Cell Cycle & Mitosis Test - 1

• Karyokinesis is the division of the nucleus and is followed by Cytokinesis, the division of the cell cytoplasm.
• An epithelium or tissue characterized by cytoplasmic continuity or a large mass of cytoplasm not separated into individual cells and containing many nuclei. 
• In coconut, repeated free-nuclear divisions take place. If a cell wall is formed it will form after free-nuclear divisions. This process is known as Nuclear endosperm formation.

First statement, Mitosis takes place in the somatic cells and meiosis takes place in the germ cells, is true.

The G₀ phase or “resting phase” is a period in the cell cycle in which cells exist in a quiescent state. Differentiated cell remains at this G₀ stage.

In animal cells, during synthesis or S-phase, DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm. During this time, the amount of DNA per cell doubles. However, there is no increase in the chromosome number.

• Polyploidy, the condition in which a normally diploid cell or organism acquires one or more additional sets of chromosomes.
• In other words, the polyploid cell or organism has three or more times the haploid chromosome number.
• Polyploidy arises as the result of total nondisjunction of chromosomes during mitosis or meiosis.
• Cells are polyploid if they contain more than two haploids (n) sets of chromosomes; that is, their chromosome number is some multiple of n greater than the 2n content of diploid cells. For example, triploid (3n) and tetraploid cell (4n) cells are polyploid.

• The spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division i.e., mitosis and meiosis.
• At the beginning of nuclear division, two wheel-shaped protein structures called centrioles position themselves at opposite ends of the cell forming cell poles.
• Long protein fibres called microtubules extend from the centrioles in all possible directions, forming what is called a spindle. 
• Some of the microtubules attach the poles to the chromosomes by connecting to protein complexes called kinetochores.
• Kinetochores are protein formations that develop on each chromosome around the centromere, which is a region located near the middle of a chromosome.
• During the cell division phase called metaphase, the microtubules pull the chromosomes back and forth until they align in a plane along the equator of the cell, which is called the equatorial plane.
• During anaphase, the chromosomes are simultaneously separated and pulled by the spindle to opposite poles of the cell.

The process where a single cell divided resulting in generally two identical cells, each containing the same number of chromosomes and genetic content as that of the original cell. It takes place in cancer cell.

Spindle fibres are created at the opposite poles of the cells during the prophase stage of mitosis. They are made up of microtubules. These clusters of microtubules are responsible for moving chromosomes during cell division. They contain 3% RNA and 97% tubulin.