Question

Given above is a schematic representation of the inheritance of a certain feature of seeds of a garden pea. Study it carefully and answer the questions that follow: What are dominant and recessive alleles of this trait?

Accepted Answer

Dominant refers to the relationship between two versions of a gene. Individuals receive two versions of each gene, known as alleles, from each parent. If the alleles of a gene are different, one allele will be expressed; it is the dominant gene. The effect of the other allele, called recessive, is masked. Peas had been shown to be true-breeding. During Mendel’s pea experiments, he noted that some varieties of peas had round seeds, while others had irregular wrinkled seeds. A pea plant that has round seeds has the genotype Rr. It is crossed with a pea plant that has wrinkled seeds and the genotype rr. As a result of crossing these two pea variants, Mendel discovered that the round-seeded and wrinkled-seeded traits were two facets of the same character, suggesting to modern plant scientists that a single gene determines whether seeds are round or wrinkled. Here, RR - genotype for round pea seeds which is dominant and rr - genotype for wrinkled seeds which is recessive. A monohybrid cross results in a phenotypic ratio of $3 : 1$ (dominant to recessive), and a genotypic ratio of $1 : 2 : 1$ (homozygous dominant to heterozygous to homozygous recessive).

Given above is a schematic representation of the inheritance of a certain feature of seeds of a garden pea. Study it carefully and answer the questions that follow: What are dominant and recessive alleles of this trait?

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