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Dominant and recessive epistasis

My teacher gave me a question to work through and I incurred some confusion that she wasn't able to fully clarify.

The question gave a gene with two alleles, A and a, which determine the colour of the coat in mice.

AA or Aa is Albino fur and aa is black fur.

We are then told that these colours can only be expressed in the presence of at least one dominant allele of the gene C/c. Otherwise, the fur will be Agouti in the case of cc.

Crossing aaCC with AAcc gives an F1 generation of AaCc.

However, for the F2 generation (crossing AaCc with AaCc), the phenotypic ratio is 9:3:4.

This is what has confused me, because this ratio occurs in recessive epistasis. But is this not dominant epistasis?

Thanks!

(edited 8 years ago)

Reply 1

Serine Soul

My friend messaged me with a similar question just the other day...

When you initially crossed aaCC and AAcc, did you use the combinations AC, Ac, aC, ac as your gamete sets of alleles?

Reply 2

crashMATHS

Original post by enaayrah

My friend messaged me with a similar question just the other day...

When you initially crossed aaCC and AAcc, did you use the combinations AC, Ac, aC, ac as your gametes?

Indeed

Reply 3

crashMATHS

Original post by enaayrah

My friend messaged me with a similar question just the other day...

When you initially crossed aaCC and AAcc, did you use the combinations AC, Ac, aC, ac as your gamete sets of alleles?

Oh I think I've got it now.

It is recessive epistasis, because the gene C/c must be cc in order to mask the production of the colour pigment.

Is that right?

Reply 4

Serine Soul

Original post by kingaaran

Indeed

Hmm then I have no clue :redface:

I hope someone comes and clears this up for you

Reply 5

Serine Soul

Original post by kingaaran

Oh I think I've got it now.

It is recessive epistasis, because the gene C/c must be cc in order to mask the production of the colour pigment.

Is that right?