Q.48 Which one of the following statements having the terms – gene, chromosome and genome is
CORRECT?
(A) The rice gene contains about 50,000 genomes located on 12 different chromosomes
(B) The rice genome contains about 50,000 genes located on 12 different chromosomes
(C) The rice chromosome contains about 50,000 genes located on 12 different genomes
(D) The rice genome contains about 50,000 chromosomes located on 12 different genes

 Introduction

In genetics and genomics, the terms gene, chromosome, and genome are closely related but often confused in exams. Competitive examinations like CSIR-NET, GATE, DBT, JAM, and UPSC frequently test conceptual clarity using such terminology-based questions.

This article explains the correct relationship between gene, chromosome, and genome, using rice (Oryza sativa) as a reference organism, and evaluates all given options in detail.

---

 Basic Definitions (Very Important for Exams)

🔹 Gene

• A gene is a functional unit of heredity

• It is a segment of DNA that codes for a protein or functional RNA

🔹 Chromosome

• A chromosome is a long DNA molecule containing many genes

• Rice has 12 chromosomes (haploid set)

🔹 Genome

• A genome is the entire genetic material of an organism

• It includes all genes distributed across all chromosomes

---

 The Rice Genome – Key Facts

• Organism: Rice (Oryza sativa)

• Haploid chromosome number: 12

• Total number of genes: ~50,000 (approximate value used in exams)

• All genes together form one genome

---

Correct Answer

Option (B): The rice genome contains about 50,000 genes located on 12 different chromosomes

✔ This statement correctly uses all three terms:

• Genome → complete genetic content

• Genes → ~50,000 functional units

• Chromosomes → distributed across 12 chromosomes

---

 Explanation of All Options

Option (A): The rice gene contains about 50,000 genomes located on 12 different chromosomes

• A gene cannot contain genomes

• Genome is much larger than a gene
  Conceptually incorrect

---

Option (B): The rice genome contains about 50,000 genes located on 12 different chromosomes ✅

• Genome = total genetic material

• Genes = functional units

• Chromosomes = structural units carrying genes
  ✔ Scientifically and conceptually correct

---

Option (C): The rice chromosome contains about 50,000 genes located on 12 different genomes

• Rice has 12 chromosomes, not 12 genomes

• A single chromosome does not contain all genes
  Incorrect hierarchy

---

Option (D): The rice genome contains about 50,000 chromosomes located on 12 different genes

• Completely reverses definitions

• Genes do not contain chromosomes
  Incorrect

---

 Exam-Oriented Takeaways

• Genome = all genes + all chromosomes

• Genes are parts of chromosomes

• Chromosomes collectively form the genome

• Rice has:

  • ~50,000 genes

  • 12 chromosomes

  • 1 genome

Memory Trick:

Genes live on chromosomes, and all chromosomes together make the genome.