Which chromosome is the largest of the 23 human chromosome pairs?

Chromosome 1 is the largest human chromosome.

It is the first chromosome in the standard human karyotype and contains about 249 million DNA base pairs. That is roughly 8% of the DNA in a human haploid genome, although exact estimates vary with the reference assembly and what regions are counted.

Chromosome 1 carries hundreds of protein-coding genes, including genes involved in cell growth, development and metabolism. Changes affecting this chromosome have been linked with a wide range of inherited conditions and cancers. Its size does not mean that every gene on it is more important than genes on smaller chromosomes.

Chromosome 21 is a common mix-up because it is associated with Down syndrome, but it is one of the smallest human chromosomes. Chromosome 22 is also an autosome and is larger than chromosome 21, while the X chromosome has a different role in sex determination and dosage compensation.