Definitions

See - Burnham, C.R. 1984. Discussions In Cytogenetics. Burges Publ. Co.

The basic set of chromosomes is called a genome. One set of chromosomes (X) is normally contained in the gametes of diploid organisms, and somatic cells contain two sets(2X). Polyploid cells contain more than two genomes.

haploid - contains one of each homologous chromosome(X) in a gamete.

diploid - contains both homologous chromosomes for each set of non-homologous chromosomes (2X).

triploid - contains three of each set of non-homologous chromosomes (3X).

tetraploid - contains four of each set of non-homologous chromosomes (4X).

pentaploid - (5X)

hexaploid - (6X)

octaploid - (8X)

Euploid - organisms that contain a complete multiple of the basic set of chromosomes.

Aneuploid - organisms that do not contain an exact multiple of the basic set of chromosomes. (More or less than (a)x sets with "a" as a whole number).

Polysomy - an organism has extra copies of individual chromosomes.

trisomic - a diploid organism with an extra copy of one chromosome (2X+1)

tetrasomic - a diploid organism with two extra copies of an individual chromosome (2X+2).

monosomic - a diploid organism missing one copy of an individual chromosome (2X-1).

nullisomic - an organism missing both copies of an individual chromosome 2(X-1).

primary trisomic - a diploid organism with an extra copy of an individual whole chromosome (2x+1).

secondary trisomic - a diploid organism with an extra chromosome. The extra chromosome is a doubled half-chromosome. One arms of one chromosome was doubled.

Where the arms of the first chromosome are labeled 1 an 2.

tertiary trisomic - a diploid organism with an extra chromosome. The extra chromosome is the result of a reciprocal translocation.

Autoploidy - all the chromosomes in the polyploid organism are derived from a single diploid ancestor.

Monoploids - a zygote has a single genome. During meiosis the chromosomes have no homologues with which to pair, so they pass as univalents onto the metaphase plate where they segregate at random.

Autotriploid - three sets of genomes from the same origin. These types often arise through the fusion of a diploid gamete with a haploid gamete. During meiosis gametes have varying numbers of non-homologous chromosomes from X to 2X. The three homologous chromosomes that pair result in unequal chromosome distribution to the poles.

Autotetraploid - These individuals have four complete sets of chromosomes(4X) which is the result of a doubling of the diploid set from the same ancestor. Autotetraploids may result from failure of normal nuclear division or from the union of two diploid gametes. i.e. potato

Autohexaploid - These individuals have six genomes from the same source. i.e. sweet potato

Allopolyploid - Polyploid organisms that process two or more genomes derived from different species.

Amphiploid - an individual with a double set of different genomes. For example, triticale is a wheat x rye hybrid with a doubled set of both genomes.

Allotetraploid - an individual processing two genomes from one specie and two genomes from another specie. Durum wheat has AABB which is two copies of both the A and B genomes.

Allohexaploid - an individual with three complex sets of genomes, each set from a different ancestor. One genome from specie A, one genome from specie B, and a third genome derived from specie C for a total genomic content AABBCC as in bread wheat.