From Gene to Protein A.P. Biology
What do genes code for? How does DNA code for cells & bodies? DNA cells and bodies are made from the instructions in DNA DNA proteins cells bodies 2
transcription and translation The “Central Dogma” Flow of genetic information in a cell How do we move information from DNA to proteins? transcription translation DNA RNA protein trait To get from the chemical language of DNA to the chemical language of proteins requires 2 major stages: transcription and translation DNA gets all the glory, but proteins do all the work! replication 3
RNA Contains ribose instead of deoxyribose Single stranded Nucleotide uracil replaces thymine
DNA and RNA RNA DNA Nucleotide (monomer) Single Stranded Sugar, Phosphate Group & Nitrogenous Base (A T C G) A with T; C with G Sugar- Pentose Deoxyribose Double Stranded Anti-parallel Complementary (One can be a template for another strand) Single Stranded Nucleotide (monomer) Sugar, Phosphate Group & Nitrogenous Base (A U C G) A with U; C with G Sugar- Pentose Ribose sugar 3 types of RNA
3 Types of RNA Messenger RNA = mRNA -Carries DNA sequence from the nucleus to the ribosome Ribosomal RNA = rRNA -Component of ribosome Transfer RNA = tRNA -Carries amino acid (anticodon) to the codon on mRNA sequence
Basic Principles of Transcription and Translation Transcription (takes place in nucleus) Is the synthesis of RNA under the direction of DNA Produces messenger RNA (mRNA) Translation (takes place outside the nucleus) Is the actual synthesis of a polypeptide, which occurs under the direction of mRNA Occurs on ribosomes
In prokaryotes Transcription and translation occur together Prokaryotic cell. In a cell lacking a nucleus, mRNA produced by transcription is immediately translated without additional processing. (a) TRANSLATION TRANSCRIPTION DNA mRNA Ribosome Polypeptide
In eukaryotes RNA transcripts are modified before becoming true mRNA Figure 17.3b Eukaryotic cell. The nucleus provides a separate compartment for transcription. The original RNA transcript, called pre-mRNA, is processed in various ways before leaving the nucleus as mRNA. (b) TRANSCRIPTION RNA PROCESSING TRANSLATION mRNA DNA Pre-mRNA Polypeptide Ribosome Nuclear envelope