Genome (redirected from Draft sequence)

genome: see genetics.

---

genome

all the genetic content contained within an organism. An organism's genome is made up of molecules of deoxyribonucleic acid (DNA) that form long strands that are tightly wound into chromosomes, which are found in the nucleus of eukaryotic organisms and in the cytoplasm of prokaryotic organisms. Chromosomes that are unique to certain organelles within a cell, such as mitochondria or chloroplasts, are also considered a part of an organism's genome. A genome includes all the coding regions (regions that are translated into molecules of protein) of DNA that form discrete genes, as well as all the noncoding stretches of DNA that are often found on the areas of chromosomes between genes. The sequence, structure, and chemical modifications of DNA not only provide the instructions needed to express the information held within the genome but also provide the genome with the capability to replicate, repair, package, and otherwise maintain itself. The human genome contains approximately 25,000 genes within its 3,000,000,000 base pairs of DNA, which form the 46 chromosomes found in a human cell. In contrast, Nanoarchaeum equitans, a parasitic prokaryote in the domain Archaea, has one of the smallest known genomes, consisting of 552 genes and 490,885 base pairs of DNA. The study of the structure, function, and inheritance of genomes is called genomics. Genomics is useful for identifying genes, determining gene function, and understanding the evolution of organisms.

---

genome, genom

1. the full complement of genetic material within an organism

2. all the genes comprising a haploid set of chromosomes

---

genome [′jē‚nōm]

(genetics)

The genetic endowment of a species.

The haploid set of chromosomes.

---

Genome 

a haploid chromosome set; the sum total of the genes localized in the individual set of chromosomes of a given organism. The term was introduced in 1920 by the German biologist H. Winkler. The genome is usually understood to mean the sum of the genes concentrated in the chromosomes, without taking into account the hereditary determinants connected with the structures of cytoplasm. In the gametes of diploid organisms, as well as in the cells of haploid organisms, there is one genome; in the somatic cells of diploid organisms there are two genomes. With an increase in ploidy of the cells, the number of genomes grows. In fertilization, the genomes of the paternal and maternal gametes unite. As a rule, genomes obtained from paternal and maternal gametes are homologous. Homology between all or some genomes exists in all but distant hybrids. Absolute homology of two genomes may be defined as the coinciding of the linear arrangement of the genes in every chromosome. This coinciding ensures the possibility of the normal conjugation of chromosomes in meiosis.

Changes in the number of chromosomes (for example, polyploidy or an increase or loss of individual chromosomes) are called genomic mutations. An organism in which one and the same genome is repeated several times is called au-topolyploid. An organism in which different genomes are combined is called allopolyploid. Wheats may serve as an example of the allopolyploids. The haploid number of chromosomes in hard wheat is 14, in soft wheat, 21; and in einkorn, seven. By hybridization and the study of the conjugation of chromosomes in meiosis, it was ascertained that in all wheats there is one common genome (genome A) made up of seven chromosomes. In hard and soft wheat there are two common genomes (genomes A, B), each having seven chromosomes. Finally, in soft wheat, there is still another special genome (genome D), also made up of seven chromosomes. Thus, the genomic formula for einkorn is AA and for hard wheat it is AABB. Soft wheat, which has arisen in the process of evolution by the crossing of three different wild cereals and by the doubling of the number of chromosomes in the hybrids, has the genomic formula AABBDD.

In the experiments of the Soviet geneticist G. D. Kar-pechenko, radish and cabbage genomes were combined for the first time in a hybrid organism. By means of corresponding crossings and cytological analysis, the origin of separate genomes can be established. For example, V. A. Rybin obtained (resynthesized) a cultivated plum by crossing the cherry plum and the sloe; thus it was established that the genome of a plum includes cherry plum and sloe genomes. Of great significance in understanding the structure and functioning of the genome have been the establishment of the structure of the molecules of nucleic acids (DNA and RNA) and of the mechanisms of their replication, and the establishment of the means of “tracing” and transmitting genetic information.

V. N. SOIFER and V. V. KHVOSTOVA