and 52% green, what is the genotype of the original plant?
 
 

DIHYBRID PROBLEMS:

 
7. A plant that is homozygous for green seeds and heterozygous for tall stem length is crossed with a plant that is heterozygous  for yellow seeds and homozygous for tall stem length.  What is the expected phenotype ratio of the F1 generation.
 
8. A plant that is homozygous for purple flowers and homozygous for dwarf stem length is crossed with a plant that is homozygous for white flowers and homozygous for tall stem length.  What are the genotypes of all the F1 generation -- WITHOUT WORKING THE PUNNETT SQUARE!
 
HUMAN TRAIT Dominant Allele Recessive Allele
Dimples D - have dimples d - no dimples
Earlobes E - free/unattached e - attached
Eye Color B - pigmented iris/brown b - non-pigmented/blue
Freckles F - freckles present f - no freckles
Little Finger L - bent little finger l -  straight little finger
Tongue-Rolling R - can roll tongue r - can't roll tongue
 
9. Two parents have the following genotypes: Dad - BbEe and Mom - bbee.  What are the phenotypes of the two parents?
 
What chance is there that a child of theirs would have blue eyes and attached earlobes?
 
10. Dad is heterozygous for freckles and homozygous for no dimples.  Mom is homozygous for no freckles and heterozygous for dimples.  What is the genotype of each parent?  What is the percentage chance that a child of theirs would have both freckles and dimples?
 
12. A man is able to roll his tongue and has blue eyes?  His wife is not able to roll her tongue and has brown eyes.  If they have a child that cannot roll his tongue and has blue eyes, what is the genotype of both parents?
 
 

DIHYBRID CROSSES w/ GUINEA PIGS:

 
GUINEA PIG TRAIT Dominant Allele Recessive Allele
Fur Texture R - Rough r - smooth
Fur Color B - Black b - white
 
13. A male guinea pig is heterozygous for rough fur and homozygous for black color.  The female guinea pig is homozygous for smooth fur and heterozygous for black color.  What is the genotype for each of the parents?
 
What are the four possible phenotype combinations in their offspring and the percent chance for each?
 
14. If you mate two guinea pigs who are both heterozygous for rough fur and black in color, what would be the phenotype ratio of their offspring?
 
15. If a guinea pig that is heterozygous for rough fur and white in color is mated with a guinea pig that is heterozygous for both rough fur and black color, what would be the expected genotype ratio in the F1 generation?
 
16. A breeder has a guinea pig that is black with rough fur.  If this guinea pig is mated with a white, smooth guinea pig and the offspring produced are 4 black with rough fur and 3 white with rough fur, what is the genotype of the black, rough parent guinea pig?