Do bacteria undergo mitosis?

No, bacteria do not undergo mitosis. Because they lack a nucleus, they divide using a simpler process called binary fission. Mitosis is strictly for eukaryotic cells (cells with a nucleus).

What happens if chromosomes don't separate correctly during meiosis?

If chromosomes fail to separate properly (a mistake called nondisjunction), the resulting egg or sperm cells can have an extra chromosome or be missing one. In humans, this can lead to conditions like Down syndrome.

Are the phases (Prophase, Metaphase, etc.) the same in both?

The names and basic mechanics are very similar. Mitosis uses PMAT (Prophase, Metaphase, Anaphase, Telophase) once. Meiosis goes through PMAT twice, known as Meiosis I and Meiosis II.

What is the difference between mitosis and meiosis?

The main difference between mitosis and meiosis is their purpose in your body. Mitosis is how we grow and heal, creating two exact cellular copies. Meiosis is how we reproduce, creating four genetically unique sperm or egg cells.<br><br>Think of mitosis like a photocopier making identical prints of a document. Meiosis, on the other hand, is like shuffling two decks of cards together and dealing out hands that have completely new combinations. Both are forms of cell division, but they follow different rules and end with very different results.

Purpose and Location

Mitosis happens in your somatic cells, which are the regular cells making up your skin, muscles, and organs. Its job is simple: replace dying cells and help you grow. Meiosis only happens in your germ cells, located in the testes or ovaries. Its sole purpose is to produce gametes (sperm and egg cells) for sexual reproduction.

Chromosome Counts: Diploid vs. Haploid

A normal human cell has 46 chromosomes, which is two sets of 23. We call this the diploid number, written in biology as $2n$ . Mitosis starts with a $2n$ cell and ends with two $2n$ cells. Meiosis cuts the chromosome number in half. It starts with a $2n$ cell but goes through two rounds of division to produce four cells, each with just one set of 23 chromosomes. These are called haploid cells, written as $n$ .

Creating Genetic Variation

Mitosis is designed to prevent variation. You want your new skin cells to act exactly like your old skin cells. Meiosis is designed to create variation. During the first phase of meiosis, chromosomes pair up and trade pieces of DNA in a process called 'crossing over.' Because of this, every sperm or egg cell produced is entirely unique, which is why you look different from your siblings.

Where Students Slip Up

A common mistake is confusing the two rounds of division in meiosis. Mitosis has one division step (one cell becomes two). Meiosis has two division steps: Meiosis I and Meiosis II (one cell becomes two, then those two become four). Students often forget that DNA is only copied once, right before both processes begin. It is never copied again between Meiosis I and Meiosis II.

Worked through

A fruit fly has a diploid chromosome number of $2n = 8$ . If a fruit fly cell undergoes mitosis, how many cells are produced and how many chromosomes does each contain? What if the cell undergoes meiosis?

First, let's look at mitosis. The goal is to make identical copies. One cell divides into two cells. Because the original cell was $2n = 8$ , both of the new cells will also have 8 chromosomes. They are identical diploid cells.<br><br>Next, let's look at meiosis. The goal is to make gametes for reproduction. The cell undergoes two rounds of division, so one cell divides into four cells. The chromosome number is cut in half from diploid ( $2n$ ) to haploid ( $n$ ). Therefore, each of the four resulting cells will have $n = 4$ chromosomes.

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Where this comes from: OpenStax Biology 2e: Chapter 10 (Cell Reproduction) and Chapter 11 (Meiosis and Sexual Reproduction) · Khan Academy: Cell division unit · Campbell Biology: Chapter 12 (The Cell Cycle) and Chapter 13 (Meiosis and Sexual Life Cycles)