Lecture Series 7

Lecture Series 7 - Gene Expression From DNA to Protein How cells read the genome Presentation01 Central Dogma of Molecular Biology Transcription is

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Unformatted text preview: Gene Expression From DNA to Protein: How cells read the genome. Presentation01 Central Dogma of Molecular Biology Transcription is the beginning of the process by which cells express their genetic information – their genes. Each gene can be transcribed and translated with a different efficiency, and this provides the cell with a way to make vast quantities of some proteins and tiny amounts of others. Furthermore, cells can change the expression of each gene dependent on its needs at the moment. The half-life of mRNA’s differs greatly depending on protein being produced. Requirements for Transcription A DNA template Appropriate ribonucleoside triphosphates – differs from replication Different sugar subunit Different base, Uracil (U) instead of thymine (T) The enzymes necessary to catalyze the process – RNA polymerases DNA Template Only one strand of the DNA helix is used as the template strand . Non-template strand can also be called the complementary strand or coding strand. DNA helix must be unwound for transcription to occur. Nucleotides NTP’s are the basic subunit for RNA and DNA NTP’s are composed of 3 components: Nitrogenous base Purine (ATP or GTP) Pyrimidines (UTP or CTP) Sugar that is ribose in RNA Phosphate group See chapter 2 for structure RNA is single-stranded. It can fold up into a variety of shapes. The ability to fold into these 3-d structures allows RNA to carry out functions in cells in addition to conveying information between DNA and protein. Transcription in Prokaryotes Transcription of DNA is carried out by RNA polymerase. Bacterial cells have a single kind of RNA polymerase that synthesizes all three major classes of RNA: mRNA, tRNA and rRNA. This enzyme unwinds the DNA helix, creates phosphodiester bond between nucleotides and proceeds in 5’ to 3’ direction. Does not require a primer. Is less reliable than DNA polymerase. This enzyme makes one mistake about every 10 4 nucleotides. mRNA is the nucleotide template used in translation to make proteins. tRNA (transfer RNA) is responsible to carry amino acids to the growing peptide chain in translation. rRNA (ribosomal RNA) combines with proteins to create ribosomes that are used to manufacture proteins. Transcription is the synthesis of RNA RNA synthesis can be divided into four stages: Binding of RNA polymerase to DNA Initiation of synthesis of chain of RNA Elongation of RNA chain Termination of RNA synthesis Binding of RNA Polymerase...
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This note was uploaded on 04/13/2008 for the course BIOL 308 taught by Professor Ragsdale during the Fall '07 term at Winona.

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Lecture Series 7 - Gene Expression From DNA to Protein How cells read the genome Presentation01 Central Dogma of Molecular Biology Transcription is

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