Question

question 5
what are the expected phenotypic ratios for the f2 of a monohybrid and a dihybrid cross, respectvely?
a. 3:1 and 9:7
b. 3:1 and 1:2:1
c. 3:1 and 9:3:3:1
d. 1:2:1 and 9:3:3:1
question 6
in mendels dihybrid cross, a plant with yellow, round seed crossed to a plant with green, wrinkled seeds yields in f1 100% yellow, round seed.
if the f1 plants are allowed to self - pollinate, which proportion of the f2 offspring will be both green and round?
a. 1/3
b. 1/4
c. 3/16
d. 1/16
question 7
how many different types of gametes an individual with the genotype aabbccdd can make?
a. 1
b. 2
c. 4
d. 8
question 8
if we cross two individuals with the following genotypes: aabbcc x aabbcc, what is the probability that the offspring will also have the genotype aabbcc?
a. 50% (1/2)
b. 25% (1/4)
c. 12.5% (1/8)
d. 6.25% (1/16)

Explanation:

Question 5

Step1: Monohybrid cross F2 phenotypic ratio

For a monohybrid cross (e.g., \(Aa\times Aa\)), using Punnett - square analysis:

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$$

The phenotypic ratio (assuming \(A\) is dominant over \(a\)) is \(3\) (dominant phenotype: \(AA + Aa\)):\(1\) (recessive phenotype: \(aa\))

Step2: Dihybrid cross F2 phenotypic ratio

For a dihybrid cross (e.g., \(AaBb\times AaBb\)), using the Punnett - square or the formula \((3:1)\times(3:1)\) (based on the law of independent assortment).

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$$

The phenotypic ratio is \(9:3:3:1\)

Answer:

C. \(3:1\) and \(9:3:3:1\)

Question 6

Let \(Y\) (yellow) be dominant over \(y\) (green) and \(R\) (round) be dominant over \(r\) (wrinkled). The parental cross is \(YYRR\times yyrr\), and \(F_1\) is \(YyRr\). When \(YyRr\) self - pollinates (\(YyRr\times YyRr\)):
For the color trait (\(Yy\times Yy\)), the probability of \(yy\) (green) is \(\frac{1}{4}\) (from \(Yy\times Yy=(1YY:2Yy:1yy)\))
For the shape trait (\(Rr\times Rr\)), the probability of \(R -\) (round: \(RR + Rr\)) is \(\frac{3}{4}\) (from \(Rr\times Rr=(1RR:2Rr:1rr)\))
Using the multiplication rule of probability (since the two traits are independent according to Mendel's law of independent assortment), the probability of \(yyR -\) (green and round) is \(\frac{1}{4}\times\frac{3}{4}=\frac{3}{16}\)