How to produce a human with 3 chromosomes and 1000 primary genes

Interstitial colocalization of two cervid satellite DNAs involved in the genesis of the Indian muntjac karyotype

A number of repetitive DNA clones were generated from PCR amplifications of Indian muntjac genomic DNA using primer sequences derived from a white tailed deer satellite II DNA sequence. One clone (Mmv-0.7) was characterized and shown to be a cervid satellite II DNA clone. Multiple colored FISH studies with cervid satellite I (C5) and this satellite II clone (Mmv-0.7) to Chinese muntjac metaphase chromosomes localized both satellite DNAs at the pericentromeric regions of all chromosomes except for chromosome 3 and the Y chromosome, whereas chromosome 3 exhibited pericentromeric satellite II DNA only. Where distinguishable, the pericentromeric satellite II signals appeared terminally oriented with respect to satellite I. Six pairs of Chinese muntjac autosomes had interstitial satellite I sites with four of these autosomal pairs (chromosomes 1, 2 and two other smaller autosomal pairs) also exhibiting interstitial satellite II signals. An interstitial site on the X chromosome was found to have satellite II signals. For the Indian muntjac chromosomes, FISH studies revealed a pericentromeric hybridization for satellites I and II as well as 27 distinct interstitial hybridization sites, each having at least one of the satellite DNAs. These data were used to more precisely define the chromosome fusion-associated breakpoints that presumably led to the formation of the present-day Indian muntjac karyotype. It further hints at the possibility that the Indian muntjac karyotype may have evolved directly from a 2n = 70 ancestral karyotype rather than from an intermediate 2n = 46 Chinese muntjac-like karyotype.

The atomic basis of biological symmetry and periodicity

Geometric derivations and mathematical formulas have shown how the symmetrical patterns of plants, animals and crystals, follow similar mathematical solutions. These transformations have had the great value of indicating relationships between different types of patterns. However, they could neither shed light on the material processes that led to the emergence of symmetries in nature, nor explain their transfer to higher levels of organization, as evolution proceeded from simple molecular systems to complex living organisms. Several phenomena contribute to elucidate the material processes that have led to the emergence and transfer of symmetries. Their characteristics can be summarized: (1) symmetries are inherent to the structure of matter, since they already occur in the elementary particles, such as the neutrino; (2) simple atoms, such as oxygen and hydrogen produce a six-ray symmetry in water crystals a pattern from which these crystals cannot depart; (3) the mechanism of twinning, common in minerals, obliges several components to associate in a regular fashion guided by the properties of their atoms; (4) the symmetries of crystals are decided by the electronic properties of their constituent atoms. Since living organisms consist of the same atoms that are found in the minerals, it is not surprising that the symmetries of the minerals were transferred intact to the cell and organism levels; (5) another atomic property that has been preserved is periodicity. The existence of the Periodic Table of the elements shows how this phenomenon is so well established at the atomic level. This periodicity was also transferred to the living organism level. Both biological structures and functions display periodicity; (6) the recurrence of the same type of symmetry in minerals, plant organs and animal structures is an expression of the preservation of this periodicity; (7) another manifestation of the periodicity is found in the recurrence of the same symmetry in flowers of a large number of plant families which are not closely related in evolutionary terms; (8) the re-emergence of the same symmetry at different levels of organization is also elucidated by the fact that different atom combinations can display the same form and even the same function. This is what has been called molecular mimicry. Examples are the minerals with quite different chemical compositions which display the same symmetry and the proteins, that although they consist of different amino acid sequences, result in the same structural pattern and the same function. Due to the occurrence of molecular mimicry, in the cell's main macromolecules, an organism does not even need to have the same genes to exhibit a symmetry that appeared long ago in evolution; and (9) support for the concept that the biological periodicity is anchored on the chemical periodicity is found, among other features, on the fact that the six atoms that build the main macromolecules of the cell: the nucleic acids and proteins are all simple atoms that are located in a 'niche' on the right side of the Periodic Table of the chemical elements. The basis of biological symmetry and periodicity is now starting to be elucidated in atomic terms.

A tandemly repetitive, centromeric DNA sequence from the Canadian woodland caribou (Rangifer tarandus caribou): its conservation and evolution in several deer species

