What kinds of gametes will be produced by a pea plant with yellow round seeds that has the genotype YyRr?

Answer

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Hint: Pea plant is used to study genetics by Mendel. He considered seven characters of the pea plant and crossed them in different possible ways and obtained various generations. Dihybrid crosses are those where the two-parent selected for crossing differs in two characters from each other.

Complete answer:
A pea plant with yellow round seeds is crossed with another plant with green wrinkled seeds. The genotype of yellow round seeds is YYRR and the genotype of green wrinkled seeds is yyrr. In the ${F_1}$ generation, the progenies obtained are heterozygous yellow round since yellow and round are dominant characters. The ${F_1}$ generation will be YyRr (Yellow round). Later the ${F_1}$ progeny are self-fertilized and ${F_2}$ progeny are obtained. The ratio of progeny is 9:3:3:1.

The phenotype of ${F_2}$ generation is – Yellow round, Yellow wrinkled, Green round, Green wrinkled and the phenotypic ratio of ${F_2}$ generation is 9:3:3:1 respectively.
According to the question, there are 320 plants produced in the ${F_2}$ generation. The phenotype of the ${F_2}$ generation will be Yellow round, Yellow wrinkled, Green round, Green wrinkled.
Yellow and wrinkled seeds- In the ${F_2}$ generation, the ratio of yellow wrinkled seeds formed is 3. Out of 320 plants, the total number of yellow wrinkled seeds formed will be 60 plants that are yellow wrinkled.
Yellow round seeds- In the ${F_2}$ generation, the ratio of yellow round seeds formed is 9. Out of 320 plants, the total number of yellow round seeds formed will be 180 plants are yellow round.
Green and round seeds – In the ${F_2}$ generation the ratio of green and round seeds formed is 3. Out of 320 plants, the total number of green round seeds formed will be 60 plants are green round.
Green and wrinkled seeds- In ${F_2}$ generation the ratio of green and wrinkled seeds formed is 1. Out of 320 plants, the total number of green wrinkled seeds formed will be 20 plants that are green wrinkled.

So, the correct answer is option B.

Note:
Phenotypic character is the set of the observable characteristics of an organism. Genotypic character is an organism set of heritable genes passed from parents to offspring.

    Given the principles revealed in a monohybrid cross, Mendel hypothesized that the result of two characters segregating simultaneously (a dihybrid cross) would be the product of their independent occurrence. Consider two characters, seed color and seed shape. As previously shown, Y dominates y to determine seed color, and R factor for "round" dominates the r factor for  "wrinkled" to determine seed shape. He then proceeded to test his hypothesis experimentally.

    The P (Parental) cross is between true-breeding lines of wrinkled yellow peas (rrYY) and round green peas (RRyy). The F1 offspring are therefore all RrYy, and are all round and yellow. In forming the F2 plants, the alleles at the two loci segregate independently. That is, the chance of getting an R allele and a Y allele is 1/2 x 1/2, of getting an R and a y 1/2 x 1/2, and so on. Thus, all four possible diallelic combinations occur with an equal probability of 1/4. The same is true for both parents. Given four possible gamete types in each parent, there are 

    Alternatively, recall that the phenotypic ratio expected for either character is 3:1, either 3 "Y" : 1 "y", or 3 "R" : 1 "R". Then, the expected phenotypic ratios of the two traits together can be calculated algebraically as a

(3Y + 1y) x (3R + 1r) = 9YR + 3Yr + 3Ry + 1 ry

    To predict the genotypic ratios, recall that for each gene the ratio is 1 : 2 : 1 :: AA : Aa : aa . Then, algebraically

(1YY + 2Yy + 1yy) x (1RR + 2Rr + 1rr) = 1 YYRR + 2 YYRr + 1 YYrr + 2YyRR + 4YyRr + 2 Yyrr + 1yyRR + 2yyRr + 1yyrr

    That is, we expect a characteristic 1:2:1:2:4:2:1:2:1 ratio of the nine possible genotypes. These nine genotypes can be grouped into four phenotypes, for example 1 YYRR + 2 YYRr + 2 YyRR + 4 YyRr = 9Y-R- round, yellow peas. The ratio of these phenotypes is of course9:3:3:1.

    Mendel reported the results of some but not all of the "7 choose 2" = (7)(7-1)/(2) = 21 possible dihybrid crosses

with seven characters. He performed several trihybrid crosses as well.

:

(1) Repeat the analysis above with a cross of RRYY x rryy.

(2) Predict the phenotypic and genotypic ratios of a

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