Q.16 Mendel’s ‘law of segregation’ applies to the segregation of ________ during
gamete formation.
(A) mitochondrial genes
(B) alleles of a gene
(C) linked genes on the same chromosome
(D) unlinked genes on the same chromosome
This article dives into Mendel’s foundational law of segregation, a key concept in genetics, with a detailed breakdown of a common multiple-choice question. Perfect for students preparing for exams in biology, genetics, or biotechnology.
What is Mendel’s Law of Segregation?
Mendel’s law of segregation forms one of the pillars of classical genetics. It states that during gamete formation (meiosis), the two alleles for each gene separate from each other, so each gamete receives only one allele. This ensures genetic diversity in offspring.
Gregor Mendel discovered this through pea plant experiments in the 1860s, observing how traits like seed color segregated independently. The law applies specifically to alleles of a gene, making it fundamental to understanding inheritance patterns.
Correct Answer: (B) alleles of a gene
This option perfectly captures the essence of the law. Alleles are alternative forms of the same gene (e.g., tall vs. dwarf height in peas). During meiosis, homologous chromosomes separate, and each gamete gets one allele, preventing blending inheritance.
Detailed Explanation of All Options
Let’s break down why each option fits or fails, using clear genetics principles.
Option (A) Mitochondrial Genes
Mitochondrial genes reside in the mitochondria’s DNA (mtDNA), inherited maternally without segregation like nuclear genes. They don’t undergo meiotic division or pair with paternal alleles. Mendel’s law targets nuclear genes on chromosomes, so this is incorrect.
Option (B) Alleles of a Gene
Correct. For a diploid organism with alleles A (dominant) and a (recessive), meiosis produces gametes with either A or a in equal ratios (1:1). This segregation explains monohybrid crosses, like Mendel’s 3:1 phenotypic ratio in F2 generations.
Option (C) Linked Genes on the Same Chromosome
Linked genes are on the same chromosome and tend to inherit together, violating independent segregation unless crossing over occurs. Mendel’s law assumes alleles on homologous chromosomes segregate freely—it doesn’t apply directly to linked genes, which show linkage disequilibrium.
Option (D) Unlinked Genes on the Same Chromosome
Unlinked genes assort independently (Mendel’s second law), but if on the same chromosome, they are linked by definition unless far apart. The phrasing is tricky and incorrect for segregation; this relates more to dihybrid crosses, not the core law of segregation for a single gene’s alleles.
Why This Matters in Modern Genetics
Mendel’s law underpins Punnett squares, Hardy-Weinberg equilibrium, and even CRISPR gene editing, where we manipulate specific alleles. For exams, remember: segregation = alleles separating in meiosis.
Test your knowledge—try solving a monohybrid cross!
