ISSN:
1432-1432
Keywords:
Genetic Code
;
Codon Exclusion
;
Point Mutation
;
Base Replacement
;
Non-Randomness of Base Replacement
;
Amino Acid Substitution
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Using information from human hemoglobin variants, different hemoglobin chains, cytochrome c, insulin molecules, labile parts of humanγ-globulin, (ϰ-, λ-, and H-chains) and tobacco mosaic virus coat proteins, some aspects of point mutations were examined. The main results: 1. All recent hemoglobin variants characterized by one amino acid substitution can be explained by one single base replacement. Of the amino acid substitutions in the other proteins, many more can be accounted for in this way than expected if substitution occured at random. 2. Within the human hemoglobinα-, β-, γ-, andδ-cistrons, a number of codons can be excluded. 3. When origin and direction of base replacements are taken into account, transitions cytosine → thymine (C→T) and thymine → cytosine (T→C) turn out to occur much more often than expected if replacements would occur at random. They are also more frequent than the corresponding transitions guanine → adenine (G→A) and adenine → guanine (A→G). This trend can be observed in all cistrons examined. It cannot be explained by obvious biases in the ascertainment of amino acid substitutions. It points to a relationship between mutation and coding, that cannot be explained on the basis of our present knowledge of the molecular processes involved in replication, mutation, repair, and transscription. Transversions, on the other hand (replacements of a purine by a pyrimidine or vice versa) seem to occur at random. 4. There is no evidence for clustering of point mutations in the same or in neighbouring codons of the abnormal human hemoglobinα- andβ-cistrons.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01653962
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