Download Monohybrid Crosses

MONOHYBRID PRACTICE PROBLEMS:
Please follow directions below: Use each other, notes, e-text, and even the internet if you need help…there is no excuse
to not have this completed or at the very least an educated attempt!
Complete the following problems on a separate sheet of loose-leaf paper. You may choose your own letters to
represent the different traits if they are not provided for you. Be sure to read thoroughly and think critically (this will
solve many problems). Show all work!
1. In gerbils, brown fur color is dominant to white fur color. If a homozygous dominant gerbil is mated with a
heterozygous gerbil what are the possible genotypes and phenotypes of the offspring. (Use ratios and percent’s)
2. In pea plants, green seed color is dominant to yellow seed color. If a heterozygous pea plant is crossed with a plant
that is homozygous recessive for seed color, what is the probability that the offspring will have green seeds?
3. If all of the offspring of a particular cross have the genotype Gg, what must the genotype of the parents be?
4. In fruit flies normal wings (W) is dominant over vestigial wings (w). The results of a cross, of
two fruit flies, give the following results:
Normal wing 793
Vestigial wing 811
What are the genotypes of the parents of the offspring? Use a Punnett square to prove your answer.
5. The gene for no eyes in fruit flies is recessive the gene for normal eyes is dominant. An eyeless male is crossed with a
female who is homozygous for normal eyes. They produce 200 offspring, their offspring cross breed to form 3000
offspring. Determine the probabilities of the following
How many of the 200 offspring (F1) are blind?
How many of the 3000 offspring (F2) have normal vision?
How many of the 200 offspring (F1) are heterozygous?
How many of the 3000 offspring (F2) are heterozygous?
Complete the following problems on a separate sheet of loose-leaf paper. You may choose your own letters to
represent the different traits if they are not provided for you. Be sure to read thoroughly and think critically (this will
solve many problems). Show all work!
1. In Border Collies, black coat (B) is dominant to red coat (b). A breeder has a black male that has won numerous
awards. The breeder would like to use the dog for breeding if he is purebred or BB. To learn this information, she
testcrosses him with a red female (bb). Answer the following questions A, B, C, and D.
A.
If the black male is BB, what kind of gamete (sperm) can he produce?
B. If the red female is bb, what kind of gamete (eggs) can she produce?
C.
If the black male is Bb, what kind(s) of gametes (sperm) can he produce?
D.
If any of the puppies are red, what is the father's genotype?
2. Firebreathing (F) is dominant in dragons. NON-firebreathing (f) is recessive.
You have a firebreathing dragon. What are its possible genotypes?
E.
The dragon you should use to do a test cross should have:
genotype?
phenotype?
Show the results of test crossing BOTH OF THE POSSIBLE PARENT GENOTYPES:
An actual test cross results in a litter with:
6 firebreathing dragons
1 NON-firebreather
What is the genotype of your firebreathing dragon?
3. Why do you always perform a test cross using a homozygous recessive individual?
4. If your test cross results in offspring that show both the dominant and recessive traits what does the genotype of your
unknown parent have to be (homozygous dominant or heterozygous)? Show Proof!
5. If your test cross results in offspring that show only the dominant trait what is most likely the genotype for your
unknown parent (homozygous dominant or heterozygous)? Show Proof!
Complete the following problems on a separate sheet of loose-leaf paper. You may choose your own letters to
represent the different traits if they are not provided for you. Be sure to read thoroughly and think critically (this will
solve many problems). Show all work!
1. In some chickens, the gene for feather color is controlled by codominance. The allele for black is CB and the allele for
white is CW. The heterozygous phenotype is known as erminette (black and white spotted).
a. What is the genotype for black chickens? ____
b. What is the genotype for white chickens? ____
c. What is the genotype for erminette chickens? ____
2. If two erminette chickens were crossed, what is the probability that (show Punnett Squares!)
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____
3. A black chicken and a white chicken are crossed. What is the probability that they will have (show Punnett Squares!)
erminette chicks? ____%
Parents: ____ X ____
4. In some cattle the genes for brown hair and for white hair are co-dominant. Cattle with alleles for both brown and
white hair, have both brown and white hairs. This condition gibes the cattle a reddish color, and is referred to as Roan.
For each of the following construct a Punnett square and give the genotypic and phenotypic ratios of the offspring.
a. A brown cow and white bull.
b. A brown cow and roan bull.
c. A white cow and roan bull.
d. A roan cow and roan bull.
5. Mrs. Clink is type “A” and Mr. Clink is type “O.” They have three children named Matthew, Mark, and Luke. Mark is
type “O,” Matthew is type “A,” and Luke is type “AB.” Based on this information:
a. Mr. Clink must have the genotype ______
b. Mrs. Clink must have the genotype ______ because ___________ has blood type ______
c. Luke cannot be the child of these parents because neither parent has the allele _____.
Complete the following problems on a separate sheet of loose-leaf paper. You may choose your own letters to
represent the different traits if they are not provided for you. Be sure to read thoroughly and think critically (this will
solve many problems). Show all work!
1. In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (R’). The
heterozygous genotype is expressed as pink.
a. What is the phenotype of a plant with the genotype RR? ___________
b. What is the phenotype of a plant with the genotype R’R’? ___________
c. What is the phenotype of a plant with the genotype RR’? ___________
2. A pink-flowered plant is crossed with a white-flowered plant. What is the probability of producing a pink-flowered
plant? ____%
Parents: ____ X ____
3. What cross will produce the most pink-flowered plants? Show a punnett square to support your answer.
Parents: ____ X ____
4. Two short-tailed (Manx) cats are bred together. They produce three kittens with long tails, five short tails, and two
without any tails. From these results, how do you think tail length in these cats are inherited? Show the genotypes for
both the parents and the offspring to support your answer.
Complete the following problems on a separate sheet of loose-leaf paper. You may choose your own letters to
represent the different traits if they are not provided for you. Be sure to read thoroughly and think critically (this will
solve many problems). Show all work!
In fruit flies, eye color is a sex linked trait. Red (XR) is dominant to white (Xr).
1. What are the sexes and eye colors of flies with the following genotypes:
a. X R X r
_________________
b. X R Y _________________
c. X R X R
_________________
d. X r Y _________________
2. What are the genotypes of these flies:
a. white eyed, male ____________
b. red eyed female (heterozygous) ________
c. white eyed, female ___________
d. red eyed, male ___________
3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y .
4. Show a cross between a pure red eyed female and a white eyed male.
a. What are the genotypes of the parents ___________& _______________
b. How many are white eyed, male___
c. How many are white eyed, female ___
d. How many are red eyed, male ____
e. How many are red eyed, female ____
5. Show the cross of a red eyed female (heterozygous) and a red eyed male.
a. What are the genotypes of the parents? ___________ & ________________
b. How many are white eyed, male___
c. How many are white eyed, female ___
d. How many are red eyed, male ____
e. How many are red eyed, female ____