Explain the different stages of mitosis along with a diagram
Answers
Explanation:
Mitosis is a continuum of changes but biologists like break down the stages of mitosis into four main stages, prophase, metaphase, anaphase and telophase.
The focus in this class is on an understanding of the process and not memorization of phases.
The only phase name you will need to remember is metaphase.
In mitosis the nuclear membrane is broken down, spindle fibres (microtubules) attach to the chromatids at the centromere and pull apart the chromatids.
When the chromatids reach separate ends of the cells, the spindle fibres disintegrate, and a nuclear membrane rebuilds around the chromosomes making two nuclei.
Each nucleus is identical to the original nucleus as it was in G1.
Also read: Significance of Mitosis
Meiosis
Meiosis is the form of nuclear cell division that results in daughter cells that have one half the chromosome numbers as the original cell.
In organisms that are diploid, the end result is cells that are haploid. Each daughter cell gets one complete set of chromosomes, i.e., one of each homologous pair of chromosomes.
In humans, this means the chromosome number is reduced from 46 to 23.
The only cells that undergo meiosis will become sperm or eggs.
The joining together of a sperm and egg during fertilization returns the number of the chromosomes to 46.
Cells that undergo meiosis go through the cell cycle including the S phase so begin the process with chromosomes that consist of two chromatids just as in mitosis.
Meiosis consists of meiosis I and meiosis II. In meiosis I homologous chromosomes are separated into different nuclei.
This is the reduction division; chromosome number is cut in half. Meiosis II is very similar to mitosis; chromatids are separated into separate nuclei.
As in mitosis, it is spindle fibres that “pull” the chromosomes and chromatids apart.
The end result of meiosis is four cells, each with one complete set of chromosomes instead of two sets of chromosomes.
Also read: Significance of Meiosis
Let us have a look at some important difference between mitosis and meiosis.
Difference Between Mitosis and Meiosis
Difference Between Mitosis And Meiosis
Difference Between Mitosis And Meiosis
The important difference between mitosis and meiosis are mentioned below:
Difference between Mitosis and Meiosis
Types Mitosis Meiosis
Interphase Each chromosome replicates. The result is two genetically identical sister chromatids. Interphase – Chromosomes not yet visible but DNA has been duplicated or replicated.
Prophase Prophase I – crossing-over recombination – Homologous chromosomes (each consists of two sister chromatids) appear together as pairs. Tetrad is the structure that is formed. Segments of chromosomes are exchanged between non-sister chromatids at crossover points known as chiasmata (= crossing-over). Prophase –Each of the duplicated chromosomes appears as two identical or equal sister chromatids, The mitotic spindle begins to form. Chromosomes condense and thicken.
Metaphase Metaphase I Chromosomes adjust on the metaphase plate. Chromosomes are still intact and arranged as pairs of homologues. Metaphase -The chromosomes assemble at the equator at the metaphase plate.
Anaphase Anaphase I Sister chromatids stay intact. But homologous chromosomes drift to the opposite or reverse poles. Anaphase – The spindle fibres begin to contract. This starts to pull the sister chromatids apart. At the end of anaphase, a complete set of daughter chromosomes is found each pole.
Mode of Reproduction Asexual Reproduction. Sexual Reproduction.
Occurs in Eukaryotic cells. Diploid cells.
Function General growth and repair, Cell reproduction Genetic diversity through sexual reproduction.
Cytokinesis Occurs in Telophase. Occurs in Telophase I and in Telophase II.
Karyokinesis Occurs in Interphase. Occurs in Interphase I.
Discovered by Walther Flamming. Oscar Hertwig.
Explanation:
These stages are prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have already duplicated, condense and attach to spindle fibers that pull one copy of each chromosome to opposite sides of the cell. The result is two genetically identical daughter nuclei.