Chromosome 1 spans about 249 million nucleotide base pairs, which are the basic units of information for DNA.

[5] It was the last completed chromosome, sequenced two decades after the beginning of the Human Genome Project.

Patterns of sequence variation reveal signals of recent selection in specific genes that may contribute to human fitness, and also in regions where no function is evident.

Complete monosomy (only having one copy of the entire chromosome) is invariably lethal before birth.

[13] Complete trisomy (having three copies of the entire chromosome) is lethal within days after conception.