Download Punnett Square Practice

Punnett Square Practice
Name
Directions: Using the given Punnett Squares and spaces for identifying parent phenotypes, solve the following problems. Note: “Pure” = Homozygous; “Hybrid” = Heterozygous
Pictured below is an alien who displays all of the dominant characteristics of its species. Below is a chart listing various traits found in this alien race. Use the
information in the chart to solve the genetics problems that follow.
Trait
Dominant Phenotype
Recessive Phenotype
Body color
(Y) Yellow
(y) Orange
Number of Antennae
Eye color
Eyesight
Number of Body Rings
(A)
(P)
(E)
(R)
(a)
(p)
(e)
(r)
2
Purple
Glasses needed
3
1
White
Glasses not worn
5
1. A heterozygous male mates with a pure yellow female. What is the chance this
couple will produce an orange baby? __________________________
3. A heterozygous female with 3 body rings mates with a 5-ringed male. What is the
chance that this couple will have a baby that looks like its mother? ______________
2. Two purple-eyed aliens mate. Both aliens are hybrid for the eye color trait. What is
the chance this couple will produce a baby with a homozygous recessive genotype?
_______________________________________________________
4. A pure male alien displaying the dominant body color mates with a female that is
homozygous recessive for this characteristic. What is the chance that this couple will
have a baby with a hybrid genotype? ___________________________________
5. A male alien with 1 antenna mates with a female alien who has 2 antennae. The
female is heterozygous for the antenna trait. What is the chance that this couple will
produce a baby with the recessive phenotype? __________________________
6. An alien couple, both of which wear glasses, are having a baby. The male's genotype
is heterozygous. The female is phenotypically dominant but does carry the recessive
allele. What is the chance that this couple's baby will have to wear
glasses? __________________________________________
More Practice
A. In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A
kennel owner has a male dog that she wants to use for breeding purposes if
possible. The dog can hear, so the owner knows his genotype is either DD or
Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding
so that the deafness gene will not be passed on. This can be tested by breeding
the dog to a deaf female (dd). Draw the Punnett squares to illustrate these two
possible crosses. In each case, what percentage/how many of the offspring
would be expected to be hearing? Deaf? How could you tell the genotype of this
male dog? Also, using Punnett square(s), show how two hearing dogs could
produce deaf offspring.
B. In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a
genetic cross of two plants that are heterozygous for the seed shape trait, what
is the likelihood (probability) their first child will have spherical seeds? Their
second child? How do you know?
C. In sheep white is due to a dominant gene (W), black to its recessive allele
(w). A white ewe mated to a white ram produces a black lamb. If they produce
another offspring, could it be white? If so, what are the chances of it being
white? List the genotypes of all animals mentioned in this problem.
D. Woodrats are medium sized rodents with lots of interesting behaviors. You
may know of them as packrats. Let's assume that the allele of bringing home
shiny objects (H) is dominant to the allele 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? How many of
each phenotype?
7. A 3-ringed female mates with a homozygous male. The female has been genetically
tested and is carrying both the dominant and the recessive allele for this trait. The male
displays the recessive phenotype. What is the chance that this couple will have a
genetically pure baby? ________________________________
E. 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? What is the probability that a second
child won't be a tongue roller?