Food selection, food-seeking patterns and hunting success of captive Goosanders Mergus merganser and Red-breasted Mergansers M. serrator in relation to the behaviour of their prey

Food selection and food-seeking behaviour of hand-raised Goosanders Mergus merganser and Red-breasted Mergansers M. serrator were tested in experimental situations. When different combinations of two species of fish were presented simultaneously to hungry birds in a small trough where the prey was easily and equally available, neither duck species showed any preferences in prey selection. However, when these same fish species were presented to satiated birds, they showed definite preferences; the most preferred species were baltic salmon and brown trout followed in decreasing order by minnow, whitefish, sculpin, burbot and river lamprey. This was also the case when combinations of five to seven species were presented. However, under semi-natural conditions in a stream tank, the number of each species offish caught was related to their escape behaviour, not to the previously determined predator preferences. When salmon and minnows of different size were presented to hungry birds, they selected the larger fish regardless of species. In contrast, when satiated, they preferred small fish over large fish. Under the experimental conditions, the use of certain elements of foraging behaviour clearly differed between the two bird species: Mergus serrator spent more time hunting underwater than did M. merganser. Results are discussed in relation to the predator-prey situation existing under natural conditions in northern Swedish rivers.     

Mung bean nuclease cleavage of a dA + dT-rich sequence or an inverted repeat sequence in supercoiled PM2 DNA depends on ionic environment

We have determined the nucleotide sequences around two alternative sites cleaved in supercoiled PM2 DNA by single-strand-specific mung bean nuclease in different ionic environments. In 10 mM Tris-HC1 (pH 7.0, 37 degrees C), the major site is a dA+dT-rich sequence which maps with a known early denaturation region at 0.75 map units. About 30 cleavages occurred in a 135 bp region. Cleavages were largely excluded at (dA)n . (dT)n (n = 3-7) sequences. Cleavage patterns of this type have not been previously observed in dA+dT-rich sequences. With the addition of 0.1 M NaC1 the major alternative site occurred in a hyphenated inverted repeat sequence 500 bp away (0.70 map units) and did not map to an early denaturation region. One major and 4 minor cleavages occurred in the region between the repeats, suggesting that a hairpin containing at most a 12 bp stem and 10 base loop is recognized. The basis for nuclease recognition of the dA+dT-rich sequence is not clear. The differences in the sequences and cleavage patterns at the alternative sites indicate that their secondary structures differ.     

Sequence heterogeneity and anomalous electrophoretic mobility of kinetoplast minicircle DNA from Leishmania tarentolae

Several unit-length minicircles from the kinetoplast DNA of Leishmania tarentolae were cloned into pBR322 and into M13 phage vectors. The complete nucleotide sequences of three different partially homologous minicircles were obtained. The molecules contained a region of approx. 80% sequence homology extending for 160–270 bp and a region unique to each minicircle. A 14-mer was found to be conserved in all kinetoplast minicircle sequences reported to date. The frequency distributions of various minicircle sequence classes in L. tarentolae were obtained by quantitative gel electrophoresis and by examination of the “T ladder” patterns of minicircles randomly cloned into M13 at several sites. By these methods we could assign approx. 50% of the total minicircle DNA into a minimum of five sequence classes. A sequence-dependent polyacrylamide gel migration abnormality was observed with several minicircle fragments both cloned and uncloned. The abnormality was dependent on the presence of a portion of the conserved region of the minicircle.     

Evidence that populations of Dictyostelium single-copy mRNA transcripts carry common repeat sequences.

Two recombinant plasmids, M4 and KH10, carrying Dictyostelium DNA inserted into the Eco RI restriction endonuclease site of pMB9 by poly(dA)-poly(dT) tailing, were selected for study because they are complementary to abundant mRNA populations from Dictyostelium. Both plasmids have been shown to hybridize a heterogeneous size class of mRNAs which, in the case of KH10, comprise 5-10% of the pulse-labeled poly(A)+ RNA from vegetative cells. Analysis of the sequence organization of the two pieces of Dictyostelium DNA shows that they consist mostly of single-copy sequences with a short DNA sequence which is repeated in the genome and interspersed with single-copy DNA. These and other results suggest that the majority of the hybridization of pulse-labeled mRNA to M4 and KH10 is to the short "repeated" DNA sequences. In the genome, members of these repeat families appear to be transcribed onto a population of different single-copy mRNAs. Additional results show that M4 DNA contains a sequence which is entirely complementary to a discrete mRNA.     

