Question

16 in cattle, roan coat color (mixed red and white hairs) occurs in the nonmatching (rw) offspring of matching red (rr) and matching white (ww). which of the following crosses would produce offspring in the ratio of 1 red: 2 roan: 1 white? (aks 7e1) a red (rr) x roan (rw) b roan (rw) x roan (rw) c white (ww) x roan (rw) d red (rr) x white (ww)

Explanation:

Step1: Analyze Option A (RR x RW)

When crossing RR (red) with RW (roan), the possible offspring genotypes are RR (from R of RR and R of RW) and RW (from R of RR and W of RW). So the ratio is 1 red (RR) : 1 roan (RW), not 1:2:1.

Step2: Analyze Option B (RW x RW)

Using a Punnett square for RW x RW:

	R	W
W	RW	WW

The genotypes are RR (red), RW (roan), RW (roan), WW (white). So the ratio is 1 RR (red) : 2 RW (roan) : 1 WW (white), which matches the required ratio.

Step3: Analyze Option C (WW x RW)

Crossing WW (white) with RW (roan), the possible offspring are RW (roan) and WW (white). The ratio is 1 roan : 1 white, not 1:2:1.

Step4: Analyze Option D (RR x WW)

Crossing RR (red) with WW (white), all offspring are RW (roan). So the ratio is all roan, not 1:2:1.

Answer:

B. Roan (RW) x Roan (RW)