Question

a plant that has round and yellow seeds (rryy) is crossed with a plant that has round and yellow seeds (rryy). what is the ratio of the offspring that will have round and yellow seeds? key: r = round, r = wrinkled, y = yellow, y = green. 1:16 3:16 8:16 9:16

Explanation:

Step1: Determine gametes

The plant with genotype RrYy can produce 4 types of gametes: RY, Ry, rY, ry in equal proportions. When two RrYy plants are crossed, we use a Punnett - square analysis. But we can also use the product rule of probability.

Step2: Analyze the probability of each trait

For the seed - shape trait (R = round, r = wrinkled), the probability of getting a round - seeded offspring (RR or Rr) from the cross Rr×Rr is $\frac{3}{4}$ (RR:Rr:rr = 1:2:1). For the seed - color trait (Y = yellow, y = green), the probability of getting a yellow - seeded offspring (YY or Yy) from the cross Yy×Yy is $\frac{3}{4}$ (YY:Yy:yy = 1:2:1).

Step3: Calculate the probability of round and yellow offspring

Using the product rule of independent events (since the two traits assort independently according to Mendel's law of independent assortment), the probability of getting an offspring with round and yellow seeds is the product of the probabilities of getting round seeds and yellow seeds. So, $P=\frac{3}{4}\times\frac{3}{4}=\frac{9}{16}$.

Answer:

$\frac{9}{16}$