Question

For each of the following cells indicated in the image, say which phase of the cell cycle they are in. If they're in mitosis, be specific about which phase. You don't need to be specific about which part of interphase they're in. Cell A: Cell B: Cell C: Cell D: Cell E:

Answer 1

Mitosis is called equational division. It occurs in somatic cells where each cell becomes two. This is initiated by replication of the DNA where 2 copies of the entire chromosome is made and it is then sent to both the daughter cells.

The cell cycle is divided into G1, S, G2 and M phase. The G1 is the first growth phase where the cell prepares for replication and all cell contents are duplicated.S phase where the DNA is replicated and 2 copies are made.G2 phase where the cell grows rapidly and all the proteins needed for the cell are made. M phase is the phase where division of the cell occurs.It can be mitosis or meiosis. IN mitosis, there are 5 stages-

interphase- it is the 1st stage of mitosis, where the cell is getting prepared for division. the chromosomes are still intact. microtubules begin to extend from the centrosomes. usually this stage is not considered in mitosis. chromosomes are still in thread shaped.

prophase- Here the chromosomes begin to condense and each chromosome has 2 sister chromatids.the nuclear membrane begins to disappear.centrioles begin to setup across the ends of the cell.Spindle fibers begin to appear.

metaphase- here the chromosomes appear in a straight line at the centre of the cell.The centromeres are attached to the centrioles through their kinetocores by the spindle fibres. each sister chromatid are attached through the spindle fibres to their respective poles.

anaphase- this is the phase where the sister chromatids will be pulled to the opposite poles.each chromatid of the chromosome are pulled to the opposite poles.the cell also starts to pull apart and elongate.these microtubules are all controlled by motor proteins.

telophase- this is the last phase of mitosis where all the chromosomes gather at one end of the cell. the cell begins to pinch at the centre and form a bridge.the chromosomes once again assume their original thread like structures and the nuclear membrane begins to form again along with the nucleolus. two nuclei are formed at the end. Cytokinesis is followed after telophase where the cytoplasm divides between the 2 spaces and the cell plate is formed between both of them forming 2 daughter cells.The end is the formation of 2 cells both with equal DNA and other contents.

IN the given picture- the stage of mitosis can be identified using the above characteristics.

Cell A - Interphase. This is the stage where the cell is yet to enter mitosis. the chromosomes are still not condensed and the entire mass can be seen.

Cell B - Anaphase. As it can be seen that the chromosomes are being pulled apart to the opposite poles.

Cell C - Metaphase. The chromosomes can be seen at the equatorial plate arranged at the centre of the cell.

Cell D - Interphase. but it is slightly under the phase between interphase and the prophase. Because the chromosome condensation is not yet clear but it is beginning to enter prophase. Hence it can be called late interphase or early prophase.

Cell E - Prophase. The condensation of the chromosomes can be seen. Hence it is prophase.