Genetic Information is Copied and Passed on to Daughter Cells

Genetic Information and Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its nucleus into two identical sets, each in its own new nucleus.
It ensures accurate duplication of the chromosomes and allows for genetic consistency across cells.
Prior to mitosis, DNA in the cell undergoes replication during the S phase of interphase.

DNA Replication

The DNA molecule ‘unzips’, breaking the hydrogen bonds between base pairs, creating two strands which act as templates for new DNA.
DNA polymerase catalyses the addition of complementary nucleotides, according to base pairing rules: A with T and C with G.
The end product of replication is two identical DNA molecules, each with one old strand and one newly synthesised strand. This is known as semi-conservative replication.

Cell Cycle Checkpoints

Checkpoints in the cell cycle ensure proper DNA replication and correct any errors to maintain genetic stability.
Important checkpoints are located at the G1/S transition, the S phase, and the G2/M transition.
At the G1/S transition, the cell checks for DNA damage that may have occurred during the cell’s resting phase, known as G0.
During the S phase, the cell checks for improper DNA replication or DNA damage.
The G2/M transition checkpoint ensures all chromosomes have been properly replicated and repaired before the cell enters mitosis.

Mitosis and Cytokinesis

Mitosis is divided into four stages: prophase, metaphase, anaphase and telophase.
During prophase, the nuclear envelope breaks down and the chromosomes condense.
Metaphase sees chromosomes align along the cell’s equator.
Anaphase involves the separation of sister chromatids, while during telophase a new nuclear envelope forms around each set of chromosomes.
Mitosis is followed by cytokinesis, where the cell splits into two daughter cells, each with a complete set of the parent cell’s DNA.

Genetic Consistency and Variation

The process of mitosis helps preserve the genetic identity of cells, ensuring each daughter cell is genetically identical to the parent cell.
Errors, or mutations, can occur during DNA replication. These may have no influence, or they can affect cell function and cause disease.
While these mutations can lead to problems, they can also lead to genetic variation, which is essential for evolution.