mutations

• mutating a gene encoding an enzyme would cause a block in the metabolic pathway so the organism can no longer synthesize a needed nutrient. this mutant is called an auxotroph
• mutations are changes to the nucleic acid sequence
• germline mutations are mutations that originally occurred in gametes and therefore are heritable
• somatic mutations are mutations that occur in all cell types except gametes therefore are not heritable. all daughter cells will express the mutation and it is expressed as sectors where the size depends on the time of mutation
• base substitutions are single nucleotide changes as a result of point mutations
• insertion is the addition of base pairs during DNA replication usually resulting in a frameshift mutation
• deletion is the removal of base pairs during DNA replication usually resulting in a frameshift mutation
• transitions are purine-to-purine or pyrimidine-to-pyrimidine changes
• transversions are purine-to-pyrimidine changes or vice versa
• missense mutations occur when a codon change causes a change in an amino acid
• nonsense mutations occur when a sense codon changes into a stop codon resulting in a premature stop
• silent mutations occur when a codon change does not change the amino acid due to degeneracy of the genetic code
• frameshift mutations occur when insertion or deletion of base pairs alter the reading frame
• a large scale deletion mutation is the loss of genes
• duplification or amplification mutations increase the dosage of genes
• translocation mutations are caused by the interchanging of genetic parts from nonhomologous chromosomes
• inversion mutations are caused by reversing the orientation of a segment of the chromosome
• spontaneous mutations are naturally occurring and mainly caused by replication erros or spontaneous lesions
• spontaneous lesions include the depurination and deamination of bases
• induced mutations are caused by environmental or artificial mutagens that cause mutations at an increased rate
• mutagens can induce mutations by replacing, altering, or damaging a base
• base analogs mimic bases and incorporate into DNA causing mispairing during DNA replication
• wild type alleles are the normal form of the gene
• loss of function alleles are mutations that reduce gene function or expression
• gain of function alleles are mutations that enhance gene function or expression