Cell Cycle and Chromosomes

It is the first stage of mitosis, during which the chromosomes condense and become visible. The nuclear membrane breaks down & the chromosomes condense during prophase.

Double minute chromatin bodies are indicative of gene amplification, one of the mechanisms of oncogene activation.

Cells in blood, hair, finger nails, and any other tissues in our body can be cultured to create a karyotype of the chromosomes. Since all of your somatic cells will have the same chromosomes, it generally doesn't matter which ones are used.

Because sex chromosome abnormalities rarely result in an early death and their symptoms are not often severe, comparatively large number of people with these abnormalities survive to old age.

Each generation of offspring bears so many possible impregnation of maternal and paternal traits as a consequence of the frequent grabbing of chromosomes by the microtubules during metaphase I.

Phagocytes literally means eating of the cells. To do this, and be able to get the nutrients from inside the cell, it has to break down the outer defenses (cell walls, cell membranes, plasma membranes). The cytoskeleton provides the structural integrity for the cell, so it should be disassembled.

In the process of meiosis, four haploid daughter cells are formed. In humans, cells that go through meiosis are the sperms and egg cells. The reason why DNA does not duplicate between meiosis I and meiosis II is because only half the number of chromosomes is necessary in a sperm or egg cell. That's why, when a sperm fertilizes an egg, each cell has half the number of chromosomes necessary to create an organism, so together, they have the correct amount of chromosomes.

It is described as a phase where the chromosomes at each pole uncoil and enlarges to form chromatin. Nucleolus and nuclear membrane are re- formed surrounding each chromatin network. Asters and spindle fibres disappear and centrioles divide. Daughter nuclei are formed.

This is described as the process when a segment of chromosome splits and relocates within a non- homologous chromosome.

This type of sex determination occurs in insects and mammals including human beings. Here, the females bear two identical homologous sex chromosomes designated as XX and the males bear two dissimilar sex chromosomes designated as X and Y. Thus, females are homogametic, producing only one type of ovum, and males are heterogametic, producing two types of gametes.

Here the centromere is located far away from the centre of the chromosome so that the two arms are highly unequal. The chromosome acquires the shape of 'J' during anaphase.

It leads to the new genetic combinations as a result of crossing over. This situation brings about variations.

 It is described as the stage where each chromosome breaks into two chromatids forming four chromatids; two paternal and two maternal which are known as tetrads. Chiasma is the site of an exchange of genetic material between the two chromatids. It occurs due to breakage and reunion between the two non-sister chromatids. This process is called genetic recombination.

It is described as the phase where chromosomes become short & visible as single structure. It contains the dense stained chromomeres.

Here DNA replication takes place. Protein molecules namely histones are synthesised and cover each DNA strand.