* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Indezine Template
Protein adsorption wikipedia , lookup
Transcription factor wikipedia , lookup
List of types of proteins wikipedia , lookup
Protein (nutrient) wikipedia , lookup
Peptide synthesis wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
RNA silencing wikipedia , lookup
Promoter (genetics) wikipedia , lookup
Non-coding DNA wikipedia , lookup
Bottromycin wikipedia , lookup
Polyadenylation wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Molecular evolution wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Biochemistry wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Non-coding RNA wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Gene expression wikipedia , lookup
Messenger RNA wikipedia , lookup
Expanded genetic code wikipedia , lookup
Forensic DNA Analysis Protein Synthesis Overview: The Flow of Genetic Information • The information content of DNA is in the form of specific sequences of nucleotides • The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins • Proteins are the links between genotype and phenotype • Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation The central dogma… • DNA RNA Protein • RNA is the intermediate between genes and the proteins for which they code • Transcription is the synthesis of RNA under the direction of DNA • Happens in the nucleus • Transcription produces messenger RNA (mRNA), carries DNA message to ribosome • Translation is the synthesis of a polypeptide, which occurs under the direction of mRNA • Ribosomes are the sites of translation Codons • There are 20 amino acids, but there are only four nucleotide bases in DNA • The flow of information from gene to protein is based on a triplet code: a series of non-overlapping, threenucleotide words • A triplet=1 codon=1 amino acid Overview • During transcription, one of the two DNA strands called the template strand provides a template for ordering the sequence of nucleotides in an RNA transcript • During translation, the mRNA base triplets, called codons, are read in the 5 to 3 direction • Each codon specifies the order of amino acids to make a protein • RNA bases: A, G, C, and Uracil instead of Thymine Transcription • The three stages of transcription: • Initiation • Promoters signal the initiation of RNA synthesis and transcription factors mediate the binding of RNA polymerase and the initiation of transcription • Elongation • RNA polymerase unwinds helix and adds RNA nucleotides to the 3’ end. DNA helix reforms after RNA Polymerase moves away • Termination • The polymerase falls off the DNA after the mRNA is formed mRNA processing • mRNA is ‘processed’ after transcription to prepare it for leaving the nucleus to travel to the ribosome. • It receives a 5’ cap and poly A tail to the 3’ end • Parts of the mRNA transcript are removed (spliced) 5 Exon Intron Exon Exon Intron 3 Pre-mRNA 5 Cap Poly-A tail 1 30 31 Coding segment mRNA 5 Cap 5 1 UTR 104 105 146 Introns cut out and exons spliced together Poly-A tail 146 3 UTR Translation • The three stages of translation: • Initiation • mRNA binds with the ribosome and moves along it until it reaches a start codon (AUG) • Elongation • tRNA (transfer) brings amino acids to the ribosome and adds them 1 by 1 based on the mRNA sequence • Termination • Codons (3-bases) are read and amino acids are added until the ribosome reaches a STOP codon (UGA, UAA, UAG) Fig. 17-18-4 Amino end of polypeptide E 3 mRNA Ribosome ready for next aminoacyl tRNA P A site site 5 GTP GDP E E P A P A GDP GTP E P A • http://www.youtub e.com/watch?v=5 bLEDd-PSTQ Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations • Mutations are changes in the genetic material of a cell or virus • Point mutations are chemical changes in just one base pair of a gene Types of Point Mutation • A base-pair substitution replaces one nucleotide with another pair • Silent mutations have no effect on the amino acid produced by a codon (codes for the same amino acid) • Missense mutations still code for an amino acid, but not the right amino acid • Nonsense mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein • Insertions and deletions are additions or losses of nucleotide pairs in a gene (changes the reading frame) Wild-type DNA template strand 3 5 5 3 mRNA 5 3 Protein Stop Amino end Carboxyl end A instead of G 3 5 Extra A 5 3 3 5 3 5 U instead of C 5 5 3 Extra U 3 Stop Stop Silent (no effect on amino acid sequence) Frameshift causing immediate nonsense (1 base-pair insertion) T instead of C missing 3 5 5 3 3 5 3 5 5 3 A instead of G missing 5 3 Stop Missense Frameshift causing extensive missense (1 base-pair deletion) missing A instead of T 5 3 3 5 U instead of A 5 5 3 3 5 missing 3 5 Stop Stop Nonsense (a) Base-pair substitution 3 No frameshift, but one amino acid missing (3 base-pair deletion) (b) Base-pair insertion or deletion