Expression of genetic information

Expression of genetic information - C H A P T E R 5...

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40 C H A P T E R 5 EXPRESSION OF GENETIC INFORMATION Information Metabolism Directions and Conventions DNA Replication Types of DNA Polymerase Recombination Regulation of Information Metabolism Transcription Regulation of Transcription Translation Use of High-Energy Phosphate Bonds During Translation Information metabolism provides a way to store and retrieve the infor- mation that guides the development of cellular structure, communication, and regulation. Like other metabolic pathways, this process is highly reg- ulated. Information is stored by the process of DNA replication and meiosis, in which we form our germ-line cells. These processes are lim- ited to specific portions of the cell cycle. Information is retrieved by the transcription of DNA into RNA and the ultimate translation of the sig- nals in the mRNA into protein. INFORMATION METABOLISM DNA R RNA R protein R structure.
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Regulation of information metabolism occurs at each stage. The net result is that specific proteins can be made when their activities are needed. DNA is a double-stranded molecule in which the structure of the sec- ond strand can be deduced from the structure of the first strand. The sec- ond strand is complementary (A’s in the first strand match T’s in the DIRECTIONS AND CONVENTIONS The 5 9 end of the top (sense) strand is on the left. Top strand 5 RNA sequence. Decoded RNA sequence in 5 9 to 3 9 direction gives protein sequence in N to C direction (Fig. 5-1). 5 Expression of Genetic Information 41 RNA polymerase upstream sense strand downstream DNA 5 -ATG-TCC-GCA-CGG-CCT- 3 5 -AUG-UCC-GCA-CGG-CCU- 3 3 -TAC-AGG-CGT-GCC-GGA- 5 antisense (template) strand transcription translation RNA PROTEIN amino terminus carboxyl terminus NH 3 -Met-Ser-Ala-Arg-Pro-CO 2 + Figure 5-1 DIRECTIONALITIES in the flow of information from DNA to RNA to pro- tein. All new DNA or RNA chains grow by adding new nucleotides to a free 3 9 end so that the chain lengthens in the 5 9 to 3 9 direction. Protein is made by read- ing the RNA template starting at the 5 9 end and making the protein from the N to the C terminus.
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second and G’s match C’s) and runs in the opposite direction. This means that you don’t have to write both strands to specify the structure—one will do. When you see a sequence written with only one strand shown, the 5 9 end is written on the left. Usually this sequence is also identical to that of the RNA that would be made from this piece of DNA when tran- scribed left to right. The DNA strand that has the same sequence (except U for T) as the RNA that is made from it is called the sense strand . The sense strand has the same sequence as the mRNA. The antisense strand serves as the template for RNA polymerase.
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Expression of genetic information - C H A P T E R 5...

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