This week we learned about the central dogma! The central dogma a two-step process of transcription and translation. This is when information in genes flows into proteins.
DNA → RNA → protein.
Transcription is the synthesis of an RNA copy of a segment of DNA.
Translation is the process by which RNA is used to produce proteins.
Transcription has a three step process:
- In Initiation RNA Polymerase attaches to a “promoter” region in front of a gene. These “promoters” have characteristic DNA sequences.
- The “Template Strand” of DNA is the one that the RNA transcript is being produced off of (has an opposite sequence to the transcript)
- The “non template strand” of the DNA will have the same sequence as the RNA.
- Transcript production continues until the end of the transcription is reached
Translation also has a three step process:
- The mRNA attaches to the small ribosomal subunit and the ribosome assembles so that the start codon (AUG) is in the P-site.
- This is called the “translation initiation complex”
- The next code is then available in the A-site for the next incoming charged tRNA. The next codon determines the next two amino acid to be brought to the ribosome. The incoming charged tRNA enters at the A-site and the growing polypeptide is transferred to the new tRNA molecule.
- When a stop codon (UAG, UAA, or UGA) is encountered, a release factor binds to the A-site, and the polypeptide chain is released so the ribosome disassembles.
This video helps the summarize these two concepts that make up the central dogma:
We also briefly reviewed mutations:
- There are 2 major types of DNA- level mutations:
- Point mutations: one DNA base is replaced by another DNA base
- Frame-shift mutations: DNA bases are inserted or deleted (“in/dels”)
On Thursday we did a packet to learn about two different kinds of operons:
- inducible operons
- an operon naturally in the off position. This is only turned on by using a chemical signal called an inducer.
- repressible operons
- an operon that is naturally in the on position. This only turns off once enough production has occurred and a co-reppresor molecule signals the repressible operon to turn off.