ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Evolution
  • Springer  (5)
  • American Meteorological Society
  • 1995-1999
  • 1990-1994
  • 1970-1974  (5)
  • 1965-1969
  • 1973  (5)
Collection
Keywords
Publisher
Years
  • 1995-1999
  • 1990-1994
  • 1970-1974  (5)
  • 1965-1969
Year
  • 1
    Electronic Resource
    Electronic Resource
    Is the fixation of observable mutations distributed randomly among the three nucleotide positions of the codon? (1973)
    Springer
    Journal of molecular evolution 2 (1973), S. 123-136 
    Details
    ISSN: 1432-1432
    Keywords: Nucleotide Substitutions ; Evolution ; Codons ; Cytochromesc ; Hemoglobins ; Fibrinopeptides A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The distribution among the three nucleotide positions of the codons of 642 mutations fixed during the descent of 49 sequences of cytochromec was examined. This was compared to the distribution expected if the number of ways of getting a selectively acceptable amino acid alternative from a single nucleotide replacement at each coding position were random,i.e. proportional to the total number of ways of changing the encoded amino acid by a single nucleotide replacement at each coding position. It was found that the observed distribution was significantly different from random, there being 40% more mutations in the first coding position than in the second whereas one would have expected 10% more in the second than in the first. The probability of the result occurring by chance is 〈 10−6. The same test was made on the distribution of 347 mutations fixed in the descent of 19 sequences of alpha hemoglobin and 286 mutations fixed in the descent of 16 beta and 4 delta hemoglobins. The result for the alpha hemoglobins was a similar non-randomness but the probability of its occurring by chance rose to 0.005. The result for the beta-delta hemoglobins was in the same direction but was not significant (p = 0.3). The degree of non-randomness among the three genes in the distribution of fixations over the three nucleotide positions of their codons appears to be correlated (negatively) with their rates of evolution, the plasticity required of the molecule to adapt to new environments, and the recency of exploitation of opportunities for change in functional specificity provided by such processes as gene duplication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653992
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Are human hemoglobin variants distributed randomly among the positions? (1973)
    Springer
    Journal of molecular evolution 2 (1973), S. 181-186 
    Details
    ISSN: 1432-1432
    Keywords: Hemoglobin ; Evolution ; Mutation ; Fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The distribution of human hemoglobin variants has previously been studied by Vogel (1972) who concluded that the distribution was random although no statistical analysis was presented. This work points out that there are four biases in the data, one in the manner in which the number of variants is counted, another in the method by which they are detected and which favors charge changes, a third in the fact that for a few codons the same amino acid replacement may be brought about by two or three single nucleotide replacements, and a fourth in the non-random sampling procedure which favors variants producing clinical symptoms. Nevertheless, the distribution of beta hemoglobin variants is confirmed to be random as Vogel suggests. The alpha hemoglobin variants are distinctly non-randomly distributed, the best fit requiring that 69 of the alpha positions be considered invariable. The above biases could account for this result but other considerations combine to suggest the following: 1, about half of all alterations of alpha hemoglobin will not survive to sampling whereas nearly all beta variants can; 2, deleterious mutants that survive to sampling but are destined to be eliminated by selection are more likely to be observed in beta than in alpha hemoglobin; and 3, mutations destined to go to fixation are more likely to occur in beta than in alpha hemoglobin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653998
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Evolution of nucleic acid replication: The possible role of simple repeating sequence polypeptides therein (1973)
    Springer
    Journal of molecular evolution 2 (1973), S. 205-208 
    Details
    ISSN: 1432-1432
    Keywords: Nucleic Acid ; Evolution ; Growing Point ; Templating ; Alternating Sequence Polypeptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Our concept of nucleic acid replication does not explain the movement in that process—i.e., the existence of a socalled “growing point”. This omission may manifest itself in a failure to understand primitive nucleic acid replication. The latter may not be merely a “templating” process. Primitive nucleic acid replication is postulated to involve a particular type of peptide that establishes a “growing point”—a polypeptide in whichalternate amino acid residues are basic. Possible interactions of such a peptide with single and double stranded nucleic acid and its possible mode(s) of synthesis in a primitive environment are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01654001
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Fine structure of eyespots in tornarian larvae (Phylum: Hemichordata) (1973)
    Springer
    Cell & tissue research 142 (1973), S. 89-102 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptors ; Larva ; Hemichordate ; Ultrastructure ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The eyespots of tornariae of enteropneusts (Ptychodera flava from Hawaiian waters and an unknown species from southern California) were studied by electron microscopy. An ocellus is composed of two types of cells: sensory and supportive. The former is characterized by a bulbous cilium (with 9+2 axoneme) at its distal end, one or sometimes two arrays of microvilli from its sides below the cilium, and a basal axon. The latter features large, clear vesicles which presumably contained the reddish-orange pigment seen in the ocellus of a living larva. Five-day old tornariae of P. flava are positively phototactic. Both cilium and microvilli may function as photoreceptors. The tornarian ocellus studied is compared with eyespots of other invertebrates, and the evolutionary significance of its putative photoreceptors is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306706
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Collar cells in planula and adult tentacle ectoderm of the solitary coral Balanophyllia regia (anthozoa eupsammiidae) (1973)
    Springer
    Cell & tissue research 145 (1973), S. 57-74 
    Details
    ISSN: 1432-0878
    Keywords: Collar cells ; Planula ; Larva, Balanophyllia regia (coral) ; Sense organs ; Evolution ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The planula larva of the solitary coral Balanophyllia regia has an ectoderm of flagellate, diplosomal collar cells. The collar of these cells is composed of a ring of microvilli linked with mucus strands. Four types of flagellate gland cells, three types of nematocyst and spirocysts are present in the planula ectoderm. The function of these ectoderm cells is discussed. The mesogloeal muscular and packing tissues of the planula are briefly described. The tentacle of the adult coral, examined for comparison, has an ectoderm of flattened flagellate cells with a shallow collar. Collar cells similar to those of the planula are occasionally found on the tentacle and their function is not known. Independent sensory cells built on a modified collar cell plan with collar of thickened microvilli are common in the tentacle. These are quite separate from the three kinds of tentacular nematocyte. Distended glandular areas occur in the tentacle ectoderm. The flagellate tentacle gastrodermis, muscle and mesogloeal region are briefly described. The evolutionary significance of collar cell ectoderm in a planula is discussed and the occurrence of collar cells throughout the animal kingdom, reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307189
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...