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排序方式: 共有82条查询结果,搜索用时 15 毫秒
1.
Linkage of the evolutionarily-related serum albumin and alpha-fetoprotein genes within q11-22 of human chromosome 4 总被引:9,自引:3,他引:6
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Albumin and alpha-fetoprotein are structurally related serum proteins, having a similar gene structure and, conceivably, a common evolutionary origin. To test their relative arrangement in the human genome, the serum albumin and alpha-fetoprotein genes were mapped by in situ hybridization of cloned human albumin or alpha-fetoprotein cDNA to human mitotic chromosome preparations. Analysis of cells hybridized with the serum albumin probe showed that 39% of cells exhibited grains on the proximal portion of the long arm of chromosome 4 (bands q11-22), with these grains comprising 30% of all labeled sites throughout these mitoses. Similarly, in cells hybridized with the alpha-fetoprotein probe, 39% of cells were observed to contain silver grains on 4q11-22, these grains constituting 20% of all labeled sites in these cells. These results demonstrate chromosomal localization and linkage of the serum albumin and alpha-fetoprotein genes within bands q11-22 of the long arm of human chromosome 4. 相似文献
2.
Compartmentation of glutamate metabolism in brain. Evidence for the existence of two different tricarboxylic acid cycles in brain 总被引:18,自引:9,他引:9
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1. (14)C from [1-(14)C]glucose injected intraperitoneally into mice is incorporated into glutamate, aspartate and glutamine in the brain to a much greater extent than (14)C from [2-(14)C]glucose. This difference for [1-(14)C]glucose and [2-(14)C]glucose increases with time. The amount of (14)C in C-1 of glutamate increases steadily with time with both precursors. It is suggested that a large part of the glutamate and aspartate pools in brain are in close contact with intermediates of a fast-turning tricarboxylic acid cycle. 2. (14)C from [1-(14)C]acetate and [2-(14)C]acetate is incorporated to a much larger extent into glutamine than into glutamate. An examination of the time-course of (14)C incorporated into glutamine and glutamate reveals that glutamine is not formed from the glutamate pool, labelled extensively by glucose, but from a small glutamate pool. This small glutamate pool is not derived from an intermediate of a fast-turning tricarboxylic acid cycle. 3. It is proposed that two different tricarboxylic acid cycles exist in brain. 相似文献
3.
We have compared the amino acid sequences of two low-molecular-weight avian apoproteins: apoVLDL-II from very low-density lipoproteins of hen plasma and apovitellenin I from hen egg yolk. The sequence of White Leghorn apoVLDL-II was derived from the nucleotide sequence of cloned apoVLDL-II DNA (Chan et al., 1980). The sequenator was used to determine the amino acid sequence of apovitellinin I from two breeds of hen (White Leghorn and Australorp). The sequences from the two breeds were not only identical, but they also completely matched the predicted sequence derived from the apoVLDL-II DNA sequence. The identity reported here establishes that this protein is transported intact from the blood to the egg yolk. 相似文献
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5.
Ligation of EcoRI endonuclease-generated DNA fragments into linear and circular structures. 总被引:89,自引:0,他引:89
Double-stranded DNA fragments terminated at their 5′-ends by the singlestranded sequence pA-A-T-T-, generated by digestion of DNA with EcoRI restriction endonuclease, were ligated with Escherichia coli polynucleotide ligase under various conditions of temperature, concentration and time. The linear and circular products of ligation were separated by electrophoresis in agarose gel and quantitated by densitometry. The rate of ligation of (EcoRI-cleaved) simian virus (SV40) DNA at a concentration of 100 μg/ml increased from 0 °C to 5 °C to 10 °C (6-fold increase overall); raising the temperature to 15 °C did not further increase the rate of ligation. At the appropriate DNA concentrations, the predominant products of ligation are either linear concatemers that are integral multimers of the starting DNA fragment, or covalently closed circular structures of the monomeric DNA fragment. Ligating a mixture of two different length DNA fragments gives rise to all of the possible expected recombinant molecules.Linear or circular products of ligation were predicted by consideration of the total concentration of DNA termini, i, and the local concentration of one terminus in the neighborhood of the other on the same DNA molecule, j. The parameter j is a function of the length of a DNA molecule, providing this length is greater than the random coil segment of DNA. Experimentally it was found that circular structures are formed in significant amounts only under conditions when the value of j is several times greater than that of i. When j = i, equal amounts of linear and circular products would be expected, but most of the molecules were ligated into linear concatemers. No circular structure of a DNA fragment whose contour length l (6 × 10−2 μm) is smaller than the random coil segment value b (7·17 × 10−2 μm) was observed, while circular structures of the dimer of the same molecule (12 × 10−2 μm) were detected. 相似文献
6.
The albumin gene family arose in a series of duplication events which gave rise to symmetry in its structure. The four genes are tandemly linked on human chromosome 4q in the order: 5'ALB-5'AFP-5'ALF-5'DBP-centromere, and their introns display a symmetrical and repetitive pattern that is shared by members of the gene family. These repetitive motifs provide an internal reference, allowing observations of evolutionary changes within a single line (human) of evolutionary descent. The four genes and three intergenic regions between them increase in size as they get closer to the centromere. An invasion by multiple repetitive DNA elements may account, in part, for this expansion. 相似文献
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8.
Peter E.M. Gibbs Werner F. Witke Achilles Dugaiczyk 《Journal of molecular evolution》1998,46(5):552-561
The serum albumin gene family is composed of four members that have arisen by a series of duplications from a common ancestor.
From sequence differences between members of the gene family, we infer that a gene duplication some 580 Myr ago gave rise
to the vitamin D–binding protein (DBP) gene and a second lineage, which reduplicated about 295 Myr ago to give the albumin
(ALB) gene and a common precursor to α-fetoprotein (AFP) and α-albumin (ALF). This precursor itself duplicated about 250 Myr
ago, giving rise to the youngest family members, AFP and ALF. It should be possible to correlate these dates with the phylogenetic
distribution of members of the gene family among different species. All four genes are found in mammals, but AFP and ALF are
not found in amphibia, which diverged from reptiles about 360 Myr ago, before the divergence of the AFP-ALF progenitor from
albumin.
Although individual family members display an approximate clock-like evolution, there are significant deviations—the rates
of divergence for AFP differ by a factor of 7, the rates for ALB differ by a factor of 2.1. Since the progenitor of this gene
family itself arose by triplication of a smaller gene, the rates of evolution of individual domains were also calculated and
were shown to vary within and between family members. The great variation in the rates of the molecular clock raises questions
concerning whether it can be used to infer evolutionary time from contemporary sequence differences.
Received: 28 February 1995 / Accepted: 6 October 1997 相似文献
9.
10.