mutation

Examples of mutation in the following topics:

• Complementation

  • These strains are true breeding for their mutation.
  • When this occurs, each strain's haploid supplies a wild-type allele to "complement" the mutated allele of the other strain's haploid, causing the offspring to have heterozygous mutations in all related genes.
  • Since the mutations are recessive, the offspring will display the wild-type phenotype.
  • In other words, if the combination of two haploid genomes containing different recessive mutations yields a mutant phenotype, then there are three possibilities: Mutations occur in the same gene; One mutation affects the expression of the other; One mutation may result in an inhibitory product.
  • If the combination of two haploid genomes containing different recessive mutations yields the wild type phenotype, then the mutations must be in different genes.

• Mutation

  • Mutations are caused by radiation, viruses, transposons, and mutagenic chemicals.
  • This synthetic primer contains the desired mutation and is complementary to the template DNA around the mutation site so it can hybridize with the DNA in the gene of interest.
  • The mutation may be a single base change (a point mutation), multiple base changes, deletion, or insertion.
  • The copied gene contains the mutated site.
  • The distribution of fitness effects of mutations in vesicular stomatitis virus.

• Gene Flow and Mutation

  • Mutations are changes to an organism's DNA and are an important driver of diversity in populations.
  • Species evolve because of the accumulation of mutations that occur over time.
  • The appearance of new mutations is the most common way to introduce novel genotypic and phenotypic variance.
  • A mutation has caused this garden moss rose to produce flowers of different colors.
  • Explain how gene flow and mutations can influence the allele frequencies of a population

• Proto-oncogenes

  • Proto-oncogenes normally regulate cell division, but can be changed into oncogenes through mutation, which may cause cancers to form.
  • Proto-oncogenes are normal genes that, when mutated in certain ways, become oncogenes: genes that cause a cell to become cancerous.
  • If a cell cannot reproduce, the mutation is not propagated and the damage is minimal.
  • Occasionally, however, a gene mutation causes a change that increases the activity of a positive regulator.
  • If the resulting daughter cells are too damaged to undergo further cell divisions, the mutation would not be propagated and no harm would come to the organism.

• DNA Repair

  • Repair mechanisms can correct the mistakes, but in rare cases mistakes are not corrected, leading to mutations; in other cases, repair enzymes are themselves mutated or defective.
  • Such mutations may be of two types: induced or spontaneous.
  • Mutations may have a wide range of effects.
  • Some mutations are not expressed; these are known as silent mutations.
  • Point mutations are those mutations that affect a single base pair.

• Defining Population Evolution

  • Each of these characteristics is the result of a mutation, or a change in the genetic code.
  • Mutations occur spontaneously, but not all mutations are heritable; they are passed down to offspring only if the mutations occur in the gametes.
  • These heritable mutations are responsible for the rise of new traits in a population.
  • As mutations create variation, natural selection affects the frequency of that trait in a population.
  • Mutations that confer a benefit (such as running faster or digesting food more efficiently) can help that organism survive and reproduce, carrying the mutation to the next generation.

• Genome Evolution

  • Processes such as mutations, duplications, exon shuffling, transposable elements and pseudogenes have contributed to genomic evolution.
  • Mutation rates differ between species and even between different regions of the genome of a single species .
  • Spontaneous mutations often occur which can cause various changes in the genome.
  • Mutations can result in the addition or deletion of one or more nucleotide bases.
  • Chromosomal mutations over time can accumulate and promote diversity and evolution if a produced trait is favorable.

• Vaccines and Immunity

  • The danger of using live vaccines, which are usually more effective than killed vaccines, is low, but significant since the possibility that these viruses will revert to their disease-causing form by back mutations is still present.
  • Back mutations occur when the vaccine undergoes mutations in the host such that it readapts to the host and can again cause disease, which can then be spread to other humans in an epidemic.
  • This type of scenario happened as recently as 2007 in Nigeria where mutations in a polio vaccine led to an epidemic of polio in that country.
  • Some vaccines are in continuous development because certain viruses, such as influenza and HIV, have a high mutation rate compared to other viruses and normal host cells.
  • Other viruses, such as those that cause the childhood diseases measles, mumps, and rubella, mutate so infrequently that the same vaccine is used year after year.

• Coupling Specific Genes to Specific Organisms Using PCR

  • PCR allows for the amplification and mutation of DNA and allowing researchers to study very small samples.
  • Polymerase chain reaction (PCR) is a useful technique for scientists, because it allows for the amplification and mutation of DNA.
  • Through PCR, the original DNA is essentially limitless, allowing scientists to induce various mutations in different genes for further study.
  • Through site-directed mutagenesis or customized primers, individual mutations in DNA can be made.
  • Describe how polymerase chain reaction (PCR) allows for the amplification and mutation of DNA and enables researchers to study very small samples

• Tumor Suppressor Genes

  • A cell that carries a mutated form of a negative regulator might not be able to halt the cell cycle if there is a problem.
  • Mutated p53 genes have been identified in more than one-half of all human tumor cells.
  • Even if a partially-functional p53 does identify the mutations, it may no longer be able to signal the necessary DNA repair enzymes.
  • Mutated p53 might lose its ability to trigger p21 production.
  • At the completion of this shortened cell cycle, two daughter cells are produced that have inherited the mutated p53 gene.