Dominant and recessive alleles

PrelimsCurrent affairs on this: Biology in news

Most genes come in two copies, one from each parent.

Two carrier parents

Two carriers
Each parent has one dominant and one recessive allele and shows no trait
Egg and sperm
Each parent passes on one of its two alleles, chosen at random
Four combinations
Two dominant; dominant and recessive, two ways; two recessive
The trait shows
Only the child with two recessive copies, one combination in four, expresses the trait

Two parents who show no trait can still have a child who does, because each can pass on the hidden recessive allele.Source: The Hindu, 18 June 2026

A dominant allele shows its effect with one copy; a recessive allele shows only when both copies are present.
A carrier has one recessive and one dominant allele and shows no trait.
When two carriers have a child, each may pass on the recessive allele, and a child with two copies expresses the trait; random shuffling of genes in egg and sperm formation decides this, which is why siblings differ.