Biomaterial Database

Evidence for high-frequency allele loss at the aprt locus in TK6 human lymphoblasts. 1993

L E Smith, and A J Grosovsky

Environmental Toxicology Graduate Program, University of California, Riverside 92521.

The aprt locus in TK6 human lymphoblasts has been previously shown to have an unusual mutation frequency (5 x 10(-8) and a gene dosage of 2. Measurements of mutation rate (1.2 x 10(-9)) reported here, confirm the mutation-frequency observations. These results are not easily accommodated by models of the gene as functionally homozygous or heterozygous. Characterization of all exon and intron sequences identified no polymorphism which could distinguish two heterozygous aprt alleles. Furthermore, autoradiographs of 16 spontaneous APRT- mutants demonstrate a variety of unique sequences. If aprt were heterozygous, wild-type sequence from the alternate allele would be observed at positions where mutations have occurred. These observations cannot be explained by conventional loss of heterozygosity in which the same mutated allele would be repeatedly recovered. We therefore propose that aprt is a functionally homozygous locus. APRT- mutants may arise by conventional mutation of one allele, and high-frequency loss or conversion of the alternate allele.

UI	MeSH Term	Description	Entries
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D012150	Polymorphism, Restriction Fragment Length	Variation occurring within a species in the presence or length of DNA fragment generated by a specific endonuclease at a specific site in the genome. Such variations are generated by mutations that create or abolish recognition sites for these enzymes or change the length of the fragment.	RFLP,Restriction Fragment Length Polymorphism,RFLPs,Restriction Fragment Length Polymorphisms
D002460	Cell Line	Established cell cultures that have the potential to propagate indefinitely.	Cell Lines,Line, Cell,Lines, Cell
D004252	DNA Mutational Analysis	Biochemical identification of mutational changes in a nucleotide sequence.	Mutational Analysis, DNA,Analysis, DNA Mutational,Analyses, DNA Mutational,DNA Mutational Analyses,Mutational Analyses, DNA
D006579	Heterozygote	An individual having different alleles at one or more loci regarding a specific character.	Carriers, Genetic,Genetic Carriers,Carrier, Genetic,Genetic Carrier,Heterozygotes
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000228	Adenine Phosphoribosyltransferase	An enzyme catalyzing the formation of AMP from adenine and phosphoribosylpyrophosphate. It can act as a salvage enzyme for recycling of adenine into nucleic acids. EC 2.4.2.7.	AMP Pyrophosphorylase,Transphosphoribosidase,APRTase,Phosphoribosyltransferase, Adenine,Pyrophosphorylase, AMP
D001402	B-Lymphocytes	Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.	B-Cells, Lymphocyte,B-Lymphocyte,Bursa-Dependent Lymphocytes,B Cells, Lymphocyte,B Lymphocyte,B Lymphocytes,B-Cell, Lymphocyte,Bursa Dependent Lymphocytes,Bursa-Dependent Lymphocyte,Lymphocyte B-Cell,Lymphocyte B-Cells,Lymphocyte, Bursa-Dependent,Lymphocytes, Bursa-Dependent
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D015139	Blotting, Southern	A method (first developed by E.M. Southern) for detection of DNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.	Southern Blotting,Blot, Southern,Southern Blot