Poly(dG)-poly(dC) DNA appears shorter than poly(dA)-poly(dT) and possibly adopts an A-related conformation on a mica surface under ambient conditions

Three types of DNA: approximately 2700 bp polydeoxyguanylic olydeoxycytidylic acid [poly(dG)-poly(dC)], approximately 2700 bp polydeoxyadenylic polydeoxythymidylic acid [poly(dA)-poly(dT)] and 2686 bp linear plasmid pUC19 were deposited on a mica surface and imaged by atomic force microscopy. Contour length measurements show that the average length of poly(dG)-poly(dC) is approximately 30% shorter than that of poly(dA)-poly(dT) and the plasmid. This led us to suggest that individual poly(dG)-poly(dC) molecules are immobilized on mica under ambient conditions in a form which is likely related to the A-form of DNA in contrast to poly(dA)-poly(dT) and random sequence DNA which are immobilized in a form that is related to the DNA B-form.     

Structure and organization of the highly repeated and interspersed 1.3 kb EcoRI-Bg1II sequence family in mice.

EcoRI digestion of total mouse DNA yields a prominant 1.3 kb fragment amounting to between 1 and 2% of the mouse genome. The majority of the 1.3 kb EcoRI fragments have a single Bg1II site 800 bp from one end. This EcoRI-Bg1II sequence family shows HindIII and HaeIII sequence heterogeneity. We have cloned representatives of the EcoRI-Bg1II gene family in Charon 16A and studied their structure and organization within the genome. The cloned 1.3 kb fragments show the expected restriction enzyme patterns as well as additional heterogeneity. Representatives of the EcoRI-Bg1II sequence family were found to be interspersed throughout the mouse genome as judged by CsCl density gradient centrifugation experiments. Family members were also found to be organized in higher order repeating units. Homologous sequences were also found in other rodent species including rat and Chinese hamster. Cross hybridization between a cloned 1.3 kb mouse fragment and a cloned CHO repeated sequence is of special interest since the latter has been shown to contain sequences homologous to the Human A1uI family by nucleotide sequencing.     

Structural analysis of alphoid DNA of primates. I. Heterogeneity of nucleotide sequence of alphoid repeats in human DNA

The nucleotide sequence of two cloned fragments of human alphoid DNA was established. These fragments were earlier characterized in our laboratory as molecular markers of the 3rd (pHS05) and 11th (pHS53) chromosomes. Fragment pHS53 (2546 bp) contains alphoid repeats tandemly arranged and organized into three highly homologous pentamers. The heterogeneity of monomeric sequences within individual pentamers reaches 24-33%. Structural analysis of EcoRI subfragment pHS05 showed that this alphoid tetramer consists of two dimers 340 bp long. These dimers differ up to 16% from each other and from the so-called consensus sequence of the EcoRI-340 bp-restriction fragments family reported earlier by Wu and Manuelidis. The primary structure of four cloned fragments of EcoRI-340 bp-family was established. The data show that human alphoid DNA is highly heterogeneous. This conclusion is opposite to the view suggesting that alphoid DNA is a highly homogeneous class of reiterated sequences of the human genome.     

