Buffyyour study buddyHi! Ask me about dominant/recessive traits, Punnett squares, or sex determination.
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Why you look a bit like your parents — and a bit like no one. Mendel's peas, dominant and recessive traits, and the genetics of boy-or-girl, all on a grid you can fill yourself.
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Heredity is the passing of traits from parents to offspring through genes. Variation is the differences between individuals — created mainly during sexual reproduction. Variation is the raw material that helps a species survive changing conditions.
Mendel crossed pea plants and found that one form of a trait (the dominant, T) masks the other (the recessive, t). Crossing two hybrids (Tt × Tt) gives a 3:1 ratio of tall to short. Build the cross on a Punnett square:
When two traits are followed together (e.g. seed shape and colour), they are inherited independently. A dihybrid cross of two double-hybrids gives the famous 9 : 3 : 3 : 1 ratio in F₂ — proving the two traits sort separately.
Genes sit on chromosomes (made of DNA). Different versions of a gene are alleles (T and t). The combination an organism carries is its genotype (e.g. Tt); the trait you actually see is its phenotype (e.g. tall). One dominant allele is enough to show the dominant trait.
Humans have a pair of sex chromosomes: females are XX, males are XY. The mother always passes an X; the father passes X or Y — so the father determines the sex of the child.
Result: 50% girl (XX) and 50% boy (XY). The father\u2019s sperm (X or Y) decides — never the mother.
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Modelled on CBSE's competency-based pattern — MCQ, assertion–reason and case-study items, the kind that now make up about half your board paper.
Interactive explainers inspired by OpenMAIC (THU-MAIC, MIT-licensed). Content from NCERT Class 10 Science.
Buffyyour study buddyBuffy is an AI helper and can be wrong — always check your NCERT textbook.