Bio 304 Genetics Exam Page 3

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21. Consider the following piece of messenger RNA and respond to each question (3 pts. each):
5´-GGGCAGCAAUACUUUUAA-3´
a) Draw both strands of the segment of DNA from which this mRNA was transcribed, and
identify the ends of each strand.
3’-CCCG TCG T TATGAAAATT-5’
5´-GGGCAGCAAT ACT T TTAA-3´
b) Indicate which of the DNA strands served as template for RNA synthesis.
upper
c) Using the codon chart, give the amino acid sequence of the protein that would be
produced by translation of the mRNA, assuming that he ribosome moved along the
mRNA from left to right, beginning with the leftmost nucleotide.
GlyGlnGlnTyrPhe(STOP)
d) Label the amino and carboxyl ends of this amino acid chain.
amino left, carboxyl right
22. A plant is heterozygous Aa Bb at two unlinked genes. Answer each of the following: (4
points each)
8 FREE POINTS
a) For a given pollen grain, what is the probability that it is A b?
½ X ½ = ¼
b) If the plant is allowed to self-pollinate, what proportion of seeds do you expect to be
Aa Bb?
chance of Aa = ½; chance of Bb = ½; chance of Aa Bb = ½ X ½ = ¼
23. Barley is a self-fertilizing plant that can be cross-fertilized and you are given two strains with
pale green leaves. In strain A, the trait is caused by a chloroplast gene; in strain B, the trait is
caused by a recessive nuclear gene. Predict the phenotypes and proportions that will result
from the following crosses: (2 points each)
a) strain A egg with strain B pollen.
All pale (maternal effect)
b) strain B egg with pollen from the zygote resulting from the previous cross (a)
Bb X Bb → ½ pale, ½ dark (chloroplast pale gene in pollen will not affect progeny)
c) strain B egg with strain B pollen.
bb X bb → all pale

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