Transcription and Translation: From DNA to Protein, Slides of Biology

Download Transcription and Translation: From DNA to Protein and more Slides Biology in PDF only on Docsity! Transcription and Translation From DNA to RNA to protein Overview • Genes in DNA contain information to make proteins. • The cell makes mRNA copies of genes that are needed. • The mRNA is read at the ribosomes in the rough ER. • Protein is produced. Transcription RNA polymerase matches bases in the sense strand with RNA bases, building a strand of mRNA that carries the information encoded in the DNA. Transcription Encoded in DNA is a signal telling RNA polymerase where to stop. Transcription ends at that point. Transcription The completed mRNA molecule then moves from the nucleus to the rough ER for translation. Translation • The larger ribosomal subunit now binds to the smaller unit, forming a ribosomal complex. The tRNA binds to the first active site on the ribosome. Translation may now begin. Translation • The second codon in mRNA (GUU) matches the anticodon of a tRNA carrying the amino acid valine (CAA). The second tRNA binds to the second active site on the large subunit. Translation • A catalytic site on the larger subunit binds the two amino acids together using dehydration synthesis, forming a peptide bond between them. Translation • A new peptide bond forms between val and his on the catalytic site. The tRNA that carried val will detach and find another val in the cytoplasm. The mRNA strand will then shift over one more codon. Translation • The process continues until the ribosome finds a “stop” codon. The subunits detach from one another, the mRNA is released, and the polypeptide chain moves down the ER for further processing. The initial met is removed and the chain is folded into its final shape. Summary (a) DNA complementary DNA strand template DNA strand (b) mRNA (c) tRNA (d) protein Copyright © 2005 Pearson Prentice Hall, Inc. Types of Mutations • Point mutation: base substitution that may or may not code for a different amino acid. • Insertion mutation: one or more bases is inserted into the DNA strand. • Deletion: one or more bases is deleted from the DNA strand. Effects of mutations • Original: THE FAT CAT SAT • Point mutation: THA FAT CAT SAT • Insertion: THE FTT ATC ATS AT • Deletion: THE FTC ATS AT Hemoglobin mutations DNA mRNA Amino Acid Properties of AA Effect on protein Disease Original codon 6 CTC GAG Glutamic Acid Hydrophilic Normal None Mutation 1 CTT GAA Glutamic Acid Hydrophilic Neutral None Mutation 2 GTC CAG Glutamine Hydrophilic Neutral None Mutation 3 CAC GUG Valine Hydrophobic Loses water solubility Sickle Cell Anemia