Genetic Information is Copied and Passed on to Daughter Cells

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.