分子生物学()培训教案.pptVIP

interrupted gene(splitting gene): The actual genes are interrupted with non-coding DNA； Exon: the regions of the DNA that contain coding information, which make up of mature成熟的 mRNA; Intron: intervening介于其间的 sequences between the coding sequences, they will also be transcribe, but will be removed to yield the mature mRNA. 2.2.2.3 Eukaryotic genomes contain both nonrepetitive and repetitive DNA sequences Nonrepetitive A、Genes are generally coded by sequences in nonrepetitive DNA； B、the slowest fraction部分 in reassociation； C、Lower eukaryotes 10-20% higher plants (flowing plants) 80% higher animals (mammals) 50% repetitive sequence repetitive DNA Slightly repetitive sequence Moderately repetitive sequence Highly repetitive sequence Reassociation kinetics动力学 Slightly repetitive sequence copies：2~10 B. including : Yeast酵母 tRNA gene moderately repetitive sequence A、size：0.1~1kb(less than 10kb) B、copies：10~10000 C、including gene cluster群 and many transposon转座子(sometimes viewed as selfish DNA) D、functions：do not transcribe, maybe play some role in gene expression Tandem gene clusters簇：fixed repeat unit follow each other directly, occur as clusters at special site of chromosomes. These are genes whose products are required in unusually large quantities, such as 45S rDNA in African clawed frog(Xenopus laevis) has about 5000 tandem repeats, also is histone gene cluster rDNA gene cluster Sea urchin 450 copies Tobacco 750 copies Drosophila 100 copies Histone gene cluster H1 H4 H2B H3 H2A T 18s T 5.8s T 28s NT 18s T 5.8s T 45s 41s 20s 32s 28s 5.8s 18s Highly repetitive sequence A、typically 100 bp、thousands of copies、often organized as long tandem repeats； B、In some cases, the repetitive sequence has a base composition distinct from the genome average, which allows it to form a separate fraction by virtue of its distinct buoyant浮力 density. A fraction of this sort is called satellite DNA. C、mainly near the centromeres着丝粒 (in he