How do mitosis and meiosis differ in the daughter cells that are produced

Cells divide and reproduce in two ways: mitosis and meiosis. Mitosis is a process of cell division that results in two genetically identical daughter cells developing from a single parent cell. Mitosis is used by single-celled organisms to reproduce; it is also used for the organic growth of tissues, fibers, and membranes.

Meiosis, on the other hand, is the division of a germ cell involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell. Meiosis plays a role in sexual reproduction of organisms. The male and female sex cells (i.e., egg and sperm) are the end result of meiosis; they combine to create new, genetically different offspring.

What is the role and purpose of mitosis and meiosis?

Though both types of cell division are found in many animals, plants, and fungi, mitosis is more common than meiosis and has a wider variety of functions. Not only is mitosis responsible for asexual reproduction in single-celled organisms, but it is also what enables cellular growth and repair in multicellular organisms, such as humans. In mitosis, a cell makes an exact clone of itself. This process is what is behind the growth of children into adults, the healing of cuts and bruises, and even the regrowth of skin, limbs, and appendages in animals like geckos and lizards.

Meiosis is a more specific type of cell division (of germ cells, in particular) that results in gametes, either eggs or sperm, that contain half of the chromosomes found in a parent cell. Unlike mitosis with its many functions, meiosis has a narrow but significant purpose: assisting sexual reproduction. It is the process that enables children to be related but still different from their two parents.

Meiosis and Genetic Diversity

Sexual reproduction uses the process of meiosis to increase genetic diversity. Offspring created through asexual reproduction (mitosis) are genetically identical to their parent, but the germ cells created during meiosis are different from their parent cells. Some mutations frequently occur during meiosis. Further, germ cells have only one set of chromosomes, so two germ cells are required to make a complete set of genetic material for the offspring. The offspring is therefore able to inherit genes from both parents and both sets of grandparents.

Genetic diversity makes a population more resilient and adaptable to the environment, which increases chances of survival and evolution for the long term.

Mitosis as a form of reproduction for single-cell organisms originated with life itself, around 3.8 billion years ago. Meiosis is thought to have appeared around 1.4 billion years ago.

Mitosis and Meiosis Stages

Cells spend about 90% of their existence in a stage known as interphase. Because cells function more efficiently and reliably when small, most cells carry out regular metabolic tasks, divide, or die, rather than simply grow larger in the interphase. Cells "prepare" for division by replicating DNA and duplicating protein-based centrioles. When cell division begins, the cells enter into either mitotic or meiotic phases.

In mitosis, the end product is two cells: the original parent cell and a new, genetically identical daughter cell. Meiosis is more complex and goes through additional phases to create four genetically different haploid cells which then have the potential to combine and form a new, genetically diverse diploid offspring.

Stages of Mitosis

What are the four stages of mitosis?

There are four mitotic phases: prophase, metaphase, anaphase, and telophase. Plant cells have an additional phase, preprophase, that occurs before prophase.

• During the mitotic prophase, the nuclear membrane (sometimes called "envelope") dissolves. Interphase's chromatin tightly coils and condenses until it becomes chromosomes. These chromosomes are made up of two genetically identical sister chromatids that are joined together by a centromere. Centrosomes move away from the nucleus in opposite directions, leaving behind a spindle apparatus.

• In metaphase, motor proteins found on either side of the chromosomes' centromeres help move the chromosomes according to the pull of the opposing centrosomes, eventually placing them in a vertical line down the center of the cell; this is sometimes known as the metaphase plate or spindle equator.

• The spindle fibers begin to shorten during anaphase, pulling the sister chromatids apart at their centromeres. These split chromosomes are dragged toward the centrosomes found at opposite ends of the cell, making many of the chromatids briefly appear "V" shaped. The two split portions of the cell are officially known as "daughter chromosomes" at this point in the cell cycle.

• Telophase is the final phase of mitotic cell division. During telophase, the daughter chromosomes attach to their respective ends of the parent cell. Previous phases are repeated, only in reverse. The spindle apparatus dissolves, and nuclear membranes form around the separated daughter chromosomes. Within these newly formed nuclei, the chromosomes uncoil and return to a chromatin state.

