Cell Biology:Protein Synthesis

Lesson 2 – Mutations(Inquiry into Life pg. 500-501)

Today’s Objectives Explain how mutations in DNA affect

protein synthesis, including: Give examples of two environmental

mutagens that can cause mutations in humans

Use examples to explain how mutations in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders

Mutations A mutation can be considered a biological

error that produces a change in the organism in some way

Mutations may have no effect, may be harmful, may be fatal, or may even be beneficial

Naturally occurring mutations are a key idea in the Theory of Evolution

Types of Mutations Chromosomal Mutations

Affect a chromosome and therefore many genes

Example: Down’s syndrome Gene Mutations

Affect a single gene Examples: Hemophilia, sickle cell anemia

Types of Mutations Germinal Mutations

An inherited change or mutation of a sex cell (egg or sperm) so all body cells inherit that defective DNA

Germinal mutations can be chromosomal or gene mutations

Somatic Mutation A mutation after development is underway Only some cells are affected Example: birth marks, cancer

Causes of Mutation Can arise spontaneously (due to an

unknown cause) or may be caused by an environmental factor

A factor that increases the chance of mutation is called a mutagen

Environmental Mutagens 1) Chemical – food additives

Hallucinogenic drugs (LSD) Pesticides/fertilizers Industrial chemicals

2) Radiation Non-visible short wavelengths

from electromagnetic spectrum The greater the exposure the

greater the risk

Environmental Mutagens Suspected mutagens are tested on bacteria

and other organisms such as fruit flies, and then mammals (rats, mice)

If mutations (such as cancer) develop, the government restricts its use

Mutagens that lead to an increased chance of cancer are called carcinogens

Types of Defects Gene mutations – affect single genes

Result from 1 or more nucleotide changes Example: Normal strand CAT/ATT/TAG Addition: CAA/TAT/TTA/G

Added an extra A Deletion: CTA/TTT/AG

Lost the first A Substitution: CAT/TAT/TAG

The A and T switched

Examples of Mutations Down Syndrome

A chromosomal translocation Part of chromosome #21 becomes attached to another

chromosome (#12, 14, 14, or 22) Also have 2 normal chromosome #21

Sickle Cell Anemia Substitution of a base to produce a different amino acid Results in abnormal hemoglobin molecules Prevalent in African Americans (10% carry the trait) Causes decreased ability for blood to carry oxygen 2 chromosomes: 1 normal/1 sickle, actually protects

against malaria If both chromosomes are sickle, the condition is fatal

Sickle cell anemia….

Examples of Mutations Cancer

A somatic mutation – affects an individuals body cells

Results in uncontrolled growth of abnormal body cells that fail to stay in the organ where they arose

Hemophilia A germinal mutation (a mutation of the original

sex cells) Passed on to the individual from a previous

generation Impair the body’s ability to control blood

clotting Known as the “royal disease”

Homework Finish the handout given to you last class Next day we will have an assignment due in

class Next week (probably Tuesday) we will have a

DNA replication/Protein Synthesis test