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Name:_______________
A) Homozygous means the _____________________________________________
B) Definition of phenotype:_____________________________________________
C) Explain what an allele is by using an example with eyes.
_______________________________________________________________________
_______________________________________________________________________
D) Complete the following punnett square below.
E) Cross a short pea plant (t) with one that is heterozygous for tallness (T):
F) In seals, the gene for the length of the whiskers has two alleles. The dominant allele
(W) codes long whiskers & the recessive allele (w) codes for short whiskers.
1) What percentage of offspring would be expected to be true breeds for whiskers from the
cross of two long-whiskered seals, one that is homozygous dominant and one that is
heterozygous?_________ Draw out the punnet square!
2) If one parent seal is pure long-whiskered and the other is short-whiskered, what percent of
offspring would have short whiskers?_________ Draw out the punnet square! What are the
genotype(s) that are possible in the offspring?_______________________________.
G) In purple people eaters, one-horn is dominant (H) while no horn is a recessive (h) trait. Draw
a Punnet Square showing the cross of a purple people eater that is a pure breed for horns with
a purple people eater that is homozygous for no horns.
What are the genotypes?____________________________________________________
What are the phenotypes? ___________________________________________________
What is the probability of having no horned purple people eaters? _________%
Or
What is the chance of having a horned purple people eater? ______ out of ______
H) Predict the probability that a red cow would have a black calf, if the father was
Heterozygous for the trait. Black is the dominant trait (B) and red (b) is recessive.
Daddy Cow
Mommy Cow
Genotype:
Genotype:
Offspring
("F1" Generation)
Percentages & Probability
Genotypes:
Phenotype:
Phenotype:
Phenotypes:
The probability of having a black calf is ______ out of ______ or ______%
I) In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a browneyed woman and they have three children, two of whom are brown-eyed and one of whom is
blue-eyed. Draw the Punnett square that illustrates this marriage.
1) What must the woman’s genotype be?
2) If the above is her genotype, what are the two alleles that she can give?
3) If the man has brown eyes, but has a blue-eyed child what must his genotype be?
4) If that’s his genotype, what are the two alleles that he can give?
J) What is the definition of a genotype?________________________________________
_______________________________________________________________________
K) Heterozygous means_____________________________________________________
L) THE CHALLENGE! You have learned a lot of terms along with how to use a punnet square.
So far all you have had to do is mess with one specific gene. Try and see if you can complete
this table! Let’s look at the probabilities of a plant being tall(T) or short(t), and purple(P) or
white(p). You are crossing a heterozygous tall and heterozygous purple plant with a true breed
tall and white plant. First you will have to figure out the different combinations of each plant,
then fill in the table. I have started you off…
T P
T p
t P
t p