Biology · Inheritance. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Inheritance is the passing of genetic information from one generation to the next. A gene can exist in different forms called alleles. Each body cell has two alleles of a gene, one from each parent. Each gamete carries only one.
The genotype is the pair of alleles (TT, Tt or tt). The phenotype is the feature you can observe (tall or short). A dominant allele shows whenever it is present. A recessive allele shows only when there are two copies.
A genetic diagram or Punnett square shows which gametes each parent makes and how they can combine. It gives probabilities, not exact numbers, so real results with few offspring often differ from the expected ratio.
Students think earlier children change the chances for the next child. Every fertilisation is a separate event, so the probability is the same each time.
Answer: 1 group A : 1 group B. No child can be group AB or group O.
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