Cell Division-Mitosis

Squash Preparation

Chromosomes only become visible during cell division. When cell division is observed, the chromosomes must be stained in order to make them more visible. The stain applied is usually acetic orcein. Tissue is placed on a slide and gently pressed to spread out the chromosomes allowing more light through and therefore giving a greater resolution.

Interphase

Comprises the G1 phase, S phase and the G2 phase. The cell spends most of its time in interphase. events include DNA replication, Organelle replication and ATP production.

Haploid

Contains half the number of chromosome of the parent cell.

Anaphase

The centromere is split and the chromatids are pulled apart towards the two poles. The spindle fibres are known to shorten. Anaphase is over once the separated chromatids arrive at the poles.

Metaphase

The chromosomes arrange themselves on the equator of the spindle. Each chromosome is attached to a separate spindle fibre by the centromere; there is no association of homologous chromosomes in mitosis.

Prophase

The chromosomes condense and become visible as two chromatids joined by a centromere. Centrioles appear at opposite sides of the nucleus and the spindle apparatus starts to form. It consists of a collection of protein microtubules but is not produced by the centrioles. The nucleolus disappears and prophase ends with the breakdown of the nuclear envelope.

Telophase

The condensed chromosomes unravel, a new nuclear envelope forms around each group of daughter chromosomes, the spindle disappears, and a new nucleoli appear.

Centrioles

Appear at opposite sides of the nucleus and the spindle apparatus starts to form during prophase.

Diploid

Full set of chromosomes. Chromosomes are genetically identical to the parent cell and are arranged in 23 pairs.

Condense

In prophase stage of mitosis, the chromosomes start to condense and become visible as two chromatids, joined by a centromere.

Spindle

In prophase, spindle fibres start to form. Spindle fibres consist of a collection of protein microtubules. The spindle fibres appears in prophase and disappears in telophase.

Nucleolus

In prophase, the nucleolus disappears and ends with the breakdown of the nuclear membrane. Nucleolus reappears in telophase.

S-Phase

Synthesis phase of interphase. DNA replication occurs to produce chromatids.

Centromere

Two chromatids are joined by a centromere. In metaphase, each chromosome is attached to a separate spindle fibre by the centromere. In anaphase the centromere is split.

Cytokinesis

Usually starts before telophase is completed and results in cytoplasmic cleavage and the production of the two, separate daughter cells.

Chromatids

When chromosomes condense in prophase, they become visible as two chromatids joined by a centromere. (Clone of parent chromosome)