What is the difference between dominant and recessive alleles? Give a human example.

Alleles are different versions of a gene. Dominant allele (capital letter, e.g., A): expressed even with just one copy (in Aa). Recessive allele (small letter, e.g., a): only expressed when two copies present (in aa). Human example — tongue rolling: R (rolling) is dominant, r (non-rolling) is recessive. RR = roller. Rr = roller (R dominates). rr = non-roller. Another example — earlobe attachment: free earlobe (F) dominant over attached (f). For NEET genetics problems, always write out Punnett squares. The phenotype (what you see) is determined by the dominant allele, but the genotype (genetic makeup) carries both alleles. Carriers (Aa) have the dominant phenotype but carry a recessive allele they can pass on.