Human Chromosomes Labeled – Karyotype and One Pair

All 9 parts on the diagram

Show the list

The karyotype 4

Autosomes The 22 numbered pairs. They are numbered roughly by size, so pair 1 is the largest.
Sex chromosomes The 23rd pair, named by letter. Females have two X chromosomes; males have one X and one Y.
X chromosome The larger sex chromosome. Females have two of them and males have one.
Y chromosome The small sex chromosome. Males have one X and one Y.

One pair, before and after copying 5

Homologous chromosomes A matching pair, one from each parent. They are the same size and carry the same genes in the same places.
Alleles Two versions of the same gene. One sits on each chromosome of the pair, at the same place.
DNA replication (copying) The cell copies its DNA before it divides. After this step each chromosome is two joined copies.
Sister chromatids The two identical copies of one chromosome. They stay joined until the cell divides.
Centromere The pinched region of a chromosome. Sister chromatids stay joined here, and spindle fibers attach to it.

How this list was compiled: Every name and count checked on 2026-10-03 against the Talking Glossary of the National Human Genome Research Institute (Karyotype, Autosome, Sex Chromosome, X Chromosome, Y Chromosome, Chromosome, Chromatid, Centromere, Allele, Crossing Over; https://www.genome.gov/genetics-glossary), MedlinePlus Genetics of the National Library of Medicine (How many chromosomes do people have? and What is a chromosome?; https://medlineplus.gov/genetics/understanding/basics/howmanychromosomes/) and Wikipedia, text only: Karyotype, Homologous chromosome, Sister chromatids, Chromosome 1, Chromosome 21. Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. A schematic, not a photograph. Licence: own work

How it works

Human chromosomes labeled on two drawings: a karyotype, the whole set lined up in pairs, and a homologous chromosomes diagram labeled before and after the DNA is copied. Read the names first, then press Quiz me.

Read the full guide

Read the karyotype

A human cell normally holds 46 chromosomes in 23 pairs. Pairs 1 to 22 are the autosomes, numbered roughly from the largest to the smallest. The last pair is the sex chromosomes: two X chromosomes in females, one X and one Y in males.

Read one pair

The two chromosomes of a numbered pair are homologous: one came from each parent, and they carry the same genes, sometimes as different alleles. Before a cell divides it copies its DNA, and each chromosome becomes two sister chromatids joined at the centromere.

Homologous chromosomes are two separate chromosomes. Sister chromatids are two copies of one.

Questions and answers

How many chromosomes do humans have?

46 in most cells, in 23 pairs: 22 pairs of autosomes and one pair of sex chromosomes. One chromosome of each pair comes from each parent.

What is a karyotype?

A person's complete set of chromosomes, and also the picture of them lined up in pairs in number order. The drawing here is a schematic of a typical set in plain shapes, not a photograph.

What is the difference between homologous chromosomes and sister chromatids?

Homologous chromosomes are a pair, one from each parent, with the same genes but not always the same alleles. Sister chromatids are the two identical copies of one chromosome, made when the DNA is copied and joined at the centromere.

Which human chromosome is the largest?

Chromosome 1. The autosomes are numbered roughly by size, from the largest pair down. The smallest is chromosome 21, a little smaller than chromosome 22.

Can I practice here for “drag the labels to the correct locations on these images of human chromosomes.”?

Yes, for practice. That sentence is the instruction of a labeling exercise. The drawings here are our own and not a copy of any course figure, so your figure may show other views or ask for other names.