A highly repetitive DNA clone, designated Rt-Pst3, was isolated from the PstI digest of Canadian woodland caribou (Rangifer tarandus caribou; 2n = 70) genomic DNA. It was found to be a 991 bp monomer of a tandemly repeated DNA sequence comprising about 5.7% of the genome and localized to the centromeric regions of all caribou acrocentric autosomes. Southern blot analyses revealed that this caribou satellite DNA sequence was well conserved in the genomes of five other deer species studied. In situ hybridization studies revealed Rt-Pst3-homologous DNA sequences in the centromeric regions of white-tailed deer chromosomes and Asian muntjac chromosomes, as well as at several interstitial chromosome regions in Indian muntjac chromosomes. Comparisons of the Rt-Pst3 DNA sequence to previously identified centromeric satellite DNA fragments from three other deer species revealed considerable DNA sequence similarity. The first ca. 800 bp of the Rt-Pst3 clone was found to share 73.8% similarity to the CCsatI clone of the European roe deer, 64.7% sequence similarity to the C5 DNA clone of the Chinese muntjac, and 64.8% and 65.6% sequence similarity to the 1A and B1 clones of the Indian muntjac, respectively. Moreover, the last 191 bp of the Rt-Pst3 clone was found to share about 60% DNA sequence similarity to the first 191 bp of the same clone. Amplification of one original ca. 800 bp monomer unit, along with the first 191 bp of the following juxtaposed monomer unit could have resulted in the tandemly repeated, 991 bp monomer unit now seen in the caribou genome. It is postulated that the centromeric satellite DNA found in other deer species, having repeat lengths greater than 800 bp, could also have evolved in a similar manner from a more ancestral monomeric unit of ca. 800 bp.

DNA cloning and hybridization in deer species supporting the chromosome field theory

The Cervidae show the largest variation in chromosome number found within any mammalian family. The eight species of deer which are the subject of this study vary in chromosome number from 2n = 70 to 2n = 6. Three species of Bovidae are also included since they belong to a closely related family. Digestion of nuclear DNAs with the restriction endonucleases Hae III, Hpa II, Msp I, Eco RI, Xba I, Pst I and Bam HI reveals that there is a series of highly repetitive sequences forming similar band patterns in the different species. There are two bands (1100 and 550 base pairs) which are common to all species although the two families separated more than 40 million years ago. To obtain information on the degree of homology among these conserved sequences we isolated a Bam HI restriction fragment of approximately 770 base pairs from red deer DNA. This sequence was 32P labeled and hybridized by the Southern blot technique with DNAs cleaved with Bam HI, Eco RI, Hpa II and Msp I. Moreover, the same sequence was cloned in the plasmid vector pBR322 nick translated with 32P and hybridized with the DNAs of 8 species of Cervidae and 3 of Bovidae. The same cloned probe was labeled with 3H and hybridized in situ with the metaphase chromosomes of red deer (2n = 68) and Muntiacus muntjak (2n = 7 male). Homologies are still present between the highly repetitive sequences of the 8 species of Cervidae despite the drastic reorganization that led to extreme chromosome numbers. Moreover, the cloned DNA sequence was found to occupy the same position, in the proximal regions of the arms, in both red deer (2n = 68) and M. muntjak (2n = 7 male) chromosomes. The ribosomal RNA genes and the centromeres in these species have also maintained their main territory despite the drastic chromosome reorganization. These results are experimental confirmation of the chromosome field theory which predicted that each DNA sequence has an optimal territory within the centromere-telomere field and tends to occupy this same territory following chromosome reorganization.

Isozyme studies in provenance research of forest trees

The nature and origin of the isozymes and the techniques for their detection in forest trees are briefly reviewed. The theories used to interpret the isozyme variation are summarized. Recent isozyme variation studies in provenance research are discussed in relation to known variation pattern detected by classical nursery and field tests. The populations of a tree species can be sometimes, but not always, distinguished by their isozyme patterns. For a number of species, relationships between environment of origin of the provenances and some isozyme frequencies have been statistically established. In one case (Picea sitchensis) where direct comparison between the variation pattern detected by isozymes and the genetic variation of silviculturally important traits was possible, no meaningful relationships between both patterns could be detected. Nei's genetic distances and indices of gene diversity do not appear to be useful in provenance research. The concept of genetic distance based on gene frequencies is probably not very useful in provenance research either.

Conservation of repetitive DNA sequences in deer species studied by southern blot transfer

The Cervidae show one of the largest variations in chromosome number found within a mammalian family. The five species of the deer family which are the subject of this study vary in chromosome number from 2n = 70 to 2n = 6. Digestion with the restriction enzymes EcoRI, HpaII, HaeIII and MspI reveals that there is a series of highly repetitive sequences forming similar band patterns in the different species. To obtain information on the degree of homology among these conserved sequences we isolated a HpaII restriction fragment of approximately 990 base pairs from reindeer DNA. This DNA sequence was 32P-labelled and hybridized by the Southern blot technique to DNAs cleaved with HpaII and HaeIII from the reindeer and four other Cervidae species. Hybridization to specific restriction fragments was recorded in all species. The patterns of hybridization showed a higher degree of similarity between reindeer, elk and roe deer than between reindeer and the Asiatic species (fallow deer and muntjac). Homologies are still present between the highly repetitive sequences of the five species despite the drastic reorganization that led to a change in chromosome number from 6 to 70.

Eukaryotic genome: model considerations

The paper presents a new model of chromosome structure based on the assumption that multiple circular subunits of DNA exist. The essential difference with previously described models is the circular DNA unit forms a central chromosome axis. Chromosome configurations during various phases of the cell cycle depend on the various conformations of this central integrating unit. The described model can be generalized for all haploid set of eukaryotic nucleus. Some aspects of the chromosome structure and their functions have been discussed.