The upcoming discuss will update you about the differences between meiosis and mitosis.
Difference # Meiosis:
Characteristic:
i. Location:
Reproductive tissues only.
ii. Shape of Cells:
Usually spherical.
iii. Daughter Cells:
a. On completion of meiosis four daughter cells are produced from one cell.
b. Chromosome number of daughter cells is half of that of the parent cell.
iv. Genetic Variation:
Generates genetic variability because, of segregation and recombination.
v. S phase:
a. Occurs only in the premeiotic interphase; there is no S phase in the interphase following the first division of meiosis.
b. About 0.3% of the DNA is not replicated during S phase.
vi. Number of Nuclear Divisions:
After the premeiotic S phase, nucleus undergoes two divisions.
vii. First Prophase:
a. Homologous chromosomes pair. As a result, only n chromosome pairs can be seen. There is crossing over between homologous chromosomes, and chiasmas are observable.
b. About 0.3% of the DNA is syntesized during zygotene and pachytene.
viii. Second Prophase:
a. Chromosome number is only n.
b. Relational coiling between sister chromatids is absent. Chromosomes are highly condensed and small from the very beginning.
c. It is of relatively short duration.
ix. First Metaphase:
a. Homologous chromosomes are paired to form bivalents.
b. The number of bivalents (chromosomes pairs) is n. Centromeres of the chromosomes lie on the either side of equilateral plate. Each bivalent has four chromatids.
x. Second Metaphase:
a. The chromosome number is n.
b. Repulsion between sister chromatids is clearly visible from prophase itself.
c. Chromosomes are much smaller.
xi. Anaphase:
a. Homologous chromosomes from each bivalent move to the opposite poles.
b. Centromeres do not divide.
xii. Second Anaphase:
a. Chromosome number is n.
b. In all the stages of second meiotic division, two nuclei divide in one parent cell.
xiii. First Telophase and Cytokinesis:
a. Chromosomes do not uncoil completely.
b. In some species, cytokinesis does not take place.
c. Cytokinesis includes membrane formation, and middle lamella is not deposited.
d. In certain species, first telophase and the following interphase are absent.
e. Each cell gives rise to four haploid cells; the resulting structure is called tetrad.
f. Daughter cells are n.
g. Daughter cells usually differentiate into spares/ gametes.
Difference # Mitosis:
Characteristic:
i. Location:
Somatic and reproductive tissues.
ii. Shape of Cells:
Generally rectangular.
iii. Daughter Cells:
a. One cell produces two daughter cells.
b. Chromosome number of daughter cells is the same as that of the parent cell.
iv. Genetic Variation:
Maintains genetic uniformity among daughter cells.
v. S phase:
a. Exists in every interphase.
b. The total DNA present in a nucleus is replicated during S phase.
vi. Number of nuclear divisions:
Each nucleus divides once after every S phase.
vii. First prophase:
a. Homologous chromosomes do not pair: 2n chromosome number may be seen.
b. There is no crossing over between homologous chromosomes, and chiasma cannot be seen.
c. There is no DNA synthesis.
viii. Second prophase:
a. Chromosomes are 2n in number.
b. Sister chromatids show relational coiling. In early prophase, chromosomes are very long; later they become smaller due to progressive condensation.
c. It is quite long in duration.
ix. First Metaphase:
a. Each chromosome is unpaired.
b. 2n chromosomes are clearly seen.
c. Centromeres of the entire chromosome lie on the equatorial plate.
d. Each chromosome has two chromatids.
x. Second Metaphase:
a. The number of chromosomes is 2n.
b. The two sister chromatids of a chromosome do not exhibit repulsion.
c. Chromosomes are relatively longer.
xi. Anaphase:
a. The two sister chromatids (of each chromosomes) move to the opposite poles.
b. Centromere of each chromosome divides longitudinally.
xii. Second Anaphase:
a. Chromosomes number is 2n.
b. Generally, a single nucleus divides in a cell.
xiii. First Telophase and Cytokinesis:
a. Chromosomes almost completely uncoil.
b. In all the species, cytokinesis takes place.
c. Cytokinesis involves the formation of middle lamella and primary cell wall.
d. Telophase and interphase are found in all species.
e. Each cell produces two daughter cells.
f. Daughter cells are 2n.
g. Daughter cells generally differentiate as body cells.
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