BIO 101 Ch8 DNA Replication Binary Fission Mitosis

Why must DNA be replicated?

Before a cell divides, its whole genome must be copied so each daughter cell gets a complete set.

What does semiconservative replication mean?

Each new DNA molecule has one old strand and one newly made strand.

What does helicase do?

Unwinds and separates the two DNA strands at the replication fork.

What does DNA polymerase do?

Adds new nucleotides to build the new strand, always in the 5 prime to 3 prime direction, and proofreads for errors.

What is primase for?

Makes a short RNA primer that gives DNA polymerase a starting point.

Leading vs lagging strand?

Leading strand is built continuously toward the fork. Lagging strand is built away from the fork in short pieces.

What are Okazaki fragments?

Short DNA segments made on the lagging strand, later joined together.

What does DNA ligase do?

Seals the gaps and joins Okazaki fragments into one continuous strand.

Base pairing rules in DNA?

A pairs with T and G pairs with C.

What is binary fission?

How prokaryotes divide: copy the circular chromosome, grow, and split into two identical cells. Simpler than mitosis.

What is mitosis for?

Growth and repair. It produces two genetically identical daughter cells.

Order of the mitosis phases?

Prophase, metaphase, anaphase, telophase (then cytokinesis). Memory trick: PMAT.

What happens in prophase?

Chromosomes condense, the nuclear envelope breaks down and spindle fibers form.

What happens in metaphase?

Chromosomes line up along the middle (the metaphase plate).

What happens in anaphase?

Sister chromatids are pulled apart toward opposite poles.

What happens in telophase and cytokinesis?

Nuclei re-form around each set of chromosomes and the cytoplasm splits into two cells.

What is the cell cycle?

Interphase (G1, S where DNA is copied, G2) followed by mitosis and cytokinesis.

What do checkpoints do?

Catch chromosome errors during division and stop the cycle until they are fixed. Mistakes still happen occasionally.

How does cancer relate to cell division?

Cancer is cells losing normal limits on division and ignoring stop and repair signals.

What is the hardest concept per Dr. Hinn?

DNA replication. Read that section 2 to 3 times before lecture.