gene x ppt(gene10 基因十)--chapter-文庫吧
2025-01-04 07:49 本頁面
【正文】 pe. Organization of Interrupted Genes May Be Conserved ? Introns can be detected when genes are pared with their RNA transcription products by either restriction mapping, electron microscopy, or sequencing. ? cDNA – A singlestranded DNA plementary to an RNA, synthesized from it by reverse transcription in vitro. FIGURE 03: Comparison of the restriction maps of cDNA and genomic DNA for mouse βglobin Organization of Interrupted Genes May Be Conserved ? The positions of introns are usually conserved when homologous genes are pared between different anisms. – The lengths of the corresponding introns may vary greatly, though. ? Introns usually do not encode proteins. FIGURE 05: Mammalian genes for DHFR have the same relative anization of short exons and long introns, but vary in the lengths of introns Exon Sequences under Negative Selection Are Conserved but Introns Vary ? Comparisons of related genes in different species show that the sequences of the corresponding exons are usually conserved, but the sequences of the introns much less so, when the exons are under selective pressure to retain the capacity to encode useful proteins. FIGURE 06: Related genes diverge in the introns Data provided by Philip Leder, Harvard Medical School Exon Sequences under Positive Selection Vary but Introns Are Conserved ? Under positive selection an individual with an advantageous mutation is able to produce more progeny than others without the mutation. ? Due to intrinsic genomic pressures, such as that which conserves the potential to ext
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