• One final process—cytokinesis—is required for the daughter chromosomes to become daughter cells. Cytokinesis is not part of the cell division process, but it marks the end of the cell cycle and is the process by which the daughter chromosomes separate into two new, unique cells. Thanks to mitosis, these two new cells are genetically identical to each other and to their original parent cell; they now enter their own individual interphases.

Stages of Meiosis

There are two primary meiosis stages in which cell division occurs: meiosis 1 and meiosis 2. Both primary stages have four stages of their own. Meiosis 1 has prophase 1, metaphase 1, anaphase 1, and telophase 1, while meiosis 2 has prophase 2, metaphase 2, anaphase 2, and telophase 2. Cytokinesis plays a role in meiosis, too; however, as in mitosis, it is a separate process from meiosis itself, and cytokinesis shows up at a different point in the division.

Meiosis I vs. Meiosis II

See a detailed comparison of Meiosis I and Meiosis II.

In meiosis 1, a germ cell divides into two haploid cells (halving the number of chromosomes in the process), and the main focus is on the exchange of similar genetic material (e.g., a hair gene; see also genotype vs phenotype). In meiosis 2, which is quite similar to mitosis, the two diploid cells further divide into four haploid cells.

Stages of Meiosis I

• The first meiotic phase is prophase 1. As in mitosis, the nuclear membrane dissolves, chromosomes develop from the chromatin, and the centrosomes push apart, creating the spindle apparatus. Homologous (similar) chromosomes from both parents pair up and exchange DNA in a process known as crossing over. This results in genetic diversity. These paired up chromosomes—two from each parent—are called tetrads.

• In metaphase 1, some of the spindle fibers attach to the chromosomes' centromeres. The fibers pull the tetrads into a vertical line along the center of the cell.

• Anaphase 1 is when the tetrads are pulled apart from each other, with half the pairs going to one side of the cell and the other half going to the opposite side. It is important to understand that whole chromosomes are moving in this process, not chromatids, as is the case in mitosis.

• At some point between the end of anaphase 1 and the developments of telophase 1, cytokinesis begins splitting the cell into two daughter cells. In telophase 1, The spindle apparatus dissolves, and nuclear membranes develop around the chromosomes that are now found at opposite sides of the parent cell / new cells.

Stages of Meiosis II

• In prophase 2, centrosomes form and push apart in the two new cells. A spindle apparatus develops, and the cells' nuclear membranes dissolve.

• Spindle fibers connect to chromosome centromeres in metaphase 2 and line the chromosomes up along the cell equator.

• During anaphase 2, the chromosomes' centromeres break, and the spindle fibers pull the chromatids apart. The two split portions of the cells are officially known as "sister chromosomes" at this point.

• As in telophase 1, telophase 2 is aided by cytokinesis, which splits both cells yet again, resulting in four haploid cells called gametes. Nuclear membranes develop in these cells, which again enter their own interphases.

References

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Mitosis and meiosis are both types of cell division. Mitosis is the process by which most cells in the body divide, involves a single round of cell division, and produces two identical, diploid daughter cells.

Meiosis is the process by which gametes are produced. Meiosis involves two rounds of cell division and produces four non-identical haploid daughter cells.

What are Mitosis and Meiosis?

Mitosis and meiosis are both types of cell division. Though there are similarities between mitosis and meiosis, there are some key differences between these two processes.

Mitosis is how new body cells are produced, whereas meiosis is used to produce gametes (i.e. sperm and egg cells).

Mitosis

Mitosis is how the cells of your body reproduce. During mitosis, a diploid parent cell (i.e. a cell with two sets of chromosomes) makes a complete copy of its DNA before splitting in two. This process produces two genetically identical daughter cells and takes place across five phases.

The phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase.

Before mitosis can begin, however, the cell must replicate its DNA. This happens during interphase, which happens over stages G1, S, and G2 of the cell cycle, and is not technically part of mitosis.

