For a species with a diploid number of 18, indicate how many chromosomes will be present in the somatic nuclei of individuals that are haploid, tetraploid, trisomic, and monosomic.

Key Concepts

Diploid and Haploid

Diploid (2n) refers to cells that contain two complete sets of chromosomes, one from each parent. In this case, a diploid number of 18 means there are 18 chromosomes in somatic cells. Haploid (n) cells, on the other hand, contain only one set of chromosomes, which would be half the diploid number, resulting in 9 chromosomes for this species.

Polyploidy

Polyploidy is a condition where a cell has more than two complete sets of chromosomes. Tetraploidy (4n) means there are four sets of chromosomes, which would result in 36 chromosomes for this species. Understanding polyploidy is essential for determining the chromosome number in organisms that have more than the typical diploid set.

Aneuploidy

Aneuploidy refers to the presence of an abnormal number of chromosomes in a cell, which can occur through the gain or loss of individual chromosomes. Trisomy indicates one extra chromosome (2n + 1), resulting in 19 chromosomes, while monosomy indicates one missing chromosome (2n - 1), leading to 17 chromosomes. Recognizing these variations is crucial for understanding genetic diversity and disorders.