Mitosis and the cell cycle

What are the 2 main stages in the cell cycle?

Mitosis and interphase

How many phase are in interphase?

3

What are the three phase in interphase?

G1, S and G2

What is the G1 phase?

The cell is preparing to replicate DNA by synthesising the mRNAs and proteins required to execute future steps. The cell usually grows larger and some organelles are copied

What is the S phase?

All of the genetic information is copied by the process of DNA replication, this generates sister chromatids which are identical pairs of chromosomes, they are attached by a centromere (specialised sequence of DNA)

What is the G2 phase?

During this the cell undergoes additional growth, replenishes energy stores, prepares and reorganises the cytoplasmic components. It ends when mitosis begins

What is mitosis?

A series of processes during which the replicated DNA condenses into visible chromosomes, which are aligned, separated, and passed onto two new daughter cells

What are the 5 stages of mitosis?

Prophase, pro-metaphase, metaphase, anaphase and telophase

What is prophase?

During prophase the chromosomes start to condense, the nuclear envelope breaks down and organelles break up and move towards the outside of the cell. Mitotic spindles also begin to form at opposite poles of the cell. They are made out of microtubules and are important for moving chromosomes

What is pro-metaphase? (don’t need to know)

In this stage the nuclear envelope is broken down and the chromosomes are fully condensed. The mitotic spindles begin to organise the chromosomes. A structure called the kinetochore also appears, the kinetochore is a protein structure important for linking the chromosomes and spindles. It is assembled on the centromere

What is metaphase?

The mitotic spindles move the chromosomes so that they align in the middle of the cell, the metaphase plate. At this point the sister chromatids are still attached to one another. Following metaphase there is an important checkpoint called the spindle checkpoint. This ensures that anaphase will not proceed unless all the chromosomes are at the metaphase plate.

What is anaphase?

When the chromosomes are properly aligned, anaphase can proceed. During anaphase the sister chromatids separate at the centromere and are pulled to the edge of the cell. These chromatids are now referred to as chromosomes

What is telophase?

During telophase the spindles disappear and a new nuclear envelope forms around the chromosomes. The chromosomes start to decondense as cytokinesis takes place