基因簇和基因重復ppt課件-在線瀏覽
2025-06-15 23:18本頁面
【正文】 ion, but they can be recognized by sequence similarities with existing functional genes. They arise by the accumulation of mutations in functional genes. Unequal crossingover rearranges gene clusters Figure Gene number can be changed by unequal crossingover. If gene 1 of one chromosome pairs with gene 2 of the other chromosome, the other gene copies are excluded from pairing. Rebination between the mispaired genes produces one chromosome with a single copy of the gene and one chromosome with three copies of the gene. Unequal crossingover rearranges gene clusters Thalassemia地中海貧血 is disease of red blood cells resulting from lack of either α or β globin. Figure Thalassemias result from various deletions in the αglobin gene cluster. Ribosomal RNA is the predominant product of transcription, constituting some 8090% of the total mass of cellular RNA in both eukaryotes and prokaryotes. The number of major rRNA genes varies from 7 in E. coli, 100200 in lower eukaryotes, to several hundred in higher eukaryotes. In bacteria, the multiple rRNA gene pairs are dispersed. In most eukaryotic nuclei, the rRNA genes are contained in a tandem cluster or clusters. Sometimes these regions are called rDNA. Genes for rRNA form tandem repeats Figure A tandem gene cluster has an alternation of transcription unit and nontranscribed spacer and generates a circular restriction map. Genes for rRNA form tandem repeats The pair of major rRNAs is transcribed as a single precursor in both bacteria and eukaryotic nuclei. Following transcription, the precursor is cleaved to release the individual rRNA molecules. Figure Transcription of rDNA clusters generates a series of matrices, each cor
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