Question

1.- What are the principal characteristics on Prophase I (one) ? ____________________

2.- In mitosis, cells with 24 chromosomes, produce daughter cells with _________________ chromosomes.

3.- When in mitosis, the chromosomes are lined up in a central plane? __________________.

4.- What are the cell-cycle checkpoints? _________________

Thank you.

Answer 1

1. It is divided into 5 stages, each characterised by different features as given below -

2. There are two types of cell divisions - mitosis which is called as equational division and meiosis which is called as reductional division. In mitosis the number of chromosomes in the parental cell and daughter cells are equal to each other and hence, it is called equational division. In the question, it is given that there are 24 chromosomes in the parental cell, so in the daughter cells, after mitosis, there will be 24 chromosomes.

3. During mitosis, third phase is called metaphase and is characterized by the presence of chromosomes being aligned at a central plane. This central plane is called metaphysic plate or equatorial plate. In this phase all the chromosomes are present at the equator of cell and are suspended in the middle with the help of spindle fibres which emerge from centrioles located at the pole of the cell.

See image below -

4. Cell cycle checkpoints are control or checkpoints which check the transition to next phase of the cell cycle.

For details see the image below -

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