Polynucleotide sequences in eukaryotic DNA and RNA that form ribonuclease-resistant complexes with polyuridylic acid

When annealed with synthetic polynucleotides and treated with ribonuclease under appropriate conditions, poly(U) forms the ribonuclease-resistant complexes poly(rA) · poly(U) (1:1), poly(dA) · 2poly(U) (1:2) and poly · (dA)poly(dT) · poly(U) (1:1:1). This forms the basis of a quantitative assay of poly(rA), poly(dA) and poly(dA) · poly(dT) sequences in unlabelled nucleic acids. Using this assay, duck haemoglobin messenger RNA is shown to contain a poly(rA) sequence approximately 100 nucleotides long.Eukaryotic DNAs contain small amounts of sequences that react with poly(U). In the case of duck DNA, these sequences are considerably shorter than the mRNA-associated sequences and are interspersed widely with other sequences. It is concluded that if duck DNA does contain poly(dA) sequences corresponding to mRNA-associated poly(rA) sequences, there are fewer than 8000 of these per haploid genome.     

Organization of gene and non-gene sequences in micronuclear DNA of Oxytricha nova.

In order to study the derivation of the macronuclear genome from the micronuclear genome in Oxytricha nova micronuclear DNA was partially digested with EcoRI, size fractionated, and then cloned in the lambda phage Charon 8. Clones were selected a) at random b) by hybridization with macronuclear DNA or c) by hybridization with clones of macronuclear DNA. One group of these clones contains only unique sequence DNA, and all of these had sequences that were homologous to macronuclear sequences. The number of macronuclear genes with sequences homologous to these micronuclear clones indicates that macronuclear sequences are clustered in the micronuclear genome. Many micronuclear clones contain repetitive DNA sequences and hybridize to numerous EcoRI fragments of total micronuclear DNA, yielding similar but non-identical patterns. Some micronuclear clones containing these repetitive sequences also contained unique sequence DNA that hybridized to a macronuclear sequence. These clones define a major interspersed repetitive sequence family in the micronuclear genome that is eliminated during formation of the macronuclear genome.     

Molecular cloning and nucleotide sequence of the cDNA for sperm-specific lactate dehydrogenase-C from mouse.

Mouse sperm-specific lactate dehydrogenase-C (LDH-C) cDNA was cloned and sequenced from lambda gt11 expression library. The LDH-C cDNA insert of 1236 bp consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (113 bp) non-coding regions, and the poly(A) tail (70 bp). The Northern blot analysis of poly(A)-containing RNAs from mouse testes and liver indicates that the LDH-C gene is expressed in testes but not in liver, and that its mRNA is approx. 1400 nucleotides in length. The nucleotide and amino acid sequences of the mouse LDH-C cDNA show 73% and 72% homologies, respectively, with those of the mouse LDH-A. The Southern blot analysis of genomic DNAs from mouse liver and human placenta indicates the presence of multiple LDH-C gene-related sequences.     

The Flexibility of Alternating dA—dT Sequences

Abstract

The flexibility of alternating poly (dA—dT) has been investigated by the technique of transient electric dichroism. Rotational relaxation times, which are very sensitive to changes in the end-to-end length of flexible polymers, are determined from the field free dichroism decay curves of four, well defined fragments of poly (dA—dT) ranging in size from 136 to 270 base pairs. Persistence lengths, calculated from the results of Hagerman and Zimm (Biopolymers (1981) 29, 1481–1502), are in the range 200–250 A. This makes alternating dA—dT sequences about twice as flexible as naturally occurring, “random” sequence DNA. Considering a bend around a nucleosome, for example, this difference in persistence length translates to an energy difference between poly (dA—dT) and random sequence DNA of 0. 17 kT/base pair or 1 kcal per 10 base pair stretch. This energy difference is sufficiently large to suggest that dA—dT sequences could serve as markers in DNA packaging, for example, at sites where DNA must tightly bend to accommodate structures.     

Characterization of a major tandemly repeated DNA sequence (RBMII) prevalent among many species of waterfowl (Anatidae).

We have investigated the evolution of a 190 base pair tandemly repeated DNA sequence (RBMII) in 27 different species of waterfowl. In this paper we show that the RBMII sequence is present in many species belonging to 7 of the 11 Anatid tribes. Inter- and intra-tribal differences in repeat presence indicate that, although the RBMII sequence has been maintained among widely divergent species, it is rapidly evolving. Restriction enzyme analyses suggest very different hierarchical repeat organizations among different species. DNA sequence comparisons of 32 cloned monomer units from five different species revealed what appears to be a nonrandom distribution of sequence divergence, as well as large differences (up to 25-fold) in intraspecific sequence variation between relatively closely related species.     

