3 Factor Crosses
Show all work on a separate sheet of paper!!
1. Which of Mendel’s postulates can only be demonstrated in crosses involving at least two pairs of traits?
Define it.
2. How many different types of gametes can be formed by individuals of the following genotypes:
a. AaBb
b. AaBB
c. AaBbcc
d. AaBBcc
e. AaBbCc
f. AaBbCcDdEd
3. Using the branched diagram (forked line method), determine the phenotypic ratios of the following
crosses:
a. AaBbCc x aaBBCc
b. AaBBCc x aaBBCc
c. Test cross of AaBbCc
4. Purple, green spotted dinos are dominant over plain pink dinos. A yellow star marking on the forehead is
recessive to a red star marking.
a. Assign letters to the three traits.
b. Complete the following cross: A hybrid dino is crossed with a dino that is also hybrid for the
above traits.
c. Probability that the offspring from the cross in problem b will be pink and unspotted with a
yellow star marking?
d. Probability that the offspring from cross in problem b will be purple, spotted and have a yellow
star marking?
e. Chance their offspring (from b) will be spotted?
f. Pink, green spotted dinos are shunned. What is the probability that a hybrid dino and a dino that
is recessive for all traits would produce such and outcast?
g. Draw the offspring(s) of the following cross: homozygous purple, spotted, yellow star dino
crossed with a heterozygous purple and spotted with a red star*. Show work leading to F1
generation.
*note: homozygous for red star. Neatness & creativity count!!