mutation

Examples of mutation in the following topics:

• 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.

• 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.

• Altered Gene Expression in Cancer

  • Cancer, a disease of altered gene expression, is the result of gene mutations or dramatic changes in gene regulation.
  • There are many tumor suppressor genes in cells, but the one most studied is p53, which is mutated in over 50 percent of all cancer types.
  • Therefore, the mutation of p53 in cancer will dramatically alter the transcriptional activity of its target genes.
  • When mutated, proto-oncogenes can become oncogenes and cause cancer .
  • When mutated, proto-oncogenes can become oncogenes and cause cancer due to uncontrolled cell growth.

• Processes and Patterns of Evolution

  • Genetic diversity within a population comes from two main mechanisms: mutation and sexual reproduction.
  • Mutation, a change in the DNA sequence, is the ultimate source of new alleles, or new genetic variation in any population.
  • The genetic changes caused by mutation can have one of three outcomes:
  • Many mutations will have no effect on the fitness of the phenotype; these are called neutral mutations.
  • A mutation may produce a phenotype with a beneficial effect on fitness.

• Cell Signaling and Cell Growth

  • In addition, uncontrolled cell growth leads to cancer; mutations in the genes encoding protein components of signaling pathways are often found in tumor cells .
  • Mutations in these genes can result in malfunctioning signaling proteins.
  • The gene encoding RAS is an oncogene that was originally discovered when mutations in the RAS protein were linked to cancer.
  • Further studies have indicated that 30 percent of cancer cells have a mutation in the RAS gene that leads to uncontrolled growth.