Organization of delta-crystallin genes in the chicken.

Double-stranded DNA was synthesized from delta-crystallin mRNA prepared from lens fibers of 15-day-old chick embryos and cloned at the Pst I site of the plasmid pBR322. Using the cloned cDNA and single-stranded cDNA as hybridization probes, a number of genomic DNA fragments containing delta-crystallin gene sequences have been cloned from the partial and complete EcoRI digests of chick brain DNA. One of the clones from the partial digests contains a DNA fragment that consists of four EcoRI fragments of 7.6 kb, 4.0 kb, 2.6 kb, and 0.8 kb. The gene sequences reside in the (5')7.6 kb - 0.8 kb - 4.0 kb (3') fragments. Electron microscopy has provided evidence that the cloned DNA fragment includes the entire gene sequences complementary to delta-crystallin mRNA except for the 3' terminal poly(A) tail, and that the delta-crystallin gene is interrupted by at least 13 intervening sequences. Another clone contains a genomic fragment that consists of two EcoRI fragments of 3.0 kb and 11 kb. The DNA fragment in the latter clone represents a different delta-crystallin gene, as judged by restriction endonuclease mapping and by electron microscopy.     

Inhibition of DNA replication by berenil in plasmids containing Poly(dA)poly(dT) sequences

The effect of berenil on plasmid DNA replication was studied on pBR322-derived plasmids containing poly(dA)poly(dT) sequences. In comparison to the parental plasmid pBR322, plasmid pKH47 harboring 100 bp of poly(dA)poly(dT) at the PvuII site showed a decrease in plasmid yield in the presence of berenil. This effect was also observed in pVL26, a related plasmid in which the location of the poly(dA)poly(dT) region had been shifted to the EcoRV site in pBR322. [(3)H]Thymidine incorporation experiments indicated that DNA synthesis may be affected in these plasmids in the presence of the drug. Bromodeoxyuridine incorporation experiments coupled to Cs(2)SO(4) equilibrium density gradient centrifugation indicated that the lower plasmid yield was due to an inhibition of DNA replication by berenil. We have also found that berenil induces DNA degradation in plasmids containing the homopolymer. Our studies strongly suggest that the effect of berenil on plasmid replication and DNA stability results from its binding to the poly(dA)poly(dT) region present in these plasmids. Moreover, we have found a correlation between the position of the poly(dA)poly(dT) region and this inhibitory effect. Thus, plasmid pKH47, containing the poly(dA)poly(dT) region most proximal to the origin of pBR322 replication, was most severely affected.     

Nuclear proteins from Drosophila melanogaster embryos which specifically bind to simple homopolymeric sequences poly [(dT-dG).(dC-dA)]

The binding of nuclear proteins from Drosophila melanogaster embryos to simple homopolymeric DNA sequences was studied. Nuclear proteins were electrophoresed, transferred onto nitrocellulose and incubated with labelled synthetic homopolymers or natural fragment containing simple sequences. Several protein bands were found in the 65-72 KDa region, which specifically bind both poly [(dG-dT).(dA-dC)] and a natural fragment containing 40 bp of this sequence. These proteins do not bind to homopolymers poly [(dA).(dT)] and poly [(dG-dA).(dC-dT)], or other foreign DNAs.     

A unique deletion in pBR322 DNA caused by insertion of poly(dA).poly(dT)

A unique deletion covering around 43% of the pBR322 genome was found after attempting to insert 100 or 200 bp poly(dA).poly(dT) into the EcoRV site of pBR322 DNA. This result was not observed if an equivalent size heterologous DNA or a larger poly(dA).poly(dT) fragment of 10-20,000 bp was introduced at the same site. DNA sequencing analysis at the junctions suggests that a specific intramolecular pairing may be involved in the formation of this deletion mutant.