Showing papers on "Genomics published in 1988"

Tomato genome is comprised largely of fast-evolving, low copy-number sequences

Abstract: Fifty random clones (350–2300 bp), derived from sheared, nuclear DNA, were studied via Southern analysis in order to make deductions about the organization and evolution of the tomato genome. Thirty-four of the clones were mapped genetically and determined to represent points on 11 of the 12 tomato chromosomes. Under moderate stringency conditions (≤80% homology required) 44% of the clones were classified as single copy. Under higher stringency, the majority of the clones (78%) behaved as single copy. Most of the remaining clones belonged to multicopy families containing 2–20 copies, while a few contained moderately or highly repeated sequences (10% at moderate stringency, 4% at high stringency). Divergence rates of sequences homologous to the 50 random genomic clones were compared with those corresponding to 20 previously described cDNA (coding sequence) clones. Rates were measured by probing each clone (random genomics and cDNAs) onto filters containing DNA from various species from the family Solanaceae (including potato, Datura, petunia and tobacco) as well as one species (watermelon) from another plant family, Cucurbitaceae. Under moderate stringency conditions, the majority of the random clones (single copy and repetitive) failed to detect homologous sequences in the more distantly related species, whereas approximately 90% of the 20 coding sequences analyzed could still be detected in all solanaceous species. The most highly repeated sequences appear to be the fastest evolving and homologous copies could be detected only in species most closely related to tomato. Dispersion of repetitive sequences, as opposed to tandem clustering, appears to be the rule for the tomato genome. None of the repetitive sequences discovered by this random sampling of the genome were tandemly arranged — a finding consistent with the notion that the tomato genome contains only a small fraction of satellite DNA. This study, along with a companion paper (Ganal et al. 1988), provides the first general sketch of the tomato genome at the molecular level and indicates that it is comprised largely of single copy sequences and these sequences, together with repetitive sequences are evolving at a rate faster than the coding portion of the genome. The small genome and paucity of highly repetitive DNA are favourable attributes with respect to the possibilities of conducting chromosome walking experiments in tomato and the fact that coding regions are well conserved among solanaceous species may be useful for distinguishing clones that contain coding regions from those that do not.

Genetics: A Molecular Approach

Abstract: Part 1 Genes and gene expression: the origins of genetic and molecular biology genes are made of DNA the structure of DNA gene and biological information transcription types of RNA molecule - rRNA and tRNA types of RNA molecule - mRNA the genetic code translation control of gene expression replication of DNA molecules alterations in the genetic material Part 2 Genomes: viruses - the simplest forms of life prokaryotic genomes eukaryotic genomes the human genome Part 3 Studying genes and genomes: what Mendel discovered using Mendelian genetics to study eukaryotic genes genetic analysis of bacteria cloning genes studying cloned genes studying genomes answers to selected problems

Human genome sequencing.

Abstract: The human genome contains 3 billion base pairs of DNA, sufficient to encode 100,000 to 300,000 genes. Since the number of genes that make up a human being is not known, this estimate is based upon a national average size for a mammalian gene. If the average gene is 30,000 bases long, there will be about 100,000 genes. Many of these genes will not be simple structures. More and more genes appear to have alternate ways of being read from the DNA, so that several different protein products can be made from a single gene. The total complexity of the human being then is about 100,000 to 500,000 processes.