BIOL 211 - CELLULAR AND ORGANISMAL BIOLOGY

Lecture Outline for February 23, 2005

Topics: control of the cell cycle

Chapter 8 section 8.2, a little from 8.3

Figures used in lecture: 8.2, 8.7, 8.10, 8.12

Additional resources

Cell Cycle - discusses cell cycle control, checkpoints, cyclins, kinases (more detail than we will cover)

Ontact Inhibition - cancer cells in culture

Key Words

Cell cycle control, checkpoints, cyclins, kinases, contact inhibition

Fig. 8.2

Mitosis: nuclear division

stages:

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Prophase

nuclear envelope dissolves

chromosomes condense

kinetochores form at the centromere of each chromosome

microtubules of the spindle attach to each kinetochore

Metaphase

microtubules pull kinetochores

chromosomes are aligned on the equatorial plate (metaphase plate)

at the end, centromeres divide in 2

Anaphase

daughter chromosomes are pulled to opposite poles of the cell

microtubules shorten causing the chromosomes to be pulled apart

Telophase

chromosomes decondense (uncoil)

spindle is broken down

a new nuclear envelope forms around each daughter nucleus

Cytokinesis: cytoplasmic division

animal cells – cleavage furrow

plant cells - form a cell plate

Cell Cycle Control

Checkpoints

times during the cell cycle when specific proteins interact to start/stop the cycle

Control can be done by

a) Extracellular signals

b) Intracellular signals

cyclins –

kinases –

Contact inhibition:

Cancer cells

uncontrollable cell growth forms a tumor

have lost contact inhibition

Meiosis

Sexual reproduction: combining of genetic information (genes) from 2 parents to form offspring

Q. How many chromosomes do humans have?

Homologous pairs of chromosomes:

Homologous pairs contain the same genes (traits) but they are NOT IDENTICAL

Gene:

Allele:

Diploid:

Haploid:

Q. If each parent has 23 pairs of chromosomes, how do they produce offspring with only 23 pairs?