Name: ______Date: ______Period: ______Monohybrid & Dihybrid Cross Review worksheet #4 Cook
Monohybrid crosses The following problems can be found at this interactive website: http://www.ksu.edu/biology/pob/genetics/mono.htm For more practice, go to this website. You can choose hints and go through the problems step-by-step.
1. In dogs, wire hair (S) is dominant to smooth (s). In a cross of a homozygous wire-haired dog
with a smooth-haired dog, what will be the phenotype of the F1 generation? ______
What would be the genotype? ______
What would be the ratio of wire-haired to smooth-haired dogs in the F2 generation ? ______
F1 F2
2. Woodrats are medium sized rodents with lots of interesting behaviors. You may know of them as packrats. Let's assume that the trait of bringing home shiny objects (H) is controlled by a single locus gene and is dominant to the trait of carrying home only dull objects (h). Suppose two heterozygous individuals are crossed. How many of each genotype would be expected if only 4 offspring were produced?
HH ______Hh ______hh ______
How many of each phenotype? Bring home shiny objects ______
Brings home dull objects ______
1 Name: ______Date: ______Period: ______Monohybrid & Dihybrid Cross Review worksheet #4 Cook
3. Saguaro cacti are very tall cylindrical plants that usually have two L- shaped arms, one on each side. Suppose you lived in southern Arizona where the Saguaro cactus is common and you happen to have one growing in your yard. Your Saguaro has two arms but one is longer than the other. Now, assume that arm length in these cacti is controlled by a single gene with arms of the same length (A) being dominant to arms of different lengths. What is the genotype of your cactus? ______
Could one of the parents of your cactus have had a phenotype with arms the same length? ______
If so, what would have been the genotype of that parent?
______
Suppose you cross your cactus with that of your neighbor which has arms of the same length. Your great grandchildren it takes a Saguaro cactus a long time to mature) find that half of the resulting offspring have arms the same length & half have arms of different lengths. What was the genotype of your neighbor's cactus?
______
4. The common grackle is a species of robin-sized blackbirds that are fairly common (hence the name) over most of the United States. Suppose that long tails (L) were dominant to short tails in these birds. A female short-tailed grackle mates with a male long-tailed grackle who had one parent with a long tail and one parent with a short tail. What is the male's genotype?
______How many of each genotype will be found in the
F1 generation (assume 4 offspring)?
LL ______Ll ______ll ______
How many of each phenotype will be found in the F1 generation?
Long tail: ______Short tail: ______
2 Name: ______Date: ______Period: ______Monohybrid & Dihybrid Cross Review worksheet #4 Cook
5. The ability to curl your tongue up on the sides (T, tongue rolling) is dominant to not being able to roll your tongue. A woman who can roll her tongue marries a man who cannot. Their first child has his father's phenotype. What are the genotypes of the mother, father, and child?
Mother ______Father ______Child ______
What is the probability that a second child won't be a tongue roller? ______
Dihybrid crosses The following problems can be found at this interactive website: http://www.ksu.edu/biology/pob/genetics/intro.htm Click on the dihybrid crosses link. Answer the questions listed. You can choose hints and go through the problems step-by-step.
1) About 70% of Americans perceive a bitter taste from the chemical phenylthiocarbamide (PTC). The ability to taste this chemical results from a dominant allele (T) and not being able to taste PTC is the result of having two recessive alleles (t). Albinism is a trait with normal pigment being dominant (A) and the lack of pigment being recessive (a). A normally pigmented woman who cannot taste PTC has a father who is an albino taster. She marries a homozygous, normally pigmented man who is a taster but who has a mother that does not taste PTC.
What are the genotypes of the possible children? ______
What percentage of the children will be albinos? ______
What percentage of the children will be non-tasters of PTC? ______
3 Name: ______Date: ______Period: ______Monohybrid & Dihybrid Cross Review worksheet #4 Cook
2) Wolves are sometimes observed to have black coats and blue eyes. Assume that these traits are controlled by single locus genes and are located on different chromosomes. Assume further that normal coat color (N) is dominant to black (n) and brown eyes (B) are dominant to blue (b). Suppose the alpha male and alpha female of a pack (these are the dominant individuals who do most of the breeding) are black with blue eyes and normal colored with brown eyes, respectively. The female is also heterozygous for both traits.
How many of the offspring (assume 16) living in the pack will have each of the following genotypes?
NNBB ______NNBb ______NNbb ______
NnBB ______NnBb ______Nnbb ______nnBB ______nnBb ______nnbb ______
What percent of the offspring will be normal colored with blue eyes? ______
One more just for fun……
3) In cookie monsters, blue fur is codominant over green fur. The gene loving chocolate chip cookies is dominant over the gene loving oatmeal raisin cookies. Mr. Cookie Monster is a heterozygous blue oatmeal raisin eating cookie monster and Mrs. Cookie Monster is a green homozygous chocolate chip eating cookie monster. They are expecting baby monsters! Show the Punnett square, parents’ genotypes and list the phenotypes of the offspring.
parents’ genotypes ______
phenotypes of the offspring
______
What kind of cookies should you buy for their offspring?
4 Name: ______Date: ______Period: ______Monohybrid & Dihybrid Cross Review worksheet #4 Cook
______
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