Download GENETICS PROBLEMS

GENETICS PROBLEMS
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How do we solve genetics problems?
CODOMINANT TYPE INHERITANCE
In codominant type inheritance, there is NOT a purely dominant gene and a purely recessive gene. We no
longer have to use CAPITAL letters or lower case letters because we are not worried about DOMINANT or
RECESSIVE. We still figure out the genotypes of all the individuals involved, however now when they are
HETEROZYGOUS we see a mixed trait (mixed between the two extremes). Then we do a punnett square to
finish the problem.
For each of the problems below, you need to complete the following pieces. A.) Assign the letters to the genes,
B.) Write out the genotypes of the parents that are to be crossed/mated, C.) Do the punnett square, D.) Write
out all of the possible genotypes and the chances that each of the genotypes might happen, E.) Write out all of
the possible phenotypes and the chances that each of the phenotypes might happen.
Example:
In Labrador Retrievers (a type of dog), neither yellow coat or black coat are dominant. They blend to form a
chocolate colored coat. Cross two chocolate colored labs.
A.
B.
Y = Yellow
B = Black
YB = Chocolate
X
C.
Y
Y
YY
B
D.
YB
E.
B
YB
BB
__ __ = ¼ or 25%
__ __ = 2/4 or 50%
__ __ = ¼ or 25%
= ¼ or 25%
= ¼ or 25%
= 2/4 or 50%
Problems
1. Using the information in the example above, cross a Yellow Lab with a Black lab.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
2. Using those same traits, cross a Yellow Lab with a Chocolate Lab.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
3. Prove that you can get a Yellow lab as an offspring without having a Yellow lab as a PARENT.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
4. In pea plant flowers, Red flowers and White flowers are codominant and blend to form pink flowers. Cross a
white flower plant with a red flower plant.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
5. Using the traits in #4, cross two pink flowers.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
6. Using those same traits in #4 & 5, cross a White with a pink.
A. ________________ C.
D.
__________________
__________________
B. ________________
E.
__________________
__________________
7. What two flowers can we cross to have a chance to get a red flower, without having a red flower as a parent?
8. Can we get a white flower from crossing a Red flower with a pink flower? Explain.