A) Create the Punnett Square for This Cross

MONOHYBRID CROSS PRACTICE

1.  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 is controlled by a single gene and is dominant to the trait of carrying home only dull objects. Suppose two heterozygous individuals are crossed.

a)  Create the punnett square for this cross.

b)  What is the genotype ratio of the offspring?

c)  What is the probability that a woodrat born to this couple will have the trait of bringing home shiny objects?

2.  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 are controlled by a single gene with arms of the same length being dominant to arms of different lengths.

a)  What is the genotype of your cactus?

b)  Create the punnett square if you bred your cactus with one that is homozygous dominant.

c)  What is the probability of the offspring of this cross having arms of different lengths?

3.  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 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.

a)  What is the male's genotype?

b)  Create the punnett square for this cross.

c)  What is the phenotype ratio of the offspring?

4.  A woman who has a heterozygous genotype for tongue rolling marries a man who cannot roll his tongue.

a)  Is tongue rolling dominant or recessive?

b)  The first child of the couple above has his father's phenotype. What are the genotypes of the mother, father, and child?

c)  Create the punnett square for this cross.

d)  What is the probability that the next child born will share his older brother’s trait?

5.  Match each of the following genetic terms to the correct example:

Genetic Vocabulary / Examples
____1. Genotype / T) RR
____2. Phenotype / U) 4Ee : 0 ee and EE
____3. Allele / V) Short-big-toe
____4. Gametes / W) 3/4
____5. Genotype Ratio / X) 2 brown eyes: 2 blue eyes
____6. Phenotype Ratio / Y) Gg à G or g
____7. Probability / Z) f