A PowerPoint presentation by Gene Tempest From Gene To Protein A PowerPoint presentation by Gene Tempest

Table of Contents Overview Transcription RNA Processing Translation Differences in protein Synthesis Between Prokaryotes and Eukaryotes Point Mutations Bibliography

Overview DNA RNA Protein The one gene-one polypeptide hypothesis Main processes in protein production in eukaryotes: 1. Transcription 2. RNA processing 3. Translation The synthesis of RNA under the direction of DNA Yields the finished mRNA Actual synthesis of a polypeptide, under the direction of mRNA DNA RNA Protein

Animation 17.1

Terms Triplet Code Template Strand Codon Initiation Codon Termination Codons Series of three-nucleotide “words” that contain the instructions for making polypeptide chains. The one out of the two DNA strands that is transcribed. mRNA base triplet AUG (also codes for amino acid methionine) UAA UAG UGA

Fig. 17.3

Fig. 17.4 Note: Based on mRNA Codon

Pries the two strands of DNA apart and hooks together the RNA nucleotides, as they base-pare along the DNA template Transcription In eukaryotes, a collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription A closer look Stretch of DNA that is transcribed into an RNA molecule Terms RNA polymerase Transcription unit Promoter Transcription factors Terminator RNA sequence that functions as the actual termination signal Region of DNA where RNA polymerase attaches and initiates transcription

Stages 1. RNA polymerase unwinds the two DNA strands. RNA synthesis begins at the starting point on the template strand. 2. The RNA polymerase works its way “downstream”. 5’ 3’ 3. RNA polymerase transcribes a terminator. RNA is released. RNA polymerase dissociates from DNA

Fig. 17.6

Animation 17.2

The removal of a large portion of the originally synthesized RNA molecule RNA Processing A closer look Non-coding segments of nucleic acid that lie between coding regions Terms Small nuclear ribonucleoproteins; joins with proteins to form the spliceosome RNA splicing Introns Exons snRNPs Spliceosome Cuts at specific points to release the intron, then joins the two exons together Eventually expressed--or translated into amino acid sequences

Stages 1. The ends of each pre-mRNA molecule are modified: - the 5’ end is capped off with a modified form of a guanine (G) nucleotide ( 5’ cap ) - a poly(A) tail, consisting of adenine nucleotides, attaches to the 3’ end 2. The spliceosome removes the introns and produces joined exons, now mRNA

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Translation Terms Transfer RNA Function: to transfer amino acids from the cytoplasm to a ribosome Holds the tRNA carrying the growing polypeptide chain A closer look Relaxation of the base-paring rules Terms tRNA Wobble rRNA P Site A Site E Site Sites on the large ribosomal subunit Ribosomal RNA Function: structural and catalytic role in ribosomes Holds the tRNA carrying the next amino acid to be added to the chain Exit for discarded tRNAs

Stages I. Initiation 1. Small ribosomal subunit binds to a molecule of mRNA 2. A large ribosomal subunit complex completes it II. Elongation 1. Codon Recognition 2. Peptide bond formation 3. Translocation III. Termination 1. The ribosome accepts a release factor instead of tRNA 2. The release factor hydrolyses the bond between tRNA and P site 3. Ribosomal subunits dissociate

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Differences between Prokaryotes and Eukaryotes Can simultaneously transcribe and translate the same gene Newly made proteins can diffuse to their sites of function Nuclear envelope segregates transcription from translation Have complicated mechanisms for targeting proteins to their appropriate destinations

Point Mutations Vocabulary Chemical changes in just one or a few base pairs in a single gene Substitutions Insertions and deletions Replacement of one nucleotide and its partner in the complementary DNA strand with another pair of nucleotides Vocabulary Missense Mutation Nonsense Mutation Frameshift Mutation The altered codon still codes for an amino acid Addition or loss of one or more nucleotide pairs in a gene Alterations that change amino acids to a stop signal Alters the reading frame of the genetic message

Bibliography Campbell, Mitchell, Reece. “Biology Fifth Edition”. Illinois, USA. 1999 Biology Fifth Edition CD-ROM http://www.animationfactory.com http://occawlonline.pearsoned.com/bookbind/pubbooks/campbell_awl/chapter17/deluxe.html