Overview
This lecture explains how DNA leads to the creation of proteins through the processes of transcription and translation, highlighting the roles of RNA and codons in protein synthesis.
DNA and Traits
- DNA contains genes that code for proteins, which determine traits like eye color.
- Genes are sections of DNA that serve as instructions for protein production.
- Proteins perform essential roles in transport, structure, enzymes, and protection in the body.
Protein Synthesis Overview
- Protein synthesis is the process of making proteins from genetic instructions.
- There are two main steps: transcription and translation.
- Transcription occurs before translation.
Transcription
- Transcription happens in the nucleus, where DNA is used to create messenger RNA (mRNA).
- RNA polymerase is the enzyme that matches RNA bases to DNA bases.
- mRNA is a single-stranded molecule that carries the genetic message from DNA.
- mRNA may require editing before leaving the nucleus.
Translation
- mRNA exits the nucleus and attaches to a ribosome in the cytoplasm.
- Ribosomes, made of ribosomal RNA (rRNA), are the site of protein synthesis.
- Transfer RNA (tRNA) carries amino acids to the ribosome.
- tRNA reads mRNA codons (three-base sequences) with complementary anticodons.
- Each codon specifies a particular amino acid using a codon chart.
- AUG is the start codon, coding for methionine; some amino acids have multiple codons.
- Amino acids are linked together by peptide bonds to form a protein chain.
- Translation ends when a stop codon is reached, signaling the completion of the protein.
Key Terms & Definitions
- Gene — A segment of DNA that codes for a protein.
- Protein Synthesis — The process of making proteins from genetic information.
- Transcription — The process of copying DNA into mRNA in the nucleus.
- RNA Polymerase — Enzyme that synthesizes mRNA from a DNA template.
- mRNA (Messenger RNA) — RNA molecule that carries genetic information from DNA to ribosomes.
- rRNA (Ribosomal RNA) — RNA component of ribosomes.
- tRNA (Transfer RNA) — RNA that brings amino acids to the ribosome during translation.
- Codon — A sequence of three mRNA bases that codes for a specific amino acid.
- Anticodon — A set of three bases on tRNA that pairs with a codon on mRNA.
- Peptide Bond — Chemical bond that links amino acids together in a protein.
Action Items / Next Steps
- Review the process of mRNA editing.
- Practice using a codon chart to translate mRNA codons into amino acids.