What happens to a cell before it enters mitosis?

Before mitosis, the cell goes through a phase called interphase. However, interphase is subdivided further into three other phases, and knowing what happens during each of them is crucial for us if we want to understand mitosis and meiosis.As menitioned above, interphase is divided into three phases: G1 (gap one) phase, S (synthesis) phase and G2 (gap two) phase. Let's look more closely what exactly happens in the cell during all these phases:

G1: During G1 phase, all the organelles in the cell replicate, except the genetic material (DNA)

S: During the S phase, the DNA is replicated. The process od DNA replication is a highly complex process, so I will not describe it more specifficaly in this post. All you need to know about the S phase is that the DNA replicates. NOTE! The DNA in our cells is packaged up into chromosomes. Here is how the chromosomes look like after the synthesis phase (after the DNA replication):

G2: During the G2 phase, the cell continues to grow. All the enzymes needed for mitosis are produced during G2 phase

During interphase, the cell goes through various checkpoints which controll that all the phases have been successfully completed. If there is an error (for example, if the DNA has been copied incorrectly), the cell will not divde.
I have also made a video about this topic. Please, check it out here: My video about interphase

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