A chromosome is a single long DNA molecule, wrapped around proteins, carrying hundreds to thousands of genes in a fixed order. Cannabis is diploid with 2n = 20: nine pairs of autosomes plus one pair of sex chromosomes, XX in females and XY in males (Divashuk et al. 2014).
In practice
Chromosomes are why genes travel in groups. During meiosis each pair separates, so every pollen grain and ovule receives one copy of each of the ten chromosomes, with some segments swapped between the pair by crossing over. Genes on different chromosomes assort independently; genes close together on one chromosome are linked.
Growers meet chromosomes most directly through sex. A female (XX) reversed to make pollen still only carries X chromosomes, so its pollen gives all-female (XX) seed. That is the basis of feminised seed.
Some cultivated plants have extra whole sets of chromosomes (polyploids). Triploid and tetraploid cannabis exist, mostly from deliberate breeding.
Don't confuse with
- Genome: the full DNA content of a cell across all chromosomes.
- Gene: a small part of one chromosome.
- Chromatid: one of the two copies of a chromosome after it has duplicated before cell division.
