Question

3. While practicing social distancing, it’s good to still go outside for a walk, bike ride, or observing nature. While going on a walk and making sure there is always at least 6 ft between you and others, you discover a new tree. In fact, you discover a whole forest of this tree that grows ICE CREAM. Some trees grow pistachio ice cream, and others grow chocolate peanut butter ice cream (to clarify, I mean chocolate ice cream with peanut butter in it… clearly superior to any vanilla with Reese’s mixed in). Some grow giant scoops of ice cream, and others grow small scoops of ice cream. You can’t wait to capitalize on your discovery and start a farm of ice cream trees. But first, you want to figure out how the alleles for the ice cream flavor gene and the scoop size gene are inherited so that you can try to grow large scoops of both flavors of ice cream. You figure out, by performing many crosses, that the chocolate peanut butter allele is dominant and the pistachio allele is recessive. You also find that the large scoop allele is dominant and the small scoop allele is recessive. Now you want to figure out if the flavor gene and the scoop size gene are autosomally linked, or autosomally not-linked. You decide to cross a tree that is homozygous dominant for both flavor and scoop size to a pistachio tree with small scoops. Use F/f for flavor and S/s for scoop size.

a. What are the genotypes of the two trees in the parental generation? (2 points)

b. Draw a Punnett square to indicate what the F2 generation would be if the genes are autosomal linked.

c. Draw a Punnett square to indicate what the F2 generation would be if the genes are autosomal not linked.

d. Your F1 trees produce 100 offspring. 75 of them are chocolate peanut butter trees with large scoops of ice cream. 25 of them are pistachio trees with small scoops. What mode of inheritance do you think is controlling flavor and scoop size, and why? (1 point for correct mode of inheritance, 1 point for explanation).

Answer 1