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32
Both unicellular and multicellular organisms undergo mitosis. What are the differences, if any, observed in the process between the two?
Explanation

In unicellular organisms, the type of cell division is known as amitosis in which somatic cell is divided into two parts directly. In multicellular organisms occurs which is an indirect process.

Both cell division in unicellular and multicellular organisms undergo mitosis have differences as below

Cell Division in Unicellular Organism (Amitosis) Cell Division in Multicellular Organism (Mitosis)
It is direct division of cellular and nuclear content. Without the formation of chromosomes. Nucleus and cellular content do not divide directly and involves formation of chromosomes.
Different phases of cell divisions are not seen. It involves different phases of cell division.

33
Name the pathological condition when uncontrolled cell division occurs.
Explanation

Cancer is the pathological condition in which the cells loose control over cell division and this results into malformation of the organ in which such cell division occurs.

34
Two key events take place, during $S$-phase in animal cells, DNA replication and duplication of centriole. In which parts of the cell there events occur?
Explanation
DNA replication takes place in nucleus and duplication of centriole occurs in the cytoplasm. Centriole forms spindle fibres during cell division in animal cells which direct the movement of chromosomes within the cell. The position of centriole determines the position of the nucleus and plays a crucial role in the spatial arrangement of the cell.
35
Comment on the statement-meiosis enables the conservation of specific chromosome number of each species even through the process per se results in reduction of chromosome number.
Explanation
Meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms. Even though the process results in reduction of chromosome number by half, it is gradually conserved by union of male gamete $(n)$ and female gamete $(n)$ in next generation. Meiosis also increases the genetic variability in the population of organisms from one generation to the next.
36
Name a cell that is found arrested in diplotene stage for months and years. Comment in 2-3 lines how it completes cell cycle?
Explanation

Meiotic arrest at diplotene stage commonly occurs in mammalian occytes. In females, meiosis starts in the embryo and proceeds as for as diplotene, when the chromosomes become diffused and the cells are referred to as being in the dictuate stage. This arrest is under hormonal control.

In many amphibian oocytes binds and insects with a long period of immaturity, the oocyte may be arrested in the dictyate stage for many years and spend a prolonged period in diplotene.

This stage is characterised by formation of lampbrush chromosomes where intense RNA synthesis occurs and most of the genes in the DNA loops are actively transcribed and expressed.