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Lecture

Genetic Practice Questions


Department
Biology
Course Code
BIOL 121
Professor
All

Page:
of 1
In cucumbers, thick spines on the stem (T) are dominant to fine spines (t) and
orange flowers (F) are dominant to white flowers (f). Pollen from a cucumber
with stems with thick spines and white flowers pollinates a cucumber with stems
with fine spines and orange flowers. The F1 all have thick spines and orange
flowers. The F1 are then crossed with cucumbers with fine spines and white
flowers (testcross).
a. When you perform the testcross, if the genes segregate independently, what
phenotypes do you expect and in what ratio do you expect these phenotypes to
occur? Show your work. (5 marks)
b. When you perform the testcross, if the genes are linked with no crossing over,
what phenotypes do you expect and in what ratio do you expect these
phenotypes to occur? Show your work. (5 marks)
c. What results do you expect from the testcross if the genes are linked and 20 map
units apart? Show all your work. (5 marks)