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Mutations. Defined : one nucleotide is substituted for another May be repaired by DNA polymerase May lead to amino acid change See animation May not lead to any change Ex: DNA “CCC” is mutated into “CC G ” Same amino acid is created (glycine). Gene: Point Mutations. T. A. C. A. G. T.
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Defined: one nucleotide is substituted for another May be repaired by DNA polymerase May lead to amino acid change See animation May not lead to any change Ex: DNA “CCC” is mutated into “CCG” Same amino acid is created (glycine) Gene: Point Mutations T A C A G T G G T C A A A DNA U G U C A C A C A G U U U mRNA cysteine glutamine histidine glutamine phenylalanine Amino acids
Gene: Frame Shift Mutation C A C A G T G G T C A A A DNA • Defined: insertion/deletion of a nucleotide • Entire sequence of DNA/RNA after the mutation is shifted (see animation) • Much more serious to the structure/function of the final protein • mRNA sequence may have early or late “stop codons” G U G U C A C C A G U U U mRNA cysteine histidine glutamine phenylalanine Amino acids histidine serine leucine
Chromosome Mutations • Translocation: Chromosome segments combine with nonhomologous chromosome • Many genes wind up on entirely different chromosomes • Gene cut apart • ½ on chr #5, ½ on chr #8
Down’s Syndrome
Impact on Offspring • Somatic cell mutations • Affect only the individual • Not passed on to future generations • Ex: Muscle cell mutation • Germ cell mutations • May be passed to future generations • Ex: Sperm cell mutation
Mutation Causes • Mutagen: agents in the environment that can change DNA • Speed up replication process • Break apart nucleotides • Ex: UV sunlight breaks hydrogen bond between thymine (T) and adenine (A)