| petite mutant | <molecular biology, organism> A class of yeast mutants, most studied in Saccharomyces cerevisiae. Mutants grow slowly and rely on anaerobic respiration: mitochondria, although present, have reduced cristae and are functionally defective (termed promitochondria). There are three types of petite mutant: (i) Segregational mutants that show Mendelian behaviour and result from mutations in mitochondrial genes located in the nucleus. (ii) Neutral petites, which are recessive genotypes and result from the complete absence of mitochondrial DNA. (iii) Suppressive petites, in which most of the mitchondrial DNA is lost (60-99%), though what remains is often amplified. (06 Oct 1997) |
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| mice, mutant strains | Mice bearing mutant genes which are phenotypically expressed in the animals. (12 Dec 1998) |
| minute mutant | <genetics, molecular biology> A class of recessive lethal mutants of Drosophila The heterozygotes grow more slowly, are smaller and less fertile than the wild type flies. There are about 40 loci that produce minute mutants. (18 Nov 1997) |
| cold-sensitive mutant | A mutant that is defective at low temperature but functional at normal temperature. Compare: temperature-sensitive mutant. (05 Mar 2000) |
| conditional-lethal mutant | A viral mutant that can replicate under some (permissive) conditions but not under other (restrictive or nonpermissive) conditions, the parent (wild type) strain being able to replicate under both conditions. See: suppressor-sensitive mutant, temperature-sensitive mutant. Synonym: conditional-lethal mutant. (05 Mar 2000) |
| conditionally lethal mutant | A viral mutant that can replicate under some (permissive) conditions but not under other (restrictive or nonpermissive) conditions, the parent (wild type) strain being able to replicate under both conditions. See: suppressor-sensitive mutant, temperature-sensitive mutant. Synonym: conditional-lethal mutant. (05 Mar 2000) |
| constitutive mutant | An organism with a mutation in a regulatory gene, so that the genes which its flawed regulatory product are supposed to suppress become constitutive genes, or impossible to turn off. Thus, the products of the uncontrolled genes are produced to excess. (09 Oct 1997) |
| mutant | <biology, genetics> Refer to an organism, population, gene, or chromosome, etc. Which differs from the corresponding wild type by one or more mutations. (13 Nov 1997) |
| mutant gene | A gene that has been changed from an ancestral type, not necessarily in the current generation. See: mutant, mutation. (05 Mar 2000) |
| homeotic mutant | <molecular biology> A mutant in which one body part, organ or tissue, is transformed into another part normally associated with another segment. Examples are the antennapedia and bithorax mutants of Drosophila. (18 Nov 1997) |
| host range mutant | A mutant of phage or animal virus that grows normally in one of its host cells, but has lost the ability to grow in cells of a second host type. (18 Nov 1997) |
| silent mutant | A mutant that is not phenotypically manifest. Synonym: silent mutant. (05 Mar 2000) |
| suppressor-sensitive mutant | A conditionally lethal, host range, bacteriophage mutant that produces nonsense codons and can replicate only in a host bacterium able to translate the nonsense codon; the mutation's effects are lethal (i.e., prevent replication of the virus) in a bacterium without such a suppressor mechanism. (05 Mar 2000) |
| deficiency mutant | Mutant with a nutritional requirement not present in the wild type organism. Synonym: defective organism, deficiency mutant. (05 Mar 2000) |
| disjunction mutant | Drosophila mutant in which chromosomes are partitioned unequally between daughter cells at meiosis, as a result of nondisjunction. (18 Nov 1997) |