The Phases of Mitosis

Prophase

The first phase of mitosis is prophase. During prophase, the cell’s chromosomes condense and become visible under a light microscope. The nucleolus (the part of the nucleus where ribosomes are made) disappears, and the mitotic spindle (a cell structure made of microtubules) begins to form.

Prometaphase

The nuclear membrane breaks down. The microtubules attach themselves to the chromosomes and begin to move them around.

Metaphase

The microtubules move the chromosomes until they are lined up along the middle of the cell. This line of chromosomes is called the metaphase plate.

Anaphase

The chromosomes are pulled apart by the microtubules. Each chromosome is separated into two, genetically identical sister chromatids, which are pulled to opposite ends of the cell.

Telophase

The sister chromatids arrive at opposite ends of the cell. A new nuclear membrane begins to form around each set of chromosomes. The chromosomes decondense, so they are no longer visible under a light microscope. The nucleolus reappears, and the mitotic spindle disappears.

Finally, the cytoplasm of the cell splits, and two new, genetically identical daughter cells are formed. This process is called cytokinesis and usually takes place during telophase.

Meiosis

Almost all of your body’s cells divide by mitosis. Meiosis is used to produce only one type of cell, and those are the gametes. During meiosis, a diploid cell divides to produce four, non-identical haploid daughter cells, each containing a single set of chromosomes. In humans, these are sperm and egg cells.

Unlike mitosis, meiosis involves two rounds of cell division. These happen across two stages: Meiosis I, and Meiosis II. Each stage of meiosis can be further divided into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

The Stages of Meiosis

Meiosis I

Like mitosis, meiosis I takes place across five stages. Before this first round of cell division begins, the cell’s DNA is replicated during the interphase of the cell cycle.

Prophase I

During prophase I, the chromosomes condense and form homologous pairs. Each homologous pair of chromosomes lines up carefully so their genes are aligned. Next, the chromosomes swap genetic material with one another, in a process known as crossing over. This ensures that each sister chromatid is no longer genetically identical.

Prometaphase I

During prometaphase I, the nuclear envelope breaks down and microtubules attach themselves to the chromosomes.

Metaphase I

The homologous chromosome pairs line up along the metaphase plate in the middle of the cell.

Anaphase I

The homologous pairs are separated by the microtubules and are pulled to opposite ends of the cell. The homologous pairs line up and are separated at random in a process known as independent segregation. This is done to further increase genetic diversity among daughter cells.

Telophase I

The chromosomes arrive at opposite ends of the cell, and the cytoplasm is split by cytokinesis.

The first round of cell division is complete. The two non-identical, haploid daughter cells now enter the second stage of meiosis.

Meiosis II

Meiosis II is very similar to the process of mitosis, except it involves two haploid cells rather than one diploid cell.

Prophase II

During prophase II, the chromosomes condense.

Prometaphase II

The nuclear envelopes are broken down and microtubules attach themselves to the chromosomes.

Metaphase II

The chromosomes line up along the metaphase plates.

Anaphase II

The chromosomes are pulled apart by microtubules. The non-identical sister chromatids are pulled to opposite ends of the cells.

Telophase II

The sister chromatids reach opposite ends of the cells. The cells are divided by cytokinesis, and four non-identical, haploid daughter cells are produced.

Mitosis vs. Meiosis: Differences and Similarities

Mitosis and meiosis are similar processes, but there are key differences between the two.

Products of Mitosis vs. Meiosis

Mitosis produces two genetically identical diploid cells, whereas meiosis produces four non-identical haploid cells.

Cell Types Involved in Mitosis vs. Meiosis

Mitosis involves the replication of somatic cells (i.e. any cells of the body that aren’t gametes), whereas meiosis is the process by which sperm and egg cells are produced.

Cell Division in Mitosis vs. Meiosis

Mitosis involves one round of cell division, whereas meiosis involves two.

Genetic Diversity in Mitosis vs. Meiosis

Mitosis produces genetically identical daughter cells, each containing a complete copy of the parent cell’s DNA. Meiosis produces four genetically non-identical daughter cells, which increases genetic variation among gametes (and, therefore, genetic diversity in the population).