Download Chapter 2: How Chromosomes Work

How Chromosomes Work
The Chromosome Theory
1. chromosomes—long strands of DNA found in the nucleus of every cell
2. a. Walther Flemming—discovered chromosomes while studying salamanders;
he had physical evidence that chromosomes existed (you could see them
with a microscope)
b. Walter Sutton—discovered where genes were located while studying
grasshoppers---he had theoretical evidence to support his idea—you
couldn’t actually see the genes on the chromosomes; he also recognized
that sex cells contain half the number of
chromosomes as regular body
cells
3. The Chromosome Theory—genes are carried from parent to offspring on
chromosomes
4. genes, chromosomes, and proteins—The main function of genes on
chromosomes is to control the production of proteins. Proteins determine the
characteristics (or traits) of an organism.
5. meiosis—process of cell division that creates sex cells
6. steps of meiosis—
a. chromosomes double
b. cell divides
c. cell divides again
7. sex chromosomes/Thomas Hunt Morgan—Morgan discovered sex
chromosomes while studying fruit flies. He noticed one pair of chromosomes that
was shaped differently. This was the male sex chromosomes. The female gets
two rod shaped X chromosomes. The male get one rod shaped X chromosome
and one small hook shaped Y chromosome.
Female = XX
Male = XY
2-2: Mutations
8. mutations/Hugo DeVries—Hugo DeVries accidentally discovered mutations
while studying American Primroses.
9. non-sex cell vs. sex cell mutations—a non-sex cell mutation only affects the
organism that has the mutation (it cannot be passes on to offspring); a sex cell
mutation is a mutation that can be passed on to offspring
10. harmful mutations—a sudden change in a gene or chromosome that decreases
an organism’s chance for survival
Example: albino deer and sickle cell anemia
11. helpful mutations—a sudden change in a gene or chromosome that increases an
organism’s chance for survival
Example: seedless fruits and vegetables
12. mutation vs. mutagen vs. mutant—
mutation -- the change
mutagen – the cause of the change
mutant – the organism being changed
Example: skin cancer
mutation = skin cancer
mutagen = UV radiation from sun
mutant = person with skin cancer