The M&Ms of Genetics

By A.K. Matai

Mitosis Overview

Mitosis is the process by which a eukaryotic cell nucleus splits into two followed by the division of a parent cell into two daughter cells. During prophase, the replicated chromosome is condensed into a structure consisting of two sister chromatids held together by the centromere. Two DNA binding proteins – condensin and cohesin – help condense the chromosomes. Condensin condenses the chromosomes into a highly compact form while cohesin holds the sister chromatids together. In metaphase, chromosomes align along the metaphase plate. During anaphase, cohesin breaks down and the sister chromatids are pulled apart to opposite ends of the cell. Telophase and cytokinesis mark the end of mitosis as the nucleus is reformed and the cells is physically split into two daughter cells.

Meiosis Overview

 Meiosis, on the other hand, is a type of cell division that is required to produce gametes. Meiosis I is responsible for producing haploid cells as homologous pairs of chromosomes on the equatorial plate are pulled apart in anaphase I. Meiosis II is a mitotic division of the haploid cells produced in meiosis I as the sister chromatids are pulled apart to produce four haploid daughter cells that go on to become a sperm or an egg.

What is n? What is c?

 n is the number of chromosomes present in a haploid cell while c is the amount of DNA present in a haploid cell. Here is a graph outlining the changes in n and c value throughout mitosis and meiosis.

The M&Ms of Genetics 2.jpg

The Moment of Truth

Now is the time to visually combine the concepts of mitosis, meiosis, n value and c value. Here is a diploid organism that has 2N=6 going through mitosis and meiosis with the n and c values clearly labeled.

The M&Ms of Genetics 1

Questions, Comments or Concerns?

Feel free to post a your questions, comments or concerns down below!

References

Locke, John; Deyholos, Michael; Harrington, Michael; Canham, Lindsay; Kang, Min, “Open Genetics Lectures (OGL) Fall 2016”

Evan Amos. M&Ms. 2011. https://commons.wikimedia.org/wiki/File:Plain-M%26Ms-Pile.jpg. Web. 19 Mar. 2017.

 

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