生物信息的传递.pptx

生物信息的传递;第2页/共129页;Content:;一、Some basic conception;1.Gene; 2.When a protein is needed by a cell, the genetic code for that protein must be read from the DNA and processed. A two step process: （1）Transcription = synthesis of a single-stranded RNA molecule using the DNA template (1 strand of DNA is transcribed). In Eukaryotes, transcription takes place in the nucleus. （2）Translation = conversion of a messenger RNA sequence into the amino acid sequence of a polypeptide (i.e., protein synthesis) Translation takes place on ribosomes in the cytosol, or on rough ER ;3. Template strand and nontemplate strand Template strand: The 3’ to 5’ strand of DNA in a coding region that serves as the template for RNA synthesis. The resulting RNA is a complement of the template strand.Nontemplate strand: The 5’ to 3’ strand of DNA in a coding region that has no function in producing the RNA. It has the same sequence as the initially transcribed RNA, except that Thymine in the DNA is Uracil in the RNA.;Sense/antisense +/- Nontranscribed/transcribed Nontemplate/template coding/template;5. Both strands encode genes; ;mRNA--(messenger) intermediate molecules used for transfer of information from DNA to protein. rRNA--(ribosomal) functional RNA molecules that are components of the ribosome. tRNA--(transfer) functional RNA molecules that serve as adapters in translation. snRNA--(small nuclear) functional RNA molecules that are involved in the removal of introns from pre-mRNAs. scRNA--(small cytoplasmic小胞浆RNA ) functional RNA molecules that are involved in protein traficking with the cytoplasm. i.e. scRNA参与蛋白质的合成和运输 ;8. How is an RNA strand synthesized? Regulated by gene regulatory elements within each gene. DNA unwinds next to a gene. RNA is transcribed 5’ to 3’ from the template (3’ to 5’). Similar to DNA synthesis, except: RNA polymerase No primer No proofreading NTPs instead of dNTPs (no deoxy-) Adds Uracil (U) instead of thymine (T) ;Unlike DNA replication, we will on