the cell cycle of an animal cell refers to the different stages of the life cycle of that cell now for an animal cell there are two main stages we have the interphase and the M stage also known as mitosis now mitosis is the process by which the cell actually divides into two identical cells and we're going to focus on that stage in the next lecture in this lecture we're going to discuss the process of the interphase or the stage known as interphase now interphase is the stage of the life cycle of the animal cell that prepares the cell for the process of cell division interface is the longest stage of the life cycle of that cell and it takes up about 90% of the time now the reason it's so long is because interphase actually consists of three individual phases we have the G1 phase the S phase as well as the G2 phase now each one of these phases basically serves its own unique function so let's actually discuss each one of these individual phases that together make up our interphase so let's begin with the G1 phase so as soon as the cell divides the cell enters the G1 phase and the G1 phase is known as the the growth phase so basically in this phase our chromosome unwinds and uncoils into UK chromatin and the UK chromatin is used to produce um RNA that is used to synthesize the proteins that are needed by the cell and those proteins are used to synthesize the many organel and the different types of cell Machinery that are needed for the cell's survival so the G one phase is the phasee where we produce the majority of the organel and the proteins that are used by the cell and as a result the cell basically increases in size in fact the cell doubles in size during the phase known as the G1 phase now towards the end of the G1 phase is a checkpoint known as the Restriction point and if the conditions are favorable and if the requirements have been met by the by the cell the cell can basically commit itself to the process of cell division by exiting the G1 phase and entering the next phase of interphase known as the S phase however what happens if the cell doesn't actually want to divide what happens if the conditions are not favorable or if the requirements have not been met in this case the cell exits the G1 phase and it exits interphase entirely and it enters a completely different phase known as the G not phase which is the resting phase of the cell cycle now some some cells spend very little time in the resting phase in the G not phase because they need to continually divide and some examples include skin cells intestinal cells as well well as stomach cells on the other hand other other cells that spend their entire lifetime in the Gen not phase basically that means that our cells do not actually divide and one example of a cell that doesn't actually divide and SP and spends the majority of its time and the g not phase in the wrestling phase is the Nerf cell now if the cell actually want wants to Divine if the cell if the conditions have been met and if the conditions uh and if the requirements have been met if the conditions are favorable then the G1 phase goes into the S phase so if the G1 phase is the growth phase of our cell cycle then the S phase is basically the replication phase in this phase the cell also produces a small amount of proteins and organel but the majority of the resources of the cell basically focus on DNA replication now in human cells all 46 individual chromosomes are actually replicated and the original chromosome and the replicated chromosome are joined together in a region known as the centromere which involves different types of proteins that assist in the joining process so let's take a look at the following grow uh at the following diagram so at the beginning of S phase we have individual original chromosomes but as the S phase proceeds we basically use the cell Machinery to replicate our DNA molecule the chromosomes so each one of the 46 individual chromosomes in human cells are replicated and we produce the following two chromosomes the original as well as the replicated and we joined these two uh chromosomes by using special proteins at a region known as the centromere found in this censor location now once we actually replicate the individual chromosomes these individual chromosomes are now known as chromat chromatids so at this point the cell basically contains 46 original chromatids and 46 replicated chromatids to make a combined total of 92 chromatids so at the end of S phase our cell contains 92 chromatids in human cells now once the S phase is is completed it goes on into the G2 phase so the G2 phase is basically the phase of interphase that make sure that the cell is fully prepared for the process of mitosis for the process of cell division so in this phase our cell basically continues producing the proteins and the organel that are needed by that cell so once the chromosomes are replicated and the chromosome number is doubled the cell enters the G2 phase during this phase the cell prepares for cell division by making sure it contains enough proteins and organel that means protein syn synthis and organel production continues in the G2 phase now at the end of the G2 phase just like the G1 phase contains a checkpoint the G2 phase also contains a checkpoint at the end at the checkpoint the cell basically checks for the level or the concentration of a certain type of protein known as the mitosis promoting factor or mpf mpf sometimes s also stands for the maturation promoting Factor now if the concentration levels are high enough the cell will basically exit the G2 phase and exits the interphase and enters the second stage known as the M stage so as we'll see in the next lecture this is the stage that consists of the process of mitosis which is the process by which the cell basically divides and produces an identical daughter cell now mitosis can be broken down into prophase metaphase anaphase and telophase and the process by which the cell actually divides is known as cyto Kinesis and we'll discuss that in the next lecture so basically the process of interphase is the first stage of the life cycle of an animal cell interface consists of the G1 phase the S phase and the G2 phase in the G1 phase the cell basically grows in size because the majority of the proteins and and organel are synthesized within our cell the S phase is basically the replication phase this is when the cell actually replicates the DNA now the last phase the G2 phase this is the phase in which the cell basically makes makes sure that the cell is prepared for the process of cell division so the cell continues to synthesize the proteins as well as our organ naels