eLa 5.1 Genetic Code Flashcards
How many nucleotides are in a codon?
3… If you missed this, drop out of medical school
What is DNA transcribed into?
mRNA
What molecules are involved in linking a codon sequence with its correct AA? What cellular component orchestrates this process?
tRNA, ribosome
What is the difference b/t ambiguity and degeneracy? Which is used to describe the genetic code?
Ambiguity would refer to codons coding for multiple AA. Degeneracy indicates that AA’s can have multiple codons.
Degeneracy
Where is the wobble position in the codon?
3rd position
How is it possible that there are 61 codons but only 48 different tRNA’s?
Some tRNA’s can recognize multiple codons, due to “wobbling.” This means that these tRNA’s don’t follow standard Watson-Crick rules
What are the three stop codons?
UAA, UAG, UGA
95% of proteins begin with which AA? What is its codon?
Methionine, AUG
What is a reading frame? mRNA molecules that code for a protein are often referred to as what type of frame?
Series of 3 nucleotide codons that must be read in order to produce a protein.
Open Reading Frame (ORF)
What is a frameshift mutation?
An insertion or loss of nucleotides in an ORF, that is not a multiple of 3
What is a missense mutation?
Single nucleotide substitution (point) in a codon that results in the incorrect AA being incorporated into a protein. This can be deleterious or enhancing
What is a nonsense mutation?
Creation of a premature stop codon by changing one or more nucleotides
What is a silent mutation?
A mutation that doesn’t result in a change in AA. Mutation often occurs in the wobble position of the codon.
What is a SNP? Non-synonymous vs. synonymous?
Single nucleotide polymorphism.
non-synonymous: change AA
synonymous: no change in AA
How many AA’s have been observed in natural proteins? How can these be derived from the 22 original AA?
Over 140 AA’s. These are a result of post-tln modifications
