Course Content
History of genetics
Learn introductory genetics with Braimy- B.Sc agriculture
About Lesson
  1. Interphase:

Interphase- Definition, Stages, Cell cycle, Diagram, Video

a) G1 Phase:

  • period between the beginning of interphase and the beginning of the DNA synthesis.
  • It is the longest phase and constitutes up to 50% of the total inter phase duration.
  • Marked events includes Marked protein and RNA synthesis, Increase the cell volume by imbibing water and nutrients

b) S Phase:

  • period between G1 and G2 phases
  • DNA synthesis takes place (chromosomes replicate)
  • RNA and protein synthesis are very low.


c) G2 Phase:

  • period between S and M phases
  • There is considerable amount of RNA and protein synthesis takes place in this phase.

  1. M phase:

a) Interphase:

  • Structural and functional protein is synthesized.
  • RNA and ribosomes are synthesized.
  • DNA of each chromosome replicates.
  • Cell volume increases.
  • Division of mitochondria and chloroplast.
  • Doubling of centrioles
  • High cell metabolic rate

b) Prophase:

  • Uncoiling of chromatids
  • Disintegration of nucleolus
  • Disappearance of nuclear membrane
  • Formation of spindle

Cytokinesis Images – Browse 781 Stock Photos, Vectors, and Video | Adobe  Stock

c) Metaphase:

  • Arrangement of chromosome on equilateral region.

Metaphase - Wikipedia

d) Anaphase:

  • Splitting of centromere or division of chromosome.
  • Movement of chromosomes to opposite poles.

Anaphase - Wikipedia

e) Telophase :

  • Formation of daughter nuclei
  • Reappearance of nuclear membrane and nucleolus.

File:Telophase.svg - Wikimedia Commons

  1. Meiosis I:

A) Prophase I: Homologous chromosomes pairing (Synapsis) and crossing over (Recombination) occurs.

Explain the stages of prophase I of meiosis.

a) Leptotene: These cells and nuclei are usually bigger than the other cells, like a “bouquet”

b) Zygotene: Pairing of homologous chromosomes begins. It is also called synapsis and the resulting structure synaptic complex

c) Pachytene: The pairing stabilizes. The number of synaptic complexes corresponds to the number of chromosomes in a haploid set of the respective species. The pairs are also called bivalents.

d) Diplotene: The bivalents separate and formed cross-like structures, single or multiple loops: the chiasmata (sing. chiasma).

e) Diakinesis: The chromosomes condense and become more compact.

B) Metaphase I: Bivalents are randomly oriented along the metaphase plate.

Metaphase in Mitosis and Meiosis (Metaphase 1 and 2)

C) Anaphase I:

  • Kinetochore microtubules shorten and pull chromosome towards opposite poles forming two haploid chromosomal sets.
  • Non-kinetochore microtubules lengthen pushing the centrioles apart and the cell elongates.

Anaphase in Mitosis and Meiosis (Anaphase I, II) - The Biology Notes

D) Telophase I:

  • Microtubules disappears, new nuclear membrane surrounds each haploid set
  • Chromosomes uncoil and cytokinesis occurs.

Meiosis: Telophase l | Mitosis and Meiosis and the Cell Cycle - passel

E) Interkinesis: Rest period of cell and hence no DNA replication occurs during this stage.

4. Meiosis II

  • Results in formation of 4 haploid cells.

Meiosis II | Definition, Examples, Diagrams

a) Prophase II:

  • Disappearance of nucleoli and the nuclear envelope.
  • Shortening and thickening of chromatids.
  • Centrioles moves to the polar regions and arrange spindle fibers for the second meiotic division.

b) Metaphase II:

  • Metaphase equatorial plate is rotated by 90 degrees when compared to meiosis I.

c) Anaphase II:

  • Microtubules pull the sister chromatids towards opposite poles.

d) Telophase II:

  • Uncoiling and lengthening of the chromosomes and the disappearance of spindle fiber.
  • Nuclear envelops reform and cleavage and produces four daughter cells.
Join the conversation
Scroll to Top