Cell Cycle and Chromosomes

Proteins required for formation of spindle are formed in G2 phase by centrioles.

10% of the time is spent in M-phase.

In animal cells, the astral rays emerge out from centrosomes and give centrioles star-like appearance.

The nucleoli and nuclear membrane disappear in prophase of mitosis.

Chromosomes can be identified and counted because each chromosome becomes more compact and short.

Chromosomes start becoming visible under light microscope in prophase.

Metaphase stage is the most suitable phase for counting and identifying chromosomes.

In anaphase, centromeres of each chromosome divide and permit the separation of two chromatids.

During telophase, nuclear membrane reappears, chromatin network is formed and spindle fibres disappear.

During ovulation, the oocyte is arrested in the metaphase of the second meiotic division.

Chronic myelogenous leukemia is an uncommon type of cancer of the blood cells. The t(9;22) describes the Philadelphia chromosome, in which the bcr gene on chromosome 22 is juxtaposed to abl on chromosome 9.

Alpha satellite DNA is a repetitive sequence known to be a major DNA component of centromeres in primates (order Primates).

XX male syndrome is a rare sex chromosomal disorder. Usually it is caused by unequal crossing over between X and Y chromosomes during meiosis in the father, which results in the X chromosome containing the normally-male SRY gene.

Spindle formation starts at prophase.

Cells are the fundamental units of life. The nucleus stores its genetic material in packages called chromosomes. Most people have 46 chromosomes in each cell—23 from their mother and 23 from their father.