Question

19. In a cross between a pure-breeding plant that produces tan lentils and a pure-breeding plant that produces gray lentils, all of the FI progeny plants produce brown lentils. When these are allowed to self-pollinate, the F2 plants are found to produce lentils in the following colors and ratios: F2 progeny: brown gray green tan 57 18 13 a. I poinl) What is the most likely phenotypic ratio being represented by the data above? b. (4 points) Prove (statistically) that your expected ratio is correct (/points) What are the genotypes of the two pure-breeding parental plants? c. (2 points) How is this example different from the type of cross that would typically produce this same phenotypic ratio? d. 13

Answer 1

ANS- The ratio represented by the phenotype is in the form of 3:1

As we count three from one group and one from other group.

Ans b - It is unable for me to describe statistically ratio. Hope you can find and get correct answer.

Ans c - A true breeding is a kind of breeding wherein the parents would produce offspring that would carry the same phenotype. This means that the parents are homozygous for every trait. ... With plants, true breeding occurs when plants produce only offspring of the same variety when they self-pollinate.

True breeding means that the parents will also pass down a specific phenotypic trait to their offspring.True bred organisms will have a pure genotype (genetic expression of a trait) and will only produce a certain phenotype. True bred is sometimes also called pure bred.

For Examples -
The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r). The round seed shape is dominant to the wrinkled seed shape. A true-breeding plant with round seeds would have a genotype of (RR) for that trait and a true-breeding plant with wrinkled seeds would have a genotype of (rr). When allowed to self-pollinate, the true-breeding plant with round seeds would produce only progeny with round seeds. The true-breeding plant with wrinkled seeds would only produce progeny with wrinkled seeds.

Cross-pollination between a true-breeding plant with round seeds and a true-breeding plant with wrinkled seeds (RR X rr) results in offspring (F1 generation) that are all heterozygous dominant for round seed shape (Rr).

Self-pollination in F1 generation plants (Rr X Rr) results in offspring (F2 generation) with a 3-to-1 ratio of round seeds to wrinkled seeds. Half of these plants would be heterozygous for round seed shape (Rr), 1/4 would be homozygous dominant for round seed shape (RR), and 1/4 would be homozygous recessive for wrinkled seed shape (rr).

ANS- d- Genotype refers the genes that an individual has. Phenotype refers to traits that an individual has, due to which genes are expressed and how. Two individuals could have the same genotype, but different phenotypes due to environmental factors influencing the expression of genes.