Select the incorrect statement:

The correct answer is Option (2) → Chromosome 21 has the most genes and chromosome Y has the fewest.

These are features of the human genome found by the Human Genome Project.

Option (1) Chromosome 1 has the most genes and chromosome Y has the fewest. — A correct statement. Chromosome 1 has 2968 genes, the most, and the Y chromosome has 231, the fewest.

Option (2) Chromosome 21 has the most genes and chromosome Y has the fewest. — An incorrect statement. The record belongs to chromosome 1, not chromosome 21. Chromosome 21 is one of the smallest human chromosomes. An extra copy of it causes Down’s syndrome.

Option (3) Less than 2 percent of the genome codes for proteins. — A correct statement. Most of the genome does not code for proteins. Repeated sequences make up a very large part of it.

Option (4) The functions of over 50 percent of discovered genes are unknown. — A correct statement. The genes were found by sequencing, but what more than half of them do is still not known.

NCERT Extract:
Salient Features of Human Genome – “… (iv) The functions are unknown for over 50 per cent of the discovered genes.
(v) Less than 2 per cent of the genome codes for proteins.
(vi) Repeated sequences make up very large portion of the human genome.
(vii) Repetitive sequences are stretches of DNA sequences that are repeated many times, sometimes hundred to thousand times. They are thought to have no direct coding functions, but they shed light on chromosome structure, dynamics and evolution.
(viii) Chromosome 1 has most genes (2968), and the Y has the fewest (231).”