Question
(a) What is a monohybrid cross? (b) Explain the law of Mendel with the help of a monohybrid cross.
Or,
Give an example of a monohybrid cross and explain it.
Or,
How did Mendel explain the occurrence of tallness of all plants in the F₁ generation in his experiment of Monohybrid cross? Discuss in brief how did he also explain the occurrence of growing tall and dwarf pea plants in the ratio of 3: 1 in the F2 generation in the same experiment. Mention the genotypic ratio obtained in the F2 generation of the same cross.
Answer
(a) A monohybrid cross is a type of genetic cross in which a single trait is being studied. It involves the mating of two individuals that are heterozygous for the trait of interest, resulting in the offspring being produced with a 3:1 ratio of dominant to recessive phenotypes.
(b) Mendel’s law of segregation states that each individual has two alleles for each trait, and these alleles separate during gamete formation so that each gamete receives only one allele. The law was derived from Mendel’s monohybrid cross experiment, where he crossed purebred tall and purebred dwarf pea plants. He found that the offspring produced in the F1 generation were all tall, indicating that the tall trait was dominant. However, in the F2 generation, the ratio of tall to dwarf plants was 3:1, suggesting that the trait was determined by two factors (later termed alleles) and that the recessive allele only appeared in plants that inherited two copies of it. This demonstrated the principle of segregation, where the alleles of a gene separate during gamete formation, with each gamete receiving only one allele, which is randomly determined.
