Dominance and Recessiveness in Alleles — NEET Biology
✅ Asked in NEET 2016As Mendel found the phenotype of the F1 heterozygote Tt to be exactly like the TT parent in appearance, he proposed that in a pair of dissimilar factors, one dominates the other (as in the F1) and hence is called the dominant factor while the other factor is recessive. In this case T (for tallness) is dominant over t (for dwarfness), that is recessive. He observed identical behaviour for all the other characters/trait-pairs that he studied. It is convenient (and logical) to use the capital and lower case of an alphabetical symbol to remember this concept of dominance and recessiveness. (Do not use T for tall and d for dwarf because you will find it difficult to remember whether T and d are alleles of the same gene/character or not). Alleles can be similar as in the case of homozygotes TT and tt or can be dissimilar as in the case of the heterozygote Tt. Since
NTA tests whether students understand dominance: the ability of one allele to mask another in heterozygotes. A dominant allele (like T) produces the same phenotype in both homozygotes (TT) and heterozygotes (Tt), while the recessive allele (t) only shows its effect in homozygous recessive organisms (tt). Students commonly confuse dominant with recessive alleles or incorrectly assume capital letters always represent dominant traits. Remember: dominance is about phenotypic expression in heterozygotes, not gene frequency. Always use the same letter (capital vs. lowercase) for alleles of the same gene—this prevents mixing up which traits pair together. This concept is fundamental to predicting inheritance patterns in Punnett squares.
Match the terms in Column I with their descriptions in Column II and choose the correct option. (NEET 2016 Phase 1) Column I A. Dominance B. Codominance C. Pleiotropy D. Polygenic Column II (i) Many genes govern a single character (ii) In a heterozygous organism only one allele expresses itself (iii) In a heterozygous organism both alleles express themselves fully (iv) A single gene inheritance influences many characters
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