In general, the domesticated potatoes are compatible for breeding when they have the same level of ploidy. Cross a diploid with a diploid and you get a diploid; cross a tetraploid with a tetraploid and you get a tetraploid….Endosperm Balance Number.

48 chromosomes

11 chromosomes

18 chromosomes

46

Typically, a baby is born with 46 chromosomes. Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is ‘trisomy. ‘ Down syndrome is also referred to as Trisomy 21.

“This is because in the human evolutionary lineage, two ancestral ape chromosomes fused at their telomeres [tips], producing human chromosome 2. Thus, humans have one fewer pair of chromosomes. It means each parent contributes one homologue to a homologous pair of chromosomes in their child’s cells.

chimpanzees

autosomes

A change in the number of chromosomes can cause problems with growth, development, and function of the body’s systems. These changes can occur during the formation of reproductive cells (eggs and sperm), in early fetal development, or in any cell after birth.

The X and Y chromosomes are not autosomes. However, chromosome 21 is actually shorter than chromosome 22. This was discovered after the naming of Down syndrome as trisomy 21, reflecting how this disease results from possessing one extra chromosome 21 (three total).