Microbiology Procedure

Index >> Genes >> Number of Genes

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Genes All Cases of Genes are DNA Genes of Some Virus are RNA Genome and Plasmon Genes as a Unit of Recombination (Recon) Gene as a Unit of Mutation (Muton) Gene as a Unit of Function (Cistron) Numer of Genes Number of Nucleotides in Average Gene Duplication of Gene

Number of Genes

	Number of Genes The number of genes that an organism possesses has some relationship to its complexity. Viruses are parasitic on host cells. They produce messenger RNA but depend on the host cell for transfer RNA, ribosomal RNA and some enzymes. Consequently they require very few genes. The bacteriophages Rt7 and Qβ have RNA as their genetic material. The single stranded RNA contains only three genes
One codes for A protein the second for coat protein, and the third for one of four subunits of replicase. (The other three units of replicase are host proteins). Polyoma or SV40 viruses have 5-10 genes and their chromosomes are only 1.7 microns in length. The single stranded DNA virus ØX174 has DNA which codes for 9 Proteins. The bacterial virus lambda has about 40 genes and T4 has over a hundred genes. The number of genes in viruses ranges from only three in the simplest viruses to about 250 in the most complex ones. Although there is some relationship between the number of genes and the complexity of an organism there in no strict correlation between apparent genetic complexity and the DNA content per haploid nucleus.
Thus some fishes and amphibians contain 10 to 20 times more DNA than humans. Moreover, the size of the genome varies over a 20-fold range within the species of a phylum In Escherichia coli the chromosome is about 1 mm long and contains about 4,000 genes, and 4,000,000 base pairs. The total number of genes in Drosophila melanogaster is estimated to be 5,000 04 the basis of observation of bands in salivary gland chromosomes. The normal diploid human cell contains about S picograms (5 X 10-12) of DNA. This is equivalent to 5 X 109 (5 billion) base pairs. Assuming that the average gene contains 1,000 base pairs, the number of genes in the haploid human cell would be 5 X 106 (5 Million). This number is probably too high, at least by a factor of 10, because all DNA is not used for coding proteins

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Gene Regulation Loci and Alleles Split Genes Hexon Gene Ovalbumin Gene β-Globin Gene Genes Within Genes (Overlapping Genes)

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