Mitosis and DNA Replication

DNA helicase

A protein that unwinds DNA and breaks the hydrogen bonds between the two strands.

DNA ligase

An enzyme involved in sealing gaps in the sugar-phosphate backbone of DNA by catalyzing the formation of a phosphodiester bond.

DNA polymerase

An enzyme that adds corresponding DNA nucleotides.

replication fork

During DNA replication, the region where the double helix becomes separated by DNA helicase

semi-conservative model

The model of DNA replication where each of the two daughter DNA molecules contains one old strand of DNA and one newly synthesized strand of DNA.

single-strand DNA-binding (SSB) proteins

A stabilizing protein involved in DNA replication that prevents the separated DNA strands from re-joining or re-coiling during the replication process.

Phases of cell cycle

Mitosis is conventionally divided into five phases:

• Prophase

• Prometaphase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis is well underway by late telophase

Interphase (about 90% of the cell cycle) can be divided into subphases:

• G1 phase ('first gap')

• S phase ('synthesis')

• G2 phase ('second gap')

• The cell grows during all three phases

M Phase

also known as Mitosis

Interphase stages: G1

• Creating enzymes for DNA Replication

• cellular content duplicates (organelles etc), chromosomes do not duplicate

Interphase stages: S

• DNA replication

• chromosome duplication (23 pairs)

Interphase stages: G2

• cell creates microtubles

• rapid cell growth

• prepares for mitosis

Prophase

• DNA condenses to form chromosomes

• microtubules move to opposite sides

• nuclear envelop dissolves

Metaphase

• chromosomes line up in middle (metaphase plate)

• kinetochores of sister chromatids attach to kinetochore microtubules from opposite poles

Anaphase

• the two sister chromatids of each chromosome pair move apart to opposite ends of the cell

Telophase

• two daughter nuclei form in cell

• nuclear envelopes reform

• chromosomes less condensed

• one nucleus becomes two (mitosis complete)

Cytokinesis

• formation of cleavage furrow

• cell divides and separates in two daughter cells

malignant tumor

An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor

benign tumor

An abnormal mass of cells that remains at its original site in the body.

cancer

A disease in which some body cells grow and divide uncontrollably, damaging the parts of the body around them

diploid cell (2n)

A cell that has two sets of chromosomes.

Interphase (pic)

Prophase (pic)

Metaphase (pic)

Anaphase (pic)

Telophase (pic)