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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 - PowerPoint PPT Presentation
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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