Which of the following similarities is correct for both meiosis and mitosis

As you may already know, cells need to divide in order to replace old and damaged cells. However, did you know that there are different types of cell division? Mitosis and meiosis are both processes of cell division.

Mitosis produces identical daughter cells (with the same number of chromosomes) for growth or asexual reproduction. Meiosis, on the other hand, produces gametes for sexual reproduction by making genetically different daughter cells (with half the number of chromosomes). So, let's do a comparison of mitosis and meiosis!

• First, we will compare mitosis and meiosis on the basis of purpose.
• Then, we will look at the different stages of mitosis and meiosis.
• Lastly we will make a table to compare mitosis and meiosis.

Mitosis and Meiosis: Comparison of Purpose

To understand the differences between these two similar-sounding processes of cell division, which is the production of two or more daughter cells from a parent cell, it is important to note the purpose of mitosis and meiosis.

Mitosis and meiosis are both part of the cell division cycle in which the genetic material is divided in a process known as nuclear division.

Cytokinesis is the division of the cytoplasm, which follows the copying (interphase) and splitting of the genetic material (mitosis or meiosis), so that each new daughter cell has the appropriate number of chromosomes.

The purpose of mitosis

Nuclear division may be the shared purpose of mitosis and meiosis, but each has its separate purposes as well. Mitosis has multiple uses in organisms including:

• Making more cells for growth,

• Replacing old, worn out, or damaged cells,

• Asexual reproduction, where organisms produce genetically identical offspring.

Some animals, plants, fungi, and most single-celled organisms can use mitosis for asexual reproduction. If you followed our article on "Heredity" you might remember that asexual reproduction via mitosis produces clones, meaning organisms have the same genetic makeup as their parents. Reproduction via mitosis provides less genetic diversification.

Although not something humans can do, regeneration of limbs is something that scientists have been studying for some time in the animal kingdom. Animals such as the axolotl, an aquatic salamander native to Mexico, can produce new limbs after loss.

Regrowth through mitosis is especially important. After division, cells de-differentiate or lose their specific cell identity (i.e. skin cells) to become stem cells, which are cells that can become many types of cells with specific functions.

Scientists study frogs, starfish, axolotls, and more to understand how this growth and de-differentiation process works for potential medical science applications.

The purpose of meiosis

The purpose of meiosis is to produce gametes (sex cells) in sexually reproducing organisms. Females have egg cells, and males have sperm.

• Egg cells are produced in the ovaries, whereas sperm cells develop in the testes.

The product of meiosis is four haploid daughter cells. These haploid cells are genetically different from the parent cell and contain half the normal chromosome number (n) of typical cells.

When sexual reproduction occurs, the two haploid (n) cells come together to form a zygote, which is diploid and has two sets of chromosomes.

Gametes are mature haploid cells that are able to unite with a haploid cell of the opposite sex in order to form a zygote.

The Stages of Mitosis and Meiosis

The stages of mitosis and meiosis have the same names: prophase, metaphase, anaphase, and telophase, which are all followed by cytokinesis.

In meiosis, two rounds of division take place, so meiosis is split into meiosis I and meiosis II. The names of each stage within meiosis I or II also have an "I or II" placed at the end of their names (i.e., prophase I or prophase II).

Figure 1. Steps of mitosis and meiosis. Source: LadyofHats via commons.wikimedia.org

Interphase

Before the start of mitosis and meiosis, DNA duplication occurs during interphase to prepare for nuclear division.

Note: DNA duplication DOES NOT occur in between meiosis I and meiosis II, only before meiosis I.

Prophase

During prophase, in mitosis and meiosis (I & II), the following occur:

1. The nuclear envelope dissolves.

2. The centrosomes begin to migrate towards opposite poles.

3. The production of spindle fibers starts.

4. The chromosomes condense.

In meiosis I of meiosis, however, the homologous chromosomes form a tetrad, consisting of four chromatids, in which the non-identical chromosomes swap genetic material in a process known as crossing over. This does not happen during meiosis II or mitosis.

Metaphase

During metaphase in mitosis and meiosis, chromosomes line up at the metaphase plate. One difference is that, in meiosis I, chromosomes actually line up side-by-side to prepare for the homologous chromosomes to be separated. In mitosis and meiosis II, however, chromosomes line up single file at the plate.

Anaphase

During anaphase in mitosis and meiosis, chromosomes are pulled to opposite poles via the spindle fibers. They are attached at a point on the chromatids known as the kinetochore. During mitosis and meiosis II, sister chromatids are separated. Meiosis II still produces haploid cells, however, because homologous chromosomes are separated during anaphase I of meiosis I.

Telophase

During telophase, the nuclear envelope starts to reform, and chromosomes decondense. A cleavage furrow, the indentation of the cell membrane, begins to form. At the conclusion of telophase in mitosis, the two daughter cells will be diploid and genetically identical to the parent cell. At the end of telophase II in meiosis, there will be four haploid daughter cells.

These similarities take into the cell division in animal cells, which have centrosomes and a cleavage furrow. In plant cells, the spindle is said to originate from a microtubule-organizing center, and a cell plate forms instead of a cleavage furrow.

Summary of Mitosis and Meiosis Comparison

So far, we have gone over some important facts about the similarities and differences between mitosis and meiosis. Below, a figure highlights the nuclear (chromosomal) differences at the end of meiosis and mitosis (Fig. 2) and the table summarizes what we have discussed (Table 1).

What is common in both meiosis and mitosis?

What are the similarities and difference between mitosis and meiosis?

Which is a correct comparison of meiosis and mitosis?