Question

Mendel's law of segregation predicts the following specific phenotypic ratios among the F, and Fa progeny from crosses between two pure-breeding parents for a single trait? A. F 1:0 F2 1:1 B. F1 1:0 F2 1:0 C. Fi 1:0 F2 3:1 D. F, 1:1 F2 3:1

Answer 1

Answer:

C. Fi 1:0, F2 3:1

Explanation:

Firstly, Mendel's law of segregation states that the alleles of a gene will randomly separate into gametes during gamete formation. In this case involving a single trait, hence, a single gene. Mendel crossed two purebreeding plants i.e. homozygous plants that produced different phenotypes for the same gene. He obtained his offsprings which he called F1 offsprings. He realized that all the F1 offsprings expressed only one phenotype. For example, when he crossed homozygous tall (TT) and short (tt) plants, he got F1 offsprings that were all tall.

He then self-crossed these F1 offsprings to produce a F2 offsprings that had a phenotypic ratio of 3:1 i.e. 3tall, 1short plant. He concluded that the alleles of the single gene had segregated into the gametes but one allele was capable of masking the expression of another, as seen in the heterozygous F1 offsprings that were all tall (Tt).

Hence, he obtained a 1:O ratio for his F1 offsprings then a 3:1 ratio for his F2 offsprings.