Cytologists had been studying chromosome behavior since the late 19th century. Why did it take until 1956 to figure out the correct human chromosome number, thanks to Joe Hin Tjio and Albert Levan?

explains that humans have 23 pairs of chromosomes: 22 autosomes and one pair of sex chromosomes—XX in females and XY in males ...

In humans, diploid cells contain 46 chromosomes, with 23 chromosomes inherited from the ... During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and ...

Females have one active X chromosome and one dormant X chromosome in each cell. But a study suggests that genes on the dormant X get "reawakened" later in life, potentially giving the brain a boost.