Gene to phenotype Key Points
1. Describe the principal types of mutations mentioned in class to date and
what effects these can have on phenotype.
2. Explain how different mutations in a gene could affect the protein the gene
encodes at the transcriptional, translational, and post-translational levels.
3. Considering the aroma in rice example, explain how a loss of a function
mutation can lead to a gain of function phenotype (e.g. the recessive allele
confers aroma).
4. Compare the expected phenotypic ratios for F2, testcross and doubled
haploid progeny, where the parents are AA and aa and the A allele shows
incomplete dominance.
5. The following diagram illustrates DNA fragments of different sizes as
visualized via electrophoresis. Homozygous parental bands are shown. What
pattern do you expect to see for the F1, if these alleles show codominance?
P1
P2
F1
___
___
6. In many crops, F1 hybrids are very popular because they show hybrid vigor.
Explain how hybrid vigor and overdominance could be related.
7. Consider the cyanide in clover example. Using the same genotypes for the
parents and F1 as shown in the notes, what phenotypic ratio would you
expect if you produced doubled haploids rather than an F2 generation?
8. In the vernalization example shown in the notes, what is the role of the
environment in determining flowering time in the following two scenarios?
a. VRNH2 is present and there is a binding site in the first intron of
VRNH1
b. VRNH2 is deleted and there is a binding site in the first intron of
VRNH1
9. Consider the slide in the class notes showing the few barley plants that
flowered in trays of plants that did not flower, and the corresponding gel
electrophoresis pictures. Assume you have a job detecting contaminants in
seed shipments. Your employer is ready to ship 10 tons of seed of a variety
that requires vernalization. Barley varieties that do not require vernalization
will flower ~ 30 days after planting.
a. You have 1 week to test that the seed shipment is contaminated with
seed of a variety that does not require vernalization. Would you use
growth in trays or electrophoresis as a measure of the %
contamination?
b. If you had 2 months to determine the % contamination, would you
choose growth in trays or electrophoresis as a measure of the %
contamination? If you had 2 months, would there be any advantage to
using both techniques?
10. Carefully review the “Reminders from the first lecture” series of slides and
reflect upon what you have learned to date…..