Lecture #1 (The Cell Life Cycle)

Why is cell division important?

It is how:
• 1 fertilized cell becomes 40 trillion cells at maturity
• New cells are added to growing structures
• Old/damaged cells get replaced

What two things are required for cell division to successfully occur?

1. DNA replication
2. Mitosis

Define Cell Cycle

series of changes a cell goes through from the time it is formed to the time it
reproduces itself

What are the 2 major phases of the cell cycle?

1. Interphase
2. Mitosis/Mitotic phase

What is the major event that occurs in a cell during the G1 subphase of interphase?

Lots of cell growth

During the S phase - what major event occurs to the chromosomes?

DNA replication occurs creating sister chromatids attached together

What structure holds the sister chromatids together?

A centromere (protein)

Describe what occurs during the G2 subphase of interphase

enzymes and other proteins needed for
division are synthesized

Final preparation for mitosis

What happens to the centrosome by the end of interphase?

The centrosome completes replication. Now there
are 2 centrosomes instead of 1

During prophase - what happens to the nuclear membrane/envelope and the sister chromatids (chromosomes)?

The nuclear membrane/envelope breaks down

The sister chromatids (chromosomes) condense, making them easier to move around the cell

What does the pair of centrosomes build during prophase?

A network of protein rods (microtubules) known as the Mitotic Spindle Apparatus

Describe the unique arrangement of chromosomes that occurs during metaphase and how the sister chromatids (chromosomes) get there

The mitotic spindle apparatus attaches to the centromere of each sister chromatid, then move the sister chromatids and lines them up on the metaphase plate.

What occurs to the sister chromatids (chromosomes) during anaphase? How does this happen?

- One chromosome from each pair moves to opposite sides of the cell

- The mitotic spindle apparatus separates each pair of sister chromatids

During telophase - what happens to the nuclear membrane/envelope and the chromosomes?

The nuclear membrane/envelope reforms, and the chromosomes decondense

What happens to the mitotic spindle apparatus during telophase?

The mitotic spindle apparatus breaks down but the centrosome remains

What is cytokinesis?

When the cytoplasm splits creating two separate daughter cells

What must the cell "pass" before progressing into the S subphase of interphase?

A restriction point