You self-pollinate a pea plant that is heterozygous for round/wrinkled alleles a

Question

You self-pollinate a pea plant that is heterozygous for round/wrinkled alleles at the r locus (Rr). You want to figure out the probability of finding 2 round and 4 wrinkled seeds in a 6-seed pod, Round is dominant to wrinkled, so Rr plants are round. A in an F_2 monohybrid cross like this, what proportion of the progeny will be round (p) and what proportion of the progeny will be wrinkled (q)? p= q= Using Pascal's triangle to identify the coefficients for each possible outcome write out all possible outcomes with their coefficients, and summing all to a value of 1. DO NOT FILL IN the values for p and q in this answer. Identify the outcome that corresponds to 2 round and 4 wrinkled seeds in a 6-seed pod and write It below (being sure to include the coefficient). Show how you would calculate the probability of obtaining this result (2 round and 4 wrinkled seeds in a 6-seed pod). In other words, insert the values for p and q and show how you would (add/subtract/multiply/divide) them to come up with the probability of this outcome. Do not do the math. (Example of the format you should use in your answer: 10 x 1/2 x 1/2 x 1/2 or 10 x 0.5 x 0.5 x 0.5)

Explanation / Answer

You self-pollinate a pea plant that is heterozygous for round/wrinkled alleles at the r locus (Rr). You want to figure out the probability of finding 2 round and 4 wrinkled seeds in a 6 seed pod, Round is dominant to wrinkled, so Rr plants are round. Ar in an Fa monohybrid cross like this,

what proportion of the progeny will be round (p) and what proportion of the progeny will be wrinkled (q)? Note: p q B. Using Pascal's triangle to identify the coefficients for each possible outcome (hint: p means 6 round peas in a pod),

R---------round --------dominant allele

Recessive allele ---r--------wrinkled

Rr x Rr

R

r

R

round Rr

round Rr

r

round Rr

wrinkled rr

Probability of round seed= ¾=0.75---------------p

Probability of wrinkled seed= 1/4=0.25-----------q

of finding 2 round and 4 wrinkled seeds in a 6 seed pod,

n=6

(p+q)^n=

(p+q)^6=p^6+ 6p^5q^1+15p^4q^2+20p^3q^3+15p^2q^4+6p^1q^5+q^6=

=15p^2q^4 = 2 round and 4 wrinkled

=15*0.75^2*0.25^4 =0.0329—answer

Coefficient

p^6

1

Six round

6p^5q^1

6

5 round and 1 wrinkled

15p^4q^2

15

4 round and 2 wrinkled

20p^3q^3

20

3 round and 3 wrinkled

15p^2q^4

15

2 round and 4 wrinkled

6p^1q^5

6

1 round and 5 wrinkled

q^6

1

6 wrinkled

R

r

R

round Rr

round Rr

r

round Rr

wrinkled rr

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