The Genetic Code
How many bases make up a codon?
3
What is a frameshift mutation?
A mutation caused by an insertion or deletion that shifts the reading frame, altering every codon downstream.
What is transcription?
The process of making an RNA copy of a DNA sequence.
How many amino acids does each transfer RNA carry?
One specific amino acid
What are changes that occur after translation called?
Post-Translational Modifications
What are the 3 types of RNA?
mRNA, tRNA, rRNA
What is a missense mutation?
A point mutation that changes one amino acid to another.
Where does transcription occur?
In the nucleus.
What is the function of tRNA?
It brings amino acids to the ribosome and matches them to the correct codons using its anticodon.
What are silent mutations?
Mutations that change a nucleotide but do not change the amino acid.
What is the function of mRNA?
It carries the genetic message from DNA in the nucleus to the ribosome for protein synthesis.
What is a nonsense mutation?
A point mutation that changes a codon into a stop codon, prematurely ending translation.
What acts as the template during transcription?
The DNA template strand.
What are the 3 stages of translation?
Initiation, elongation, termination
What is the difference between conservative and nonconservative mutations?
Conservative: amino acid is replaced with one of a similar type.
Nonconservative: amino acid is replaced with one of a different type, more likely altering protein function.
What are proteins made up of?
Amino acids
What is the difference between a sense codon and a nonsense codon?
Sense codons code for amino acids; nonsense codons are stop codons.
What does transcription produce?
An RNA molecule (Primary Transcript).
What is an anticodon?
A three-base sequence on tRNA that is complementary to a codon on mRNA.
What is the difference between hypomorphic, hypermorphic and amorphic mutations?
Hypomorphic: reduces gene function
Hypermorphic: increases gene function
Amorphic: completely eliminates gene function (null mutation)
Why do stop codons stop the process of translation?
They do not code for an amino acid. Instead, they cause the ribosome to detach and end translation.
What does the universality of the code indicate?
Almost all organisms use the same genetic code, suggesting a common evolutionary ancestor.
Why does transcription need to occur?
Because DNA cannot leave the nucleus, so a portable RNA copy is needed to get the message out to the rest of the cell.
Where does translation occur?
Ribosomes
What is an ectopic expression?
Expression of a gene in the wrong place or at the wrong time.