A Cell Preparing To Undergo Meiosis Duplicates Its Chromosomes During?
Meiosis is a special type of cell division used to produce gametes (sperm and egg cells) in sexually reproducing organisms. It produces four daughter cells with only half the chromosomes of the parent cell.
A cell preparing to undergo meiosis duplicates its chromosomes during a special round of DNA replication called the S phase. Each homologous pair of chromosomes is duplicated to form two identical sister chromatids, held together by cohesin proteins at the centromere.
Prophase I
During prophase I, a cell prepares to undergo meiosis (which splits the chromosomes producing two daughter cells). In prophase I, chromatin fibers become more dense and compact, and the chromosomes are condensed into sister chromatids’ that are very close together. These are called sister chromatids because they contain identical chromosomes attached to the centromere.
The nucleolus is also disassembled, and the Golgi apparatus and endoplasmic reticulum are rearranged in the cell. These structures are important in creating the ribosomes that transcribe RNA into proteins. They are essential to the process of meiosis itself because they will be reassembled after the division is complete and in each new cell.
At the beginning of prophase, a membrane around the nucleus dissolves away to allow the chromosomes to be easily accessed. Once the chromosomes are accessible, they move toward opposite poles of the cell.
When the chromosomes reach the opposite poles, they attach to centrosomes, groups of microtubules that are essential in mitotic spindle assembly. These are surrounded by an aster of radially arranged fibrils, which extend between the centrosomes to form the spindle.
The spindle consists of a central hub, called the kinetochore, that is anchored to the chromosome, and microtubules that extend from the kinetochore and attach to the chromosome at the cis-acting end. In mitotic and meiotic cell division, changes in the length of these microtubules are critical to chromosome movement.
In meiosis, a chromosome’s sister chromatids are linked by a complex protein called cohesin. When the cohesin breaks down, each chromosome separates from its sister and moves to opposite poles of the cell. The chromosomes will continue to move and separate throughout meiosis as they are pulled apart by changes in microtubule length.
Homologous chromosomes pair with each other and may undergo genetic recombination during meiosis I to exchange some of their DNA. These recombination events produce physical links called ‘chiasmata’ between the homologous chromosomes, which can help the cells segregate during meiosis I (Snustad and Simmons, 2015).
Once the chiasmata have moved toward the ends of their respective chromatids, they begin to drift apart. This process of separation, called diakinesis, is a critical step in the final stage of meiosis I and meiosis II.
Meiosis II is a similar process to meiosis I, but instead of separating the chromatids into haploid daughter cells, it produces two euploid daughter cells, each with 23 chromosomes. This is because each chromosome’s recombination events have produced additional copies of itself.
This extra copy of DNA is then extruded into polar bodies in the daughter cells. This excess DNA is responsible for a phenomenon known as genetic redundancy, whereby there can be more than one allele in the gene that causes a particular trait to occur in the cell.
The recombination events in meiosis II are similar to those in meiosis I, but they do not occur as often, and they are more complicated. Meiosis II is a more complex process and can be harder for cells to replicate.
A Cell Preparing To Undergo Meiosis Duplicates Its Chromosomes During? A Better Guide To Know
Meiosis is the process of cell division that occurs in sexually reproducing organisms, leading to the production of haploid gametes (sperm and eggs). The process involves two rounds of cell division, known as meiosis I and meiosis II, which result in the production of four genetically diverse daughter cells.
Before a cell can undergo meiosis, it must prepare by duplicating its chromosomes during interphase, which precedes the first round of meiotic division. During interphase, the cell undergoes DNA replication, in which each chromosome is duplicated to form two identical sister chromatids joined together by a centromere. This results in a cell with twice the number of chromosomes, a diploid cell.
The duplicated chromosomes condense and become visible as distinct structures during prophase I, the first stage of meiosis I.
Homologous chromosomes pair up to form bivalents consisting of four chromatids and undergo a process called synapsis, in which they exchange segments of DNA through a process called crossing over. This genetic exchange results in the creation of new combinations of alleles, increasing genetic diversity.
In metaphase I, the bivalents line up along the cell’s equator, with spindle fibers attached to the centromeres. The orientation of each bivalent is random, further contributing to genetic diversity. During anaphase I, the homologous chromosomes separate, with each pair of sister chromatids pulled toward opposite poles of the cell.
Telophase I and cytokinesis follow, resulting in the formation of two haploid daughter cells, each containing one set of chromosomes, with each chromosome consisting of two sister chromatids. The daughter cells are genetically unique from each other and the parent cell due to the crossing over and random orientation of bivalents during meiosis I.
Meiosis II is similar to mitosis, consisting of prophase II, metaphase II, anaphase II, telophase II, and cytokinesis. In prophase II, the spindle apparatus forms, and the chromosomes condense. In metaphase II, the chromosomes line up along the cell’s equator, and spindle fibers attach to the centromeres. During anaphase II, the sister chromatids separate and are pulled toward opposite poles of the cell.
In telophase II and cytokinesis, the nuclear envelope reforms, the chromosomes decondensed, and four haploid daughter cells are formed, each containing one set of chromosomes consisting of a single chromatid. These daughter cells are genetically unique due to the crossing over and random orientation of bivalents during meiosis I and the independent assortment of chromosomes during meiosis II.
In summary, a cell preparing to undergo meiosis duplicates its chromosomes during interphase, resulting in a diploid cell. During meiosis I and II, the cell undergoes two division rounds, producing four genetically diverse haploid daughter cells. The process involves the pairing and exchange of genetic material between homologous chromosomes during meiosis I and the separation of sister chromatids during meiosis II. Meiosis contributes to genetic diversity and is essential for sexual reproduction in eukaryotic organisms.
FAQ’s
What does meiosis start with a diploid cell?
First off, despite the fact that meiosis begins with a diploid cell (a parent egg or spermatocyte), its final result is a set of four haploid daughter cells, each of which has 23 chromosomes.
What does a diploid cell produce after meiosis?
Haploid gametes are produced by meiosis. At fertilisation, male and female gametes combine to create a zygote, which grows into a new life, and reestablish diploidy. Diploid cells undergo meiosis at the time of sex maturation, which results in the creation of haploid gametes.
What is the product of meiosis?
The results of meiosis, four haploid cells with only one chromatid on each chromosome, are produced by cytokinesis, which divides the chromosome sets into new cells. Sperm or egg cells are the byproducts of meiosis in humans.
What does meiosis produce?
A single cell splits twice during the meiotic process, resulting in four cells with half the original genetic material. These cells—sperm in men and eggs in women—are our sex cells.
Is the product of meiosis diploid?
Four haploid daughter cells with chromosomal variations from the original parent cell and half as many chromosomes as the original parent cell are the result of meiosis (diploid).
