A diploid plant carries two full sets of chromosomes in its body cells, one set from the pollen parent and one from the seed parent. Normal cannabis is diploid with 2n = 20 chromosomes. Its pollen and ovules are haploid (n = 10), so fertilisation restores the diploid number.
In practice
Diploidy is why every gene comes in two copies and why simple Mendelian ratios work. With two alleles per locus a plant is either homozygous or heterozygous, and a heterozygote passes each allele to half its gametes.
Almost all cannabis grown today is diploid. Polyploid plants (triploids with three sets, tetraploids with four) are made deliberately, for example to produce mostly seedless triploid crops, and they do not follow diploid ratios.
Cannabis: haploid n = 10; diploid 2n = 20; triploid 3n = 30; tetraploid 4n = 40.
Don't confuse with
- Polyploid: more than two chromosome sets.
- Haploid: one set, as in pollen and egg cells.
- Dioecious: separate male and female plants. Cannabis is both diploid and dioecious, but the two words describe different things.
A chromosome is one long DNA molecule packaged with proteins that carries many genes; cannabis normally has 10 pairs, nine autosome pairs plus an X/Y sex pair.Mendelian inheritance is the pattern in which single genes pass from parents to offspring in predictable ratios, following Mendel's laws of segregation and independent assortment.An allele is one version of a gene; a diploid cannabis plant carries two alleles at each locus, one from each parent, which may be the same or different.A locus is the fixed position on a chromosome where a particular gene or DNA marker sits; the plural is loci.A plant is homozygous at a locus when it carries two identical alleles there (AA or aa), so it passes the same allele to every offspring.A plant is heterozygous at a locus when it carries two different alleles there (Aa), so its offspring can inherit either one and segregate.A polyploid plant carries more than two full sets of chromosomes, such as a triploid (three) or tetraploid (four); in cannabis these are almost always bred deliberately.Having male and female flowers on separate individual plants; drug-type cannabis is naturally dioecious with an XY sex-chromosome system.
