Ploidy (Pre-IB SC 9)
What is diploid?
When a cell contains two sets of chromosomes, it is diploid.
What is haploid?
When a cell contains one type of chromosome it is haploid.
Examples of diploid cells:
Muscle cells, liver cells, skin cells, bone cells, nerve cells, etc.
Examples of haploid cells:
Sperm cells, egg cells
What does symbol n represent?
One set of chromosome, so n is haploid number
What does symbol 2n represent?
Diploid number
What is "n"?
Number of chromosome types
Haploid cells in relation to diploid?
Haploid cells have half of the chromosomal set of a diploid cell.
(Diploid in humans = 46, so haploid in humans = 23.)
In which phase are the chromosomes duplicated? Does the ploidy change or stay the same? (Human cells)
- S phase, interphase
- Still 46 chromosomes, because the sister chromatids are connected with a centromere, and chromosomes are counted by their centromeres
- 92 chromatids
At the end of mitosis, how does the ploidy number stay the same/change?
- The 92 chromatids seperate, ending up with two cells with 46 chromosomes and 46 chromatids.
In meiosis, (human cells), how does the ploidy change/stay the same?
- Meiosis is a REDUCTION DIVISION
- The number of chromosomes per cell is cut in half due to the seperation of homologous chromosomes.
- The 4 daughter cells produced have half the amount of chromosomes are the original cell.
- They are haploid
- Original cell: 46 chromosomes, 46 chromatids
- Ending cells: 23 chromosomes, 23 chromatids