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NCERT Exemplar · Q11

Q.The human chromosome with the highest and least number of genes in them are respectively:

(a) Chromosome 21 and Y
(b) Chromosome 1 and X
(c) Chromosome 1 and Y
(d) Chromosome X and Y
Mahe DhseMCQ· 1mImportance★★★★★est
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Chromosome 1, the largest human chromosome, carries the most genes (~2968), while the Y chromosome, the smallest, carries the fewest (~231). The answer is (C) Chromosome 1 and Y.

When the Human Genome Project completed its monumental task of sequencing all human DNA in 2003, one of the striking revelations was how unevenly genes are distributed across our 23 pairs of chromosomes. Size matters here, but not in a perfectly linear way—the correlation between chromosome length and gene count is strong but not absolute.

Chromosome 1 stands as the giant of the human genome. It is the longest chromosome, spanning roughly 249 million base pairs, and houses approximately 2968 genes. This makes it the most gene-dense in absolute terms, encoding proteins involved in everything from cell division to immune response. Think of it as the encyclopedia volume with the most entries—sheer physical size translates to more genetic real estate.

At the opposite extreme sits the Y chromosome, the defining feature of biological maleness. Tiny in comparison—only about 59 million base pairs—it carries a mere 231 genes. Many of these are involved in male sex determination and spermatogenesis, but the Y chromosome has lost most of its genetic material over evolutionary time. It's a stripped-down specialist, carrying just enough information for its specific role. …

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