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BIO 2400 (24)
Lecture 16

BIO 2400 Lecture 16: Ch. 16

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BIO 2400
Annkatrin Rose

Ch. 16 • What are Genetic Mutations? o Heritable changes in the genetic material (change in DNA sequence) o Lead to genetic & phenotypic variation • Germ Line/Somatic Cells o Germ Line mutations occur in a sperm or egg cell (or one of their precursor cells) ▪ Inherited by the offspring ▪ Ex. Genetic disorders o Somatic mutations occur in a body cell (or one of its precursor cells) ▪ Not inherited by the offspring ▪ Ex. Cancer • Mutations provide new alleles o Gene mutations provide allelic variations ▪ Phenotypic variation • Foundation for evolutionary change • More likely to be harmful than beneficial • Often the cause of disorders o Types of MUTATIONS: ▪ Wild-type • Prevalent allele in a population o Some genes with multiple alleles may have two or more wild types ▪ Forward mutation • Changes the wild-type genotype into some new variation ▪ Reverse mutation (reversion) • Changes a mutant allele back to the wild-type  VARIANTS alter an organism’s phenotypic characteristic ▪ Deleterious mutations • Decrease the chances of survival (could be lethal mutations) ▪ Beneficial mutations • Enhance the survival or reproductive success of an organism ▪ Conditional mutations • Affect the phenotype only under a defined set of conditions o Ex. Temperature sensitive mutation ▪ Point mutation • Change in a single base pair o Transition= change of a (C,T) to another (C,T) ▪ ^^^^MORE COMMON o Transversion= change of a (C,T) to a (A,G) or vice versa • Addition and Deletion ▪ Silent Mutations • Base substitutions that do not change the amino acid sequence ▪ Missense mutation • Base substitutions that change one amino acid ▪ Nonsense mutation • Base substitutions that change a normal codon to a terminal codon ▪ Frame shift mutation • Addition/deletion of nucleotides in multiples of one or two • Spontaneous Mutations o Cellular/biological processes gone wrong o Ex. Errors in DNA replication • Induced Mutations o Caused by environmental agents (mutagens) that alter DNA structure o Can be chemical or physical agents o Ex. X-rays o Of public concern for 2 main reason: ▪ Often involved in development of cancer ▪ Can cause gene mutations with harmful effects in future generations • Mutagens Alter DNA Structure in Different Ways o 3 main types of chemical mutagens • 1.Base modi
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