The Genetic Code Flashcards
According to the “Central Dogma”
- DNA needs to be translated into protein somehow
- Concern is that DNA is stuck in the nucleus
Solution to the “Central Dogma”
The message on DNA is copied first onto another molecule
Transcription
Process by which the codon base sequence on DNA is copied onto an mRNA molecule so that the code can be carried out into the cytoplasm
What is a codon?
- A sequence of 3 base pairs
- Codes for one amino acid
Translation
- Process by which codons on mRNA are converted into amino acids
- Eventually join together to make a protein
How many combinations of codons are there?
64
Why was the code said to be “Redundant” or “Degenerate”
Because there are 20 amino acids so several codons code for the same amino acid
Why is the code no longer called “Redundant” or “Degenerate”
Because this avoids issues when some types of substitution mutations occur
mRNA=
Messenger RNA
What is mRNA?
- Product of DNA transcription and is complementary to the DNA template
- Goes into the cytoplasm
- Binds to a ribosome
tRNA=
Transfer RNA
What is tRNA?
- Brings in amino acids to ribosomes according to the mRNA codons
- Folded up version of RNA
Parts of tRNA
- amino acid acceptor site
- mRNA binding site
What is an anticodon?
It is complementary to mRNA codes
rRNA=
Ribosomal RNA
What is rRNA?
- A two-part molecule that makes up ribosomes
What are the two parts of a ribosome?
- Heavy Subunit
- Light Subunit
RNA polymerase I
- Makes rRNA
- Made in nucleolus and shipped out
RNA Polymerase II
- Makes mRNA
- Made in nucleus and shipped out
RNA Polymerase III
- Makes tRNA
- Made in nucleus and shipped out
Prokaryotes…
- Have no nuclei
- DNA is not separate from ribosomes
- Transcription and translation occur quickly
Where does transcription occur in eukaryotes
- In the nucleus and mRNA must be modified before leaving it
Where does translation occur in eukaryotes?
- In the cytoplasm
- At the ribosomes
