BB lecture 11-16-09 mutations, operons

BB lecture 11-16-09 mutations, operons - Chapter 17 (pp....

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 17 (pp. 344-346 in conclusion) Learning objectives: • Define mutagen ; mutation; point mutation • Explain why point mutations are sometimes harmful, and sometimes harmless • Be able to illustrate a frameshift mutation Chapter 18 (pp.351-356): Gene regulation Learning objectives: • Define operon • Explain the difference between repressible and inducible operons • Be able to describe how the trp operon and the lac operon respond to different nutrient conditions Mutagen: a natural or man-made agent (chemical or physical) which can alter the structure or sequence of DNA. Chemical mutagens 1. Base analogs – molecules structurally similar to purines and pyrimidines 2. Chemicals - which alter structure and pairing properties of bases 3. Intercalating agents – molecules which may “insert” between bases Physical mutagens Radiation Ionizing radiation (UV, x-rays, gamma rays, etc.) produce free radicals-Free radicals damage DNA, proteins, lipids in cell membranes, etc. • Mutation : a change in a gene’s DNA . • Mutations that cause cancer are typically called “carcinogens ” • A spontaneous mutation occurs as a result of natural processes (example: during DNA replication, recombination, or repair). • Point mutations: changes in a single base pair of a gene • may change an amino acid codon to a termination codon or vice versa..can result in a prematurely shortened protein • may be silent , NOT changing the sequence of amino acids in the protein – often true in the third position of a codon, because of "wobble" base pairing Types of Point Mutations • Point mutations - two general categories 1. Base-pair substitutions 2. Base-pair insertions or deletions Substitutions • A base-pair substitution replaces one nucleotide and its partner with another pair of nucleotides • Base-pair substitution can cause nonsense or missense mutations – Nonsense mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein – Missense mutations still code for an amino acid , but not necessarily the right amino acid- Missense mutations are more common Base-pair...
View Full Document

This note was uploaded on 01/20/2010 for the course BIO 50415 taught by Professor Batterton during the Spring '09 term at University of Texas.

Page1 / 24

BB lecture 11-16-09 mutations, operons - Chapter 17 (pp....

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online