Ploidy Number

[Tokophyra125]

For some reason "calculating" the diploid and haploid number of an organism/cell is messing me up. If I have a cell with four pairs of homologous chromosomes, the diploid number should be four, right? Also, if there is an organism with a haploid number of X then what would the number for a bivalent, sister chromatid, and a nucleus after DNA replication be?

[Tokophyra125]

Sorry, rather a diploid number of 4.

[biogeek02]

Check out http://www.bioinmotion.com for cool vids about meiosis and mitosis!

[Cat]

For some reason "calculating" the diploid and haploid number of an organism/cell is messing me up. If I have a cell with four pairs of homologous chromosomes, the diploid number should be four, right? Also, if there is an organism with a haploid number of X then what would the number for a bivalent, sister chromatid, and a nucleus after DNA replication be?

The whole thing is wrong.

Vocabulary:

Haploid – half of total number of chromosomes
Mono– one
Di – Two
Tetra – four
Octa – eight

Cell that has only 1 set of chromosomes (no sister chromatids) is monoploid. Monoploid is sometimes treated as synonym of haploid when haploid number happens to be 1.

Cell that has 2 of each chromosome (like humans) are diploid.

Cells from your example, that have four pairs of homologous chromosomes in reality have 8 copies of each chromosome and, therefore, octaploid.

Haploid cell will have half of chromosomes in original somatic cell. So if original is diploid (2n), haploid is 1n; if original is octaploid (8 of each chromosome), haploid has 4 sets of each chromosome.