Ch. 9 (Pt. 2): Mutations

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Department
Biology - Biological Sciences
Course
BSC 2010
Professor
Gerlach, Nicole
Semester
Spring

Description
3/11/13 Ch. 9: Mutations I. Mutations A. Mutations – changes in the nucleotide sequence of DNA that are passed on from one cell or organism to another B. The ultimate source of all genetic variation C. 2 types: 1. Somatic mutations – occur in body cells; passed on by mitosis but not to sexually produced offspring 2. Germ line mutations – occur in cells that give rise to gametes; gamete passes a mutation on at fertilization D. Phenotypic effects: 1. Advantageous: beneficial 2. Deleterious: harmful 3. Neutral: no effect a. Deleterious and neutral effects are more common E. Random errors are unlikely to “improve” by chance on current survival and reproduction of the individual F. Most genomes include genes and regions of DNA that are not expressed 1. Coding: phenotypic consequences 2. Non-coding: none G. Silent mutation – does not affect protein function H. Loss of function mutation – leads to proteins and enzymes that don’t work 1. Almost always recessive I. Gain of function mutation – leads to a protein w/ an altered function II. Point Mutations A. Point mutations – when a single nucleotide changes B. Due to errors in replication or environmental mutagens C. Usually causes changes in mRNA D. Base substitutions – replacement of 1 nucleotide by another in the DNA sequence 1. Synonymous (silent) – does not affect the amino acid sequence 2. Missense mutation – May result in a defective protein, reduced protein efficiency, or a gain of function a. Nonsense mutations - result in substitution that causes a stop codon to form somewhere in the mRNA, resulting in a shortened protein
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