Question

• What are the differences between mitosis and meiosis?

Answer 1

The process of parent cell divide into two or more daughter cells is called a cell division.cell division is of two types, mitosis and meiosis.

Mitosis is the process of dividing cell into two or more daughter cells without changing its ploidy, it is the common cell division taking place in the body.Both diploid and haploid cells can undergo mitosis. If a haploid cell undergoes mitosis, which is something certain types of plant and fungus do as part of their normal life cycles, the end result is two identical haploid cells (n→n).

During mitosis, a eukaryotic cell undergoes a carefully coordinated nuclear division that results in the formation of two genetically identical daughter cells.Then, at a critical point during interphase (called the S phase), the cell duplicates its chromosomes and ensures its systems are ready for cell division.

Commonly,mitosis is preceded by the S stage of interphase (during which the DNA is replicated) and is often accompanied or followed by cytokinesis, which divides the cytoplasm, organelles and cell membrane into two new cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of an animal cell cycle,the division of the mother cell into two daughter cells genetically identical to each other.

There are four stages of mitosis,they are:- prophase, metaphase, anaphase, and telophase.

prophase:-It is the first and longest phase of mitosis. During prophase, chromatin condenses into chromosomes, and the nuclear envelope, or membrane, breaks down. In animal cells, the centrioles near the nucleus begin to separate and move to opposite poles (sides) of the cell.

During late prophase the mitotic spindle begins to capture and organize the chromosomes. The chromosomes finish condensing, hence they looks as very compact structure. The nuclear envelope breaks down, releasing the chromosomes.Prophase is important because this is when chromatin becomes chromosomes so the right number of chromosomes can be distributed equally to each daughter cell produced.

metaphase:-During metaphase, Chromosomes line up at the metaphase plate, under tension from the mitotic spindle. The two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles. the spindle has captured all the chromosomes and lined them up at the middle of the cell, ready to divide.In the metaphase cell, there are 4 chromosomes (8 chromatids) total and two sets of homologous chromosomes that are duplicated. In the anaphase cell, there are 8 chromosomes. The resulting daughter cells will also be diploid and genetically identical to the mother cell.Metaphase takes about 4 percent of the time required for the completion of a cell cycle.

Anaphase:- Anaphase is the fourth phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. ... The separated chromosomes are then pulled by the spindle to opposite poles of the cell.Sister chromatids separate, and the now-daughter chromosomes move to opposite poles of the cell. ... Anaphase begins when the duplicated centromeres of each pair of sister chromatids separate, and the now-daughter chromosomes begin moving toward opposite poles of the cell due to the action of the spindle.

Anaphase is a very important stage of cell division. It ensures that duplicated chromosomes, or sister chromatids, separate into two equal sets. This separation of chromosomes is called disjunction. Each set of chromosomes will become part of a new cell.

If you view early anaphase using a microscope, you will see the chromosomes clearly separating into two groups. If you are looking at late anaphase, these groups of chromosomes will be on opposite sides of the cell.

Telophase:- Telophase is the fifth and final phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. Telophase begins once the replicated, paired chromosomes have been separated and pulled to opposite sides, or poles, of the cell.During telophase, the nuclei for the daughter cells finally form and the cell begins to split into two. Meiosis is the process that leads to the formation of sperm cells and egg cells.

Cytokinesis occurs right after telophase.During cytokinesis, the cytoplasm divides along with the organelles. At the end of cytokinesis, two new daughter cells form.

Meiosis:-

Meiosis generally occurs in the sec cells of the body.Sex cells or gamet cells are the sperm in males, eggs in females. During meiosis one cell? divides twice to form four daughter cells.

There are 8 stages in the meiosis, they are:-prophase I,Metaphase I,Anaphase I,Telophase I and Cytokinesis,Prophase II,Metaphase II,Anaphase II, Telophase II and Cytokinesis.

Prophase I:- the crossing over and recombination of genetic material between non sister chromatids occurs during prophase i,this results in the genetically unidentical, haploid daughter chromatid cells.

Metaphase I:- In metaphase I, the two chromosomes of a homologous pair face opposite poles. ... This means that the resulting two cells (produced during cytokinesis at the end of meiosis I) will contain full sets of chromosomes, but these will not consist of chromosome pairs.

Anaphase I:- Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle. Notice that in anaphase I the sister chromatids remain attached at their centromeres and move together toward the poles.

Telophase I:- The homologous chromosome pairs reach the poles of the cell, nuclear envelopes form around them, and cytokinesis follows to produce two cells. ... The homologous chromosome pairs complete their migration to the two poles as a result of the action of the spindle.

ProphaseII:-Prophase I is divided into five phases:leptotene, zygotene, pachytene, diplotene, and diakinesis.

The leptotene stage, also known as the leptonema, is the first of five substages of prophase I in meiosis. The term leptonema derives from Greek words meaning "thin threads". ... At the transition to the zygotene stage the telomeres usually aggregate at a nuclear envelope sector, thereby forming a meiotic bouquet.

The zygotene is the stage of prophase I that follows after leptotene and precedes pachytene. Prior to zygotene, the chromosomes start to condense into long strands inside the nucleus and the chromosomes appear as threadlike. Zygotene is that phase wherein the homologous chromosomes pair or come together in synapse.

Pachytene, also referred to as pachynema, is one of the five sub stages of Prophase I in meiosis. It is the third sub stage following leptotene and zygotene and preceding diplotene and diakinesis, beginning after synapsis is complete. Pachytene is defined as the stage when a fully formed synaptonemal complex exists.

During diplotene the CHROMATIDS become separated (except at the CHIASMATA), and the chromosomal material is contracting. The chiasmata indicate that CROSSING OVER is taking place.

During diakinesis, the chromosomes condense, the nucleolus fragments and the nuclear envelope disperse Supplement Meiosis is form of cell division that gives rise to genetically diverse sex cells or gametes.

Metaphase II:-In metaphase II, the second stage of meiosis II, in each of the two daughter cells produced by the first meiotic division (which are known as secondary germ cells), the spindle again draws the chromosomes to the metaphase plate.

Anaphase II:-Anaphase II is the stage when sister chromatids of every chromosome separate and begin to move towards the opposite ends of the cell. The separation and the movement is due to the shortening of the kinetochore microtubules. Anaphase II precedes telophase II. Meiotic anaphase II is similar to the anaphase in mitosis.

Telophase II:-During telophase II, the fourth step of meiosis II, the chromosomes reach opposite poles, cytokinesis occurs, the two cells produced by meiosis I divide to form four haploid daughter cells, and nuclear envelopes followed by cytokinesis.