Experiment 19 — Mendel’s Peas

Topic: Biology · Class 10 · Heredity: monohybrid cross and the Punnett square

Aim: Cross two heterozygous tall plants (Tt × Tt) and obtain the 3 : 1 ratio.

Daily: Plant breeders use exactly this arithmetic to develop disease-resistant wheat, and genetic counsellors use it to explain the chances of inherited conditions.

Question: Two tall pea plants (Tt) are crossed. What fraction of the offspring will be dwarf?

Exp: Only tt is dwarf, and that occurs in one of four combinations.

Question: A Tt plant is tall because T is…

Exp: One dominant allele is enough to show the trait.

Question: The genotypic ratio from Tt × Tt is…

Question: A dihybrid cross of two heterozygotes gives a ratio of…

Exp: Traits assort independently.

Question: The sex of a human child is determined by…

Exp: The mother always contributes an X chromosome.