Genetics Workshop Number One
Cytokinesis is cell division. It is NOT nuclear division.
What are the names for the two types of nuclear division?
Mitosis & meiosis
Define mitosis. What does it make?
Mitosis is "copy division" so it produces identical
Mitosis increases the number of nuclei.
What is achieved in mitosis in terms of the genetic materials?
Mitosis distributes exact copies of genetic material so the daughter nuclei are genetically identical to each other and identical to the mother nucleus from which they came. The main function of mitosis is to increase the number of nuclei.
What word is used to describe a single set of chromosomes (n)?
What word is used to describe two sets of chromosomes (2n)?
In the spaces below draw the important structures that identify each phase paying particular attention where needed to chromosomes, centrosomes and both cell and nuclear membranes. Assume it is an animal cell starting with four chromsomes.
1. Interphase (late)
2. Prophase (late) or Prometaphase
Has 8 chromosomes
Still has 8 chromosomes (but you cannot see them) equally distributed between the two nuclei.
6. Cytokinesis (after mitosis)
showing early interphase
Each cell has 4 chromosomes
Meiosis is often called "reduction division" because the genetic material is reduced by half - from diploid to haploid.
What is achieved in meiosis in terms of the genetic materials? Why is meiosis necessary? Where does meiosis occur?
Meiosis produces diverse HAPOLID (n) nuclei.
If cells did not undergo meiosis, the fusion of (diploid) gametes would produce zygotes with twice as much genetic material as needed. This overload of genes is often lethal, so meiosis is required to produce healthy gametes and, thus, healthy zygotes.
Meiosis is a very specialized type of nuclear division occurring only in cells that will become gametes (sex cells - sperm and egg). So meiosis is required for sexual reproduction using gametes.
In the spaces below draw the important structures that identify each phase paying particular attention where needed to chromosomes, centrosomes and both cell and nuclear membranes. Show a cell that has a diploid number of 4 (2n = 4) and color or otherwise mark the M and P chromosomes and be sure you show proper tetrad/dyad patterns throughout. Assume it is an animal cell.
1. Metaphase I||
2. Anaphase I
3. Metaphase II
Summary of meiosis showing the ploidy and of the cell as it goes through meiosis I and meiosis II with the cytokinesis required to turn one diploid cell into four haploid cells. Assume a cell that has a diploid number of 4 (2n = 4)
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