3. Welsh corgis have cinnamon-colored faces. In some dogs, the cinnamon col the

Question

3. Welsh corgis have cinnamon-colored faces. In some dogs, the cinnamon col the chest, producing one of three pattems: a circle, a shield, or a triangle. Other dogs lack a pattern entirely and have no color on the chest. A male corgi with a triangle on his chest or continues onto (who came from a line of corgis who all had cinnamon-colored triangles for many generations) was mated with a female that had no color on her chest (who came from a line of corgis who all had no color on the chest for many generations). All of their adorable puppies had a cinnamon-colored shield on the chest. When the Fl offispring were intercrossed, they produced F2 puppies with the following phenotypes: 3 cinnamon-colored circle 6 cinnamon-colored shield 3 cinnamon-colored triangle 4 no color a. Color this corgi! (0.5 pt) b. Propose the mechanism(s) for inheritance of the chest pattern trait in corgis. (I pt) Using clearly-defined symbols, outline the cross from P to F2 for the corgis. Include the genotype for each phenotype described (2 pts) c.

Explanation / Answer

b. This ratio 3:6:3:4 comes in epistatis.

Expression of a gene or gene pair masks or modifies the expression of another gene or gene pair. So that that two gene pairs are interacting during the expression of the phenotype.

A - Triangle, B - circle AB - shield To express all the pattern another gene required that is the precursor for this all the patter that is H.

Both AH - Triangle, B H- circle ABH - shield . If Ah or Bh or ABh no pattern or color.

C. Parent     AA HH (Cinnamon Triangle) X BB hh (No color)

      F1                                           AB Hh (Cinnamon shield)

3 (AAHH or AAHh Triangle) : 6 (ABHH or ABHh shield) : 3 (BBHH or BBHh circle) : 4 (AAhh or BBhh No color)

AH Ah BH Bh AH AAHH Triangle AAHh Triangle ABHH shield ABHh shield Ah AAHh Triangle AAhh No color ABHh shield ABhh   No color BH ABHH shield ABHh shield BBHH circle BBHh circle Bh ABHh   shield ABhh   No color BBHh   circle BBhh    No color

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