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Q 12.ANAPHSE 1 AND ANAPHASE 2
Key Differences
Anaphase 1 occurs in a diploid cell and counter to this anaphase two occurs in the haploid cell.
Anaphase 1 results in the separation of chromosomes, whereas anaphase 2 results in separation of two sister chromatids.
In anaphase, one centromere remains intact whereas in anaphase two centromere splits.
In anaphase one chromosomes separate to opposite pole and the sister chromatids are together, whereas in anaphase two chromosomes separate splitting the centromere and sister chromatids.
14.S PHASE AND G² PHASE
Typically, the G1 phase is the period of time in which a cell "recovers" from mitosis.
During mitosis, several organelles are disassembled and redistributed for various reasons, but primarily to ensure equal inheritance to daughter cells (see What part of the cell is actually dividing in mitosis?). A large part of G1 involves reassembling all these organelles correctly, ensuring that they are functioning properly, and synthesizing all sorts of biomolecules to ensure that the cell can grow and divide once more. In G1, cells also take some time to check whether there are sufficient nutrients in the surrounding medium to ensure that the cell cycle doesn't stall at any stage due to nutrient unavailibility. Once a cell is confident (pardon the anthropomorphization) that everything is ready, it undergoes the G1/S checkpoint to license DNA replication.
In S phase, the cell expends a lot of its energy into DNA replication. A lot of processes are active in the nucleus at this stage apart from DNA replication, such as the DNA damage and repair machinery. DNA repair is particularly important, since this ensures the fidelity of the genetic information to be passed into future daughter cells.
These aren't the only things going on in S phase though. During this time, the cell is also preparing itself for the next mitosis, and various signalling pathways are amplified or attenuated to ensure a smooth transition into mitosis
Mitochondria fuse and elongate to provide the high metabolic demands of genome replication. Centrioles duplicate and elongate, so they can segregate chromosomes without a hitch. And there are many other processes that I may not be aware of.
Basically, there are a number of significantly different processes that occur in G1 phase and S phase, and each and every single one of these processes is important as they serve very specific functions.
17)M PHASE
M phase is the most dramatic period of the cell cycle, involving a major reorganization of virtually all cell components. During mitosis (nuclear division), the chromosomes condense, the nuclear envelope of most cells breaks down, the cytoskeleton reorganizes to form the mitotic spindle, and the chromosomes move to opposite poles. Chromosome segregation is then usually followed by cell division (cytokinesis). Although many of these events have been discussed in previous chapters with respect to the structure and function of the nucleus and cytoskeleton, they are reviewed here in the context of a coordinated view of M phase and the action of MPF.
Q 20.Cell Plate Definition
The cell plate is a structure that forms in the cells of land plants while they are undergoing cell division.
The cells of land plants, unlike animal cells, have a cell wall made of stiff sugars which surround their cell membranes. In addition to protecting the cell from damage, the cell walls help to maintain the plant’s rigid upright structures, such as leaves and stems.
These rigid support structures allow plants to grow tall and spread their leaves wide, obtaining more sunlight. In most plants, the cell wall is made of cellulose – an arrangement of glucose molecules that forms hard, rigid surfaces.
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