Question

Draw the stages of meiosis and briefly explain what is happening in each stage and then create a table or list that compares the stages of mitosis and meiosis.

Answer 1

MEIOSIS - 1

◆ karyokinesis -1

● prophase :- 1

• Leptotene :-
  • ​​​​nuclear membrame start disappearing .
  • Centriole start moving towards pole.
  • Chromosome have 2 thread but fitted as they are one .
• Zygotene :-
  • ​​​​​​​chromosome synapse is accompanied by the formation of synaptonemal complex .
  • On account of synapsis , chromosome form pairs of bivalent .
• Pachytene :-
  • The synaped chromosome become short and thick .
  • The chromatin of each chromosome slightly seprate and become visible .
  • The two visible chromatins of a chromosome are called dyad .
  • The group of 4 homologous chromatin is called dyads ( tetrads ) .
  • The moon sister chromatins of homologous start crossing each other .
• Diplotene :-
  • ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​the non sister chromatin of homologous stick at the point of crossing over , those points are called chiasmata .
  • The homologous chromosome start separate from each other . The process is called disjunction .
  • This make chromatin clearly visible but sepration of homologous chromosome does not take place at chiasmata where crossing over occur during pachytene .
• Diakinesis :-​​​​​​​​​​​​​​​​​​​​​
  • Chiasmata shift towards the ends of the chromosomes . The phenomenon is called terminalisation .
  • The chromosome are fully condensed at the meiotic spindle is assembled to prepare the homologous chromosome for sepration .
  • The nucleolus and nuclear envelop disintegrate .

● Metaphase - 1

• all the homologous chromosomes pair come at the center of cellat equitorial line and get septated .

● Anaphase:1

• The spindle fibre start shrinkage due to condensation which ultimately split the centre .
• The seprated chromosome move to opposite pole and the space become large between two separated chromosome pair .

● Telophase -1

• ​​​​​​​the polar group of chromosome arrange themselves into haploid and dyad nuclei .
• A nucleolus is formed followed by the appearance of nucleoplasm and nuclear enevelop .

◆ Cytokinesis -1

• nuclear membrame reappeared completely .
• Two daughter cells are formed .

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MEIOSIS - 2

◆ Karyokinasis - 2

● Prophase - 2

• the most of case , prophase 2 is absent and cells directly enter into metaphase 2

● Metaphase -2

• The chromosome align at the equator and the microtubules form opposite poles of the spindle get attached to the kinetochores of sister chromatids .

● Anaphase - 2

• the centromere of each chromosome divides into two .

● Telophase - 2

• the four groups of chromosome separates completely
• Nuclear membrane starts reappearing .

◆ Cytokinesis - 2

• the nuclear membrane appears completely .
• Two daughter cells are formed .

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