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5.1 Meiosis






⏱️  2 min read

written by

Caroline Koffke

caroline koffke

May 30, 2020

Meiosis is the process that all organisms go through in order to produce gametes, or sex cells. The process differs from mitosis, the process of somatic cell division, in a number of key ways. Meiosis involves one round of DNA replication and two rounds of cellular division. The resulting cells are all genetically unique from one another and from the parent cell. The resulting cells are also haploid, meaning that they have half of the genetic content of a typical somatic cell, or diploid cell.


Image courtesy of WikiMedia Commons.

The diagram below will walk through the steps that take place in meiosis and their importance to the creation of egg and sperm.

1️⃣ Step 1

Step 1 shows the replication of DNA, as the cells now have the signature “X” formation of a duplicated chromosome. 

2️⃣ Step 2

Step 2 shows homologous chromosomes pairing up. Homologous chromosomes are different versions of the same chromosome. For example, humans have two versions of 23 chromosomes, for a total of 46 chromosomes. During this step of meiosis, our two different versions of our 23 chromosomes would pair up with one another in preparation for division.

3️⃣ Step 3

Step 3 shows the action of crossing over between homologous chromosomes, a process that will be thoroughly discussed in the next section.


Image courtesy of WikiMedia Commons

4️⃣ Step 4

Step 4 shows the first round of cellular division, resulting in the splitting of homologous chromosomes. The chromosomes that remain are referred to as sister chromatids.

5️⃣ Step 5

Step 5 shows the second round of cellular division, resulting in four genetically unique daughter cells. In comparison to the starting cell on the left hand side, the daughter cells have half the amount of chromosomes.

The AP exam does NOT require you to know the specific phases of cellular division (Prophase, Metaphase, Anaphase, and Telophase), so focus your energy on remembering how the chromosomes generally move and how the process contributes to genetic diversity.

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