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 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
 gene mutation
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gene mutation

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  • 1.  Discuss the difference betweenadaptation to environmental mutationsand heritable changes due to mutations List several different types of mutationsand discuss how mutations arise in cells
  • 2.  The genetic material can be changedthrough mutations, which are changes inthe nucleotide sequences of genes Changes that are not repaired are calledmutations Early in this century, some geneticistssupported the theory that environmentalconditions could cause all heritablechanges in the genetic material(adaptations)
  • 3.  A mutation is a change in a DNA base-pair or region of chromosome, of whichthere are many causes A somatic mutation affects the individualin which it happens and is not passed onto the succeeding generation Germ-line mutations may be transmittedby the gametes to the next generation,producing an individual with mutations inboth the somatic and germ-line cells Germ-line mutations are heritable
  • 4.  A chromosomal mutation or aberration isa change in the structure or number ofchromosomes A gene mutation is a change in the DNAsequence of a particular gene Mutations can occur spontaneously or beinduced by a mutagen, which is achemical or physical agent that increasesthe frequency of mutational events
  • 5.  Spontaneous mutations occur naturally A point-mutation is a base-pair substitutionmutation, in which one base pair isreplaced by another base pair (AT to GC)
  • 6.  Point mutations include: Transition mutations, in which the change isfrom one purine-pyrimidine base pair tothe other purine-pyrimidine base pair (ATto GC, GC to AT, TA to CG, and CG to TA) Transitions can be caused byoxidative deamination.
  • 7.  Transversion mutations involve a changefrom a purine-pyrimidine base pair to apyrimidine-purine base pair (AT to TA,GC to CG, AT to CG, and GC to TA) the consequences of this change tendto be more severe than those oftransitions. Transversions can be caused byionizing radiation.
  • 8.  Mutations can be defined according totheir effects on amino acid sequences inproteins and include: Missense mutations, a gene mutation inwhich a change in the DNA causes achange in an mRNA codon so that adifferent amino acid is inserted into apolypeptide during biosynthesis
  • 9.  In sickle-cell anemia: a single nucleotidebase-pair change in codon 6 of the β-hemoglobin gene leads to an amino acidsubstitution in the β-hemoglobin chain Nonsense mutations, in which an mRNAcodon is changed from an amino acid intoa stop codon (UAG, UAA, or UGA)
  • 10. A Nonsense Mutation and its Effect on TranslationA Nonsense Mutation and its Effect on Translation
  • 11. Types of Base-Pair Substitution MutationsTypes of Base-Pair Substitution Mutations
  • 12.  Neutral mutations, which produce nodetectable change in the function of theprotein translated from the message It is a subset of missense mutations wherethe new codon codes for a differentamino acid which is chemically equivalentto the original one i.e Lys to Arg (proteinfunction is not affected)
  • 13.  Silent mutations are mutations in which abase pair change transforms a codon intoanother codon for the same amino acid,with no detectable change in the resultingprotein Frameshift mutations, which result whenthe reading frame of a gene is shifted dueto the addition or deletion of one or twomore base pairs in a gene It results in a non-functional protein
  • 14. Types of Base-Pair Substitution MutationsTypes of Base-Pair Substitution Mutations
  • 15.  Point mutations are of two classes: Forward mutations Reverse mutations Forward mutations cause the genotype tochange from wild-type to mutant A reversion is a mutational event thatchanges a mutant phenotype back towild-type
  • 16.  The effects of a mutation may be diminishedor abolished by a suppressor mutation(secondary or second site mutation) A suppressor mutation is a mutation at adifferent site from an original mutation thatdoes not result in a reversal of the originalmutation but instead masks or compensatesfor the effects of the initial mutation
  • 17.  There are two major classes of suppressormutations: Intragenic suppressors occur within the samemutated genemRNA codon aaWT 5’CGT3’ CGU Arg3’GCA5’Mut 5’AGT3’ AGU Ser3’TCA5’Intragenic suppressor5’AGA3’ AGA Arg3’TCT5’ Intergenic suppressors occur in different genes
  • 18. Mechanism of action of an intergenic nonsense suppressorMechanism of action of an intergenic nonsense suppressormutation that results from mutation of a tRNA genemutation that results from mutation of a tRNA gene
  • 19.  Mutation rates and mutation frequencies areterms describing the quantitative measure ofthe occurrence of mutations Mutation rate presents the probability of aparticular kind of mutation as a function oftime i.e. number per nucleotide pair pergeneration or per gene per generation ex:spontaneous mutation rate in Eukaryote is10-4to 10-6per gene/generation
  • 20.  Mutation frequency is the number ofoccurrences of a particular kind ofmutation expressed as the proportion ofcells or individuals in a population i.e. thenumber per 100,000 organisms or numberper 1 million gametes
  • 21.  Mutations arise in DNA spontaneously as aresult of natural cellular processes Looping-out during the DNA replicationcan lead to deletion of bases on thenewly synthesized strand or on thetemplate strand. This will lead to shifted frame on the DNA. Most spontanous errors are corrected bycellular repair systems
  • 22. Spontaneous generation of addition andSpontaneous generation of addition anddeletion mutants by DNA looping-outdeletion mutants by DNA looping-outerrors during replicationerrors during replication
  • 23.  Mutagenic chemicals or radiation cancreate induced mutations in DNA
  • 24.  Mutations in the genetic codeCan be induced in somatic cellsby:› Chemicals: cancerogen› Radiation: X-ray, UV› Some viruses Heredity - 5%

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