nonsense mutation

(redirected from Premature stop codon)
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sup·pres·sor mu·ta·tion

1. a second mutation that alters the anticodon in a tRNA so that it can recognize a nonsense (stop) codon, thus suppressing termination of the amino acid chain. Compare: amber mutation, ochre mutation, umber mutation.
2. genetic changes such that the effect of a m. in one place can be masked by a second m. in another location. There are two types: intergenic suppression (occurring in a different gene) and intragenic suppression (occurring in the same gene but at a different site).
Synonym(s): nonsense mutation

nonsense mutation

a mutation in which one of the three terminator codons in the mRNA used to signal the end of a polypeptide appears in the middle of a genetic message and causes premature termination of transcription and release of incomplete, generally nonfunctional polypeptides from the ribosome. The three types are amber mutation, ochre mutation, opal mutation.

nonsense mutation

A POINT MUTATION which changes a CODON that specifies an amino acid into a termination codon-one that marks the position where translation of a messenger RNA sequence should stop. The result is a gene with a segment lopped off. Such a gene will code for a protein that may have missing amino acids and may thus be functionally defective.

nonsense mutation

an alteration in a DNA POLYNUCLEOTIDE CHAIN that results in a NONSENSE CODON when transcribed on to mRNA.


1. a nucleotide change, including base substitutions, insertions or deletions in DNA, or RNA in the case of some viruses, that gives rise to the mutant phenotype.
2. an animal exhibiting such change. Called also a sport.

back mutation
see reverse mutation (below).
base substitution mutation
may be a transition in which a purine-pyrimidine pair is substituted by the other purine-pyrimidine pair, or transversion in which a purine-pyrimidine pair is replaced by one of the two pyrimidine pairs.
chain termination mutation
one in which the new base sequence introduces a stop codon and thereby prematurely terminates synthesis of the polypeptide; the three mutations are also called amber (UAG), ochre (UAA) and opal (UGA).
deletion mutation
one produced by loss of nucleotides from a DNA sequence.
frame shift mutation
occur as a result of either the insertion of a new base pair or the deletion of a base pair or a block of base pairs from the DNA base sequence; these, unless they occur in 3 or multiples of 3, are most serious in that the message to the right of the frame shift is garbled.
leaky mutation
one in which the amino acid substitution only partially disrupts the function of the protein; in bacteria this is usually manifested by reduced growth rate.
mis-sense mutation
one causing an amino acid substitution in the protein.
nonsense mutation
one in which a stop codon is substituted for a codon that specifies an amino acid.
operator constitutive mutation
one or more base changes in the operator region (originally defined for the lactose operon) which stop the repressor protein from tightly binding to sequence such that it is less effective in preventing RNA polymerase from inhibiting transcription.
point mutation
a single changed base pair in the DNA of an organism which may be a base substitution, base insertion or base deletion.
mutation rate
the frequency of mutations in the population over time.
repressor-constitutive mutation
in regulation of gene expression, a mutation in the repressor protein that decreases the binding affinity of the repressor protein for the operator which leaves the gene permanently turned on.
reverse mutation
one in which the wild-type phenotype is restored; such organisms are called revertants. Called also back mutation, reversion mutation.
second-site mutation
see suppressor mutation.
silent mutation
one in which there is a base change but because of the redundancy of the genetic code the same amino acid is coded, or one in which there is an amino acid substitution in the protein which has no detectable effect on the phenotype.
somatic mutation
a change in the DNA sequence that occurs in somatic cells, i.e. not gametes. The mechanism underlying the generation of diversity of antigen recognition by immunoglobulins and T cell receptor molecules. The fundamental cause of cancer, in which the mutation occurs spontaneously or is induced by carcinogens, such as sunlight, chemicals or viruses.
suppressor mutation
a particular type of reversion mutation in which a mutation at a second site restores the original phenotype; most simply a mutation produced by a base deletion may be restored to wild type by a proximate but independent base substitution. Called also second-site mutation.
temperature-sensitive (ts) mutation
one in which there is an altered protein that is active at one temperature, typically 86°F (30°C) and inactive at a higher temperature, usually 104 to 108°F (40 to 42°C), e.g. ts mutant virus and bacteria.
transdominant mutation
occur in genes producing diffusible products, in contrast to cis-dominant mutation in which mutations occur in regulatory sequences that are recognized by other proteins.
transition mutation
one in which the base change does not change the pyrimidine-purine orientation. See also base substitution mutation (above).
transposition mutation
one produced by the insertion of a transposable genetic element.
transversion mutation
one in which the purine-pyrimidine orientation is changed to pyrimidine-purine or vice versa. See also base substitution mutation (above).
References in periodicals archive ?
At the protein level, the readthrough becomes translated into 5 extra amino acids followed by a premature stop codon.
In test-tube studies, they demonstrated that human cells with a CFTR gene containing a premature stop codon could occasionally construct the full protein if treated with aminoglycosides.
Impressed by the cystic fibrosis studies, Sweeney tried the antibiotics on mouse muscle cells containing a dystrophin gene with a premature stop codon.
2895-2898de1GTTC) (25), which causes a frameshift at amino acid 965 in exon 21 with a putative premature stop codon at amino acid position 994 in exon 22 (p.
The excision of exon 20 in the DUOX2 mRNA might generate a frameshift with a putative premature stop codon in exon 21, which encodes a grossly truncated protein of 885 amino acids.
Obviously, the premature stop codon that we identified would have effects on the coagulation pathway vastly different from those of a factor V Leiden mutation, as well as significantly different clinical and therapeutic implications.
This effect leads to a reading frameshift that introduces a premature stop codon 12 amino acids downstream in exon 12 (see Fig.
The occurrence of such a premature stop codon causes the synthesis of a truncated protein by arresting translation at the site of the nonsense mutation.
A microdeletion of a base pair was detected on one of the two alleles of the X chromosomes, [delta]-A 409 in exon 5 of the gp91-phox gene (CYBB), which led to a shift of the reading frame and to a premature stop codon at position amino acid 139, Va1139 [right arrow] stop.
All transmission involved infections by viruses with the pre-core premature stop codons, which reflected changes in viral genotypes caused by increased migration in UK healthcare workers.
Nonsense mutations were distributed across the span of the 79 exons of the dystrophin gene, with no mutational hotspots identified, and represented all three types of premature stop codons.
Nonsense mutations are single-point alterations in the genetic code that introduce premature stop codons in RNA, which halt the translation process, producing a shortened, non-functional protein.

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