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#dominant traits

4 public questions tagged with this topic.

BOTANY

Which of the following statements about dominant and recessive traits is incorrect?

Dominant traits are not necessarily more common; frequency depends on factors like natural selection and genetic drift. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Botany section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Botany portion (Latest NCERT Textbooks for Academic Session 2026-27 -

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Pedigree Analysis

X-linked dominant traits

X-linked dominant allele located on X chromosome expresses phenotype even in heterozygous female. Affected father X^A Y transmits X^A containing dominant allele to all daughters via X-bearing sperm, making every daughter affected regardless of maternal genotype, while sons receive paternal Y and are unaffected unless mother also carries trait. This father-to-all-daughters transmission pattern is hallmark of X-linked dominant pedigrees, distinguishing it from autosomal dominant where father passes trait to half offspring irrespective of sex. Affected mothers pass trait to half sons and half daughters.

Ref: NCBI Bookshelf, Hartl, X-linked Dominant Inheritance Patterns and Pedigree Features

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Genetic Crosses

In a trihybrid cross, the probability of showing at least one dominant trait is

Trihybrid cross AaBbCc x AaBbCc with independent assortment and complete dominance at each locus involves three independent segregation events. Probability offspring receives no dominant allele, i.e., homozygous recessive aabbcc, equals product of individual recessive probabilities (1/4)*(1/4)*(1/4)=1/64. Complementary event showing at least one dominant trait therefore equals 1 minus all recessive probability, 1-1/64=63/64. Calculation employs product rule for independent events and complement rule for union. Includes classes expressing one, two, or three dominant phenotypes, useful for predicting proportions in multigenic traits.

Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 2: Probability Rules for Trihybrid Cross

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