Biology - Cell Cycle

What are Homologous Chromosomes?

A pair of chromosomes, one maternal, one paternal of similar size and shape with the centromere in the same place. Contain the same genes in the same loci but may contain different alleles.

What happens in growth phase 1?

The cell grows. Increase in the number of organelles. Proteins are synthesised. ATP is synthesised.

What happens in synthesis?

DNA synthesis (semi-conservative replication)

What is the difference between growth phase 1 and 2?

No organelles are synthesised in growth phase 2 whereas they are in growth phase 1.

What are the 4 phases of mitosis?

Prophase. Metaphase. Anaphase. Telophase.

What happens in prophase?

Replicated chromosome with shorten and thicken (supercoil). Nuclear envelope breaks down. Centrioles divide in two and move to each end of the cell to form spindle fibres.

What happens in metaphase?

Each chromosome is attached to a spindle fibre by its centromere. The spindle fibres move them to line up down the equator of the cell.

What happens in anaphase?

Spindle fibres shorten and pull identical sister chromatids to different poles of the cell as the centromeres divide.

What happens in telophase?

Two new nuclei are formed. Spindle fibres break down. Chromosomes uncoil and are no longer visible in a light microscope.

What happens in cytokinesis in animals?

Microtubules form a “draw string” effect which pinches the membrane forming a cleavage furrow. The cytoplasm splits and to identical daughter calls are formed.

What happens in cytokinesis in plants?

Microtubules direct vesicles to the middle of the cell to form a cell plate which becomes a new cell wall as new plasma membrane forms.

How many chromosomes does a diploid cell have?

46 chromosomes.