Genetics Key Terms 7

The concept that organisms in some way "select" or "direct" the mutation of their genes in order to adapt to a particular environmental pressure.

A bacterial assay developed by Bruce Ames to detect mutagenic compounds; it assesses reversion to histidine independence in the bacterium Salmonella Typhimurium.

A purine or pyridimine base that differs structurally from one normally used in biological systems whose chemical behavior is the same. Used experimentally to provide detection during analysis, for example, 5-bromouracil, which "looks like" thymidine, substitutes for it, and can be detected because of its increased mass.

A triplet of nucleotides that specifies a particular amino acid or a start or stop signal in the genetic code. Sixty-one codons specify the amino acids used in proteins, and three codons, called stop codons, signal termination of growth of the polypeptide chain.

Chemical affinity between nitrogenous bases of nucleic acid strands as a result of hydrogen bonding. Responsible for the base-pairing between the strands of the DNA double helix and between DNA and RNA strands during genetic expression in cells and during the use of molecular hybridization techniques.

A mutation that is expressed only under a certain condition, that is, a wild-type phenotype is expressed under certain (permissive) conditions and a mutant phenotype under other (restrictive) conditions.

Two related forms of muscular dystrophy. They are recessive, X-linked conditions. DMD is most severe with the rapid progression of muscle degeneration and involvement of the heart and lungs. BMD progresses slowly. Gene responsible is dystrophin that contains about 2.5 million base pairs.

A statistical test that demonstrated that bacterial mutations arise spontaneously, in contrast to being induced by selective agents.

Gene responsible is FMR-1. It may contain several to several thousand copies of trinucleotide sequence CGG located in the 5'-untranslated region of the gene.

A mutational event leading to the insertion of one or more base pairs in a gene, shifting the codon reading frame in all codons that follow the mutational site.

a mutation that produces a phenotype different from that of the normal allele and from any loss of function alleles.

The deoxynucleotide triplets that encode the 20 amino acids or specify termination of translation

Mutations occuring in gametes

A somatic cell containing nuclei from two different sources.

TAutosomal dominant condition. The repeats lie within the coding portion of the gene. Mutant huntingtin protein to contain an excess of glutamine residues.

TBD

TBD

A mutation that may interrupt a process that is essential to the survival of the organism.

A mutation that reduces or eliminates the function of the gene product.

A form of incision repair of DNA in which the repair mechanism is able to distinguish between the strand with the error and the strand that is correct.

A mutation that alters a codon to that of another amino acid and thus results in an alteration in the translation product.

A mutation with no immediate adaptive significance or phenotypic effect.

A mutation that changes codon encoding an amino acid into a termination codon, leading to premature termination during translation of mRNA.

Result in complete loss of function

A mutation that can be mapped to a single locus. At the molecular level, a mutation that results in the substitution of one nucleotide for another.

A linear sequence of codons in a nucleic acid

a loop that occurs in the template strand during replication, DNA polymerase may miss the looped-out nucleotides, and a small deletion in the new strand will be introduced. Is common in regions containing repeated sequences.

TBD

If the point mutation alters a codon but does not result in a change in the amino acid at that position in the protein it is considered a silent mutation.

Link between XP and excision repair was further strengthened by studies using somatic cell hybridization.

A nonheritable mutation occurring in a somatic cell.

A mutation that is not induced by a mutagenic agent.

A reversible isomerization in a molecule, brought about by a shift in the location of a hydrogen atom. In nucleic acids, tautomeric shfits in the bases of nucleotides can cause changes in other bases at replication and are a source of mutations.

A conditional mutation that produces a mutant phenotype at one temperature range and a wild-type phenotype at another.

A mutational event in which one purine is replaced by another or one pyrimidine is replaced by another.

A mutational event in which a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine

TBD