Mitosis And Mutations Flashcards
What is a chromosome
A chromosome is a substance made up of a mass of coiled threads of DNA and proteins
What cycle do cells divide in
They divide in a sequence of events known as the cell cycle which involves several different phases.
What are the different phases in the cell cycle
Interphase (this is where the G1, S and G2 stages come under), mitosis and then cytokinesis
What takes place during the interphase stage of the cell cycle
The interphase period is a period where the cells increase in mass and size, carry out normal cellular activities and replicate their DNA already for division
What takes place during the G1 (Gap 1) stage in the cell cycle
G1 is the time between the end of the previous round of mitotic cell division and the start of chromosome duplication. The cell assimilates material, grows and develops. This is the time that is most variable. It can range from a few hours too years.
What takes place during the S stage
The S stage is when the chromosomes replicate and become double stranded chromatids ready for the next cell division
What takes place during the G2 (Gap 2) stage in the cell cycle
G2 is the time that the organelles and other materials needed for cell division are synthesised. Before a cell can divide it needs two of everything
What takes stage during mitosis in the cell cycle
Mitosis is when the cell divides to produce 2 genetically identical daughter cells
What takes place during cytokinesis in the cell cycle
Cytokinesis is the final stage of the cell division when the new cells separate
How is the cell cycle controlled
The cell cycle is controlled by a number of chemical signals made in response to different genes. This control is brought about at a number of checkpoints where the cell cycle moves from one stage to the next. The control chemicals are small proteins called cyclins. These build up and attach to enzymes called cyclin-dependent kinases (CDK’s). The CDK complex formed phosphorylates other proteins, changing their shape and bringing about the next stage in the cell cycle
What are the different stages of mitosis
Interphase, Prophase, metaphase, anaphase, telophase and then cytokinesis
What organelles are replicated during interphase
During interphase new DNA is produced as the chromosomes replicate. New proteins, cytoplasm and cell organelles are also synthesised so that the cell is ready for the production of 2 new cells. Interphase finishes when the parent cell is large enough
What takes place during prophase
By the beginning of prophase both the original and copies of chromosomes are referred to as chromatids. In prophase the chromosomes coil up, can take up stains and become visible. Each chromosome at this point consists of 2 sister chromatids that are attached to each other in a region known as the centromere. The centrioles begin to pull apart to form the spindle and the nucleolus breaks down.
What takes place during metaphase
The nuclear membrane has broken down and the centrioles have moved to opposite poles of the cell forming a set of microtubules between them that is known as the spindle. The chromatids line up on the equator of the spindle during metaphase with each centromere associated with a microtubule of the spindle
What takes place during the anaphase stage
The centromeres that have linked the 2 identical chromatids split and from then on the chromatids act as completely separate entities. They effectively become new chromosomes. The chromatids from each pair are drawn towards opposite poles of the cell. At the end of anaphase the two sets of chromatids have been separated to opposite ends of the cell. The chromatids rely on the microtubules of the spindle to allow them to move.
