Name: meiosis ii in gamete formation
Uploaded: 2021-04-07T12:12:02.000Z
Duration: 2 min 2 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-4

Meiosis II

Meiosis II is the second cell division of meiosis, which can either start immediately after meiosis I,&#160; without any prior DNA synthesis, or, after a brief time interval called interkinesis.
Like mitosis, meiosis II follows an equational division, except in meiosis II, a haploid cell gets divided into two haploid cells.
Meiosis II&#160; is divided into four stages &#8211; prophase II, metaphase II, anaphase II, and telophase II.
Prophase II is characterized by the thickening and shortening of the chromosomes. Centrioles move to opposite poles and begin to form a meiotic spindle which is followed by the dissolution of the nuclear membrane.
In metaphase II, the chromosomes line up at the equatorial plane of the cell. Unlike in mitosis, the sister chromatids constituting each chromosome are non-identical&#160; as they underwent recombination in meiosis I.&#160;
In anaphase II, the cohesin complex that holds the two sister chromatids together, breaks down, allowing single chromatids to move towards opposite poles.
Like homologous chromosomes in meiosis I, these sister chromatids also undergo independent assortment and contribute to the production of the genetically unique gametes.
Telophase II is marked by

meiosis ii

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila, and mice, the meiotic spindle forms without centrosomes. Further, in mammalian oocytes, cyclin A2 plays a vital role in the stabilization of the meiotic spindle and the separation of the sister chromatids in anaphase II. In mouse oocytes, inhibition of cyclin A2 results in disordered spindle formation and failure of segregation of sister chromatids.
Telophase II is followed by cytokinesis, which completes one meiosis cycle with the production of four haploid daughter cells. In male meiosis, all four daughter cells have equal amounts of cytoplasm; however, in female gametes, asymmetric distribution of the cytoplasm occurs in meiosis I, which leads to the production of an egg cell and a haploid polar body. The egg cell undergoes meiosis II only after fertilization and produces the haploid mature ovum and the secondary polar body. The mature ovum then fuses with the sperm and forms the diploid zygote.

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for ...

Education

JoVE Core

Molecular Biology

Unit 2

Meiosis

KEY TERMS AND CONCEPTS

meiosis ii in gamete formation

Meiosis II is the second cell division in meiosis and it separates sister chromatids. This division turns haploid cells into four unique haploid gametes. Its stages are similar to mitosis, but meiosis II happens in haploid cells, while mitosis happens in diploid cells.

The timing of meiosis II is different in males and females. In male meiosis, centrosomes help form the meiotic spindle. In oocytes from humans, Drosophila, and mice, the spindle forms without centrosomes. In mammalian oocytes, cyclin A2 helps stabilize the spindle and supports sister chromatid separation during anaphase II. In mouse oocytes, blocking cyclin A2 can cause disordered spindle formation and a failure to separate sister chromatids.

Meiosis II ends with telophase II and cytokinesis. These steps complete one meiosis cycle and produce four haploid daughter cells. In male meiosis, the four daughter cells receive equal amounts of cytoplasm. In female gametes, cytoplasm is divided unevenly during meiosis I, which produces an egg cell and a haploid polar body.

In females, the egg cell completes meiosis II only after fertilization. This division produces the haploid mature ovum and the secondary polar body. The mature ovum then fuses with sperm to form a diploid zygote.

Meiosis II in Gamete Formation

what is meiosis?

Meiosis and the Making of Gametes

Meiosis is the cell division process that makes gametes, or sex cells. It uses one round of DNA replication followed by two divisions. The result is cells with half the usual number of chromosomes. This process matters because it prepares cells for sexual reproduction. It also helps maintain the correct chromosome number when sperm and egg combine. In many organisms, meiosis is a key step in forming haploid cells.

meiosis i

Homolog Pairing and Recombination in Meiosis I

Meiosis I is the stage of meiosis when homologous chromosomes pair, exchange DNA, and reduce the chromosome number by half. It helps form haploid sperm and eggs in animals through cell differentiation. This first division is the step that separates the two sets of chromosomes. Prophase I is the longest and most complex part of meiosis I. During this stage, homologous chromosomes undergo synapsis, which means they pair closely together. The synaptonemal complex, a protein structure, helps make...

Meiosis II is the second cell division in meiosis and it separates sister chromatids. This division turns haploid cells into four unique haploid gametes. Its stages are similar to mitosis, but meiosis II happens in haploid cells, while mitosis happens in diploid cells. The timing of meiosis II is different in males and females. In male meiosis, centrosomes help form the meiotic spindle. In oocytes from humans, Drosophila, and mice, the spindle forms without centrosomes. In mammalian oocytes,...

crossing over

Crossing Over in Meiosis

Crossing over is an important step in meiosis. It happens during prophase I, when homologous chromosomes pair up closely. This pairing lets matching DNA segments exchange places. The exchange occurs between non-sister chromatids of homologous chromosomes. The result is a new combination of genetic material. This process helps create genetic variation in the cells that are formed. Crossing over works together with chromosome pairing and separation during meiosis. It is a key reason offspring...

meiosis vs. mitosis

Mitosis and Meiosis Differences

Mitosis and meiosis are cell division processes with different jobs in the body. Mitosis supports growth and development by dividing somatic cells. Meiosis divides germ cells and is essential for sexual reproduction. Before mitosis and before meiosis I, the cell copies its DNA. This creates two homologous copies of each chromosome. High cyclin-dependent kinase, or CDK, activity then blocks DNA synthesis by stopping pre-replicative complex formation. That is why DNA replication does not begin...

nondisjunction

Chromosome Segregation Errors

Nondisjunction is a chromosome segregation error during cell division. It happens when chromosomes do not separate the way they should. This mistake can affect the chromosome number in the cells that are formed. The error can occur during meiosis or mitosis. In meiosis, nondisjunction may lead to gametes with too many or too few chromosomes. In mitosis, it can affect body cells after division. These changes can disrupt normal chromosome balance. Nondisjunction is an important idea in genetics...

key terms and concepts

Learn how meiosis II separates sister chromatids, forms haploid gametes, and differs in male and female cells, including spindle changes after fertilization.

Meiosis II in Gamete Formation | JoVE K12

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Meiosis II in Gamete Formation

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