Which chromosome in the human genome has the highest number of genes? | NEET Biology PYQ Solution
Which chromosome in the human genome has the highest number of genes?
  • (A) Chromosome 1
  • (B) Chromosome 10
  • (C) Chromosome X
  • (D) Chromosome Y
Correct Answer: (A) Chromosome 1

Explanation & Analysis

In the Human Genome Project (HGP), scientists mapped the entire genetic sequence of humans. They found that genes are not distributed equally across all chromosomes. Some are "gene-rich" while others are "gene-poor."

Chromosome 1 is the largest autosome in the human body. Because of its massive size (approximately 249 million base pairs), it naturally carries the most genetic information. According to NCERT and HGP data, Chromosome 1 contains 2,968 genes. Conversely, the Y Chromosome is the smallest and contains the fewest genes, only 231.

Deep Dive: The Human Genome & Chromosomal Mapping

1. The "Mega Project": Human Genome Project (HGP)

Launched in 1990, the HGP was a 13-year international research effort. It aimed to identify all the approximately 20,000-25,000 genes in human DNA and determine the sequences of the 3 billion chemical base pairs. It was called a "Mega Project" due to its cost (3 Billion USD) and the vast amount of data generated.

2. Key Findings for NEET Preparation

  • Total Base Pairs: The human genome has 3164.7 million nucleotide bases.
  • Average Gene Size: An average gene consists of 3000 bases, but sizes vary. Dystrophin is the largest known gene (2.4 million bases).
  • Non-Coding DNA: Surprisingly, less than 2% of the genome codes for proteins. Most of it consists of repetitive sequences.
  • SNP (Single Nucleotide Polymorphisms): There are about 1.4 million locations where single-base DNA differences occur in humans.

3. Chromosome 1 vs Chromosome Y

Chromosome 1 was the last chromosome to be completely sequenced (May 2006). It holds the record for the highest gene count (2968). The Y-chromosome, being the smallest sex chromosome, carries the least number of genes (231), mainly those related to male fertility (SRY gene).

4. Genomic Distribution Table

FeatureChromosome 1Chromosome Y
Total Genes2968231
SizeLargest (~249 Mb)Smallest (~57 Mb)
Sequencing DateCompleted May 2006Completed earlier

5. Repetitive Sequences

A large portion of the human genome is made of repetitive sequences. These sequences are thought to have no direct coding function, but they shed light on chromosome structure, dynamics, and evolution. They are highly useful in DNA Fingerprinting.

6. Bioinformatics

The HGP led to the rapid development of a new area in biology called Bioinformatics. It involves using high-speed computational devices for data storage, retrieval, and analysis. Without bioinformatics, managing 3 billion base pairs would be impossible.

7. Ethical, Legal, and Social Issues (ELSI)

The HGP also funded the ELSI program to anticipate and address the implications of genomic research on individuals and society, such as genetic privacy and potential discrimination.

Frequently Asked Questions (FAQs)

1. Which is the largest human chromosome?
Chromosome 1 is the largest human chromosome.
2. Which chromosome has the lowest number of genes?
The Y chromosome has the fewest genes (231).
3. What is the total number of bases in the human genome?
Approximately 3.16 billion base pairs.
4. What percentage of the human genome codes for proteins?
Less than 2%.
5. What is the largest known human gene?
Dystrophin (2.4 million bases).
6. How many genes does Chromosome 1 have?
It has exactly 2,968 genes.
7. When was Chromosome 1 sequencing completed?
In May 2006.
8. What is an SNP?
Single Nucleotide Polymorphism – single base differences in DNA.
9. Who is the father of DNA sequencing?
Frederick Sanger developed the method used in HGP.
10. What is the significance of junk DNA?
It helps in understanding chromosome evolution and structure.

Related Covered Topics

Human Genome Project FeaturesChromosome 1 gene countNCERT Molecular Basis of InheritanceNEET Biology PYQLargest human gene DystrophinSmallest chromosome YSNP in human genomeBioinformatics applicationsDNA Sequencing techniquesTotal genes in human genomeNEET 2026 PreparationMedical Entrance Exams India

Authored by: NEET Biology Expert Team

Specialists in Molecular Genetics and Human Physiology for NEET-UG preparation.

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