L05 Translation Flashcards
________________ received a nobel prize for deciphering the genetic code.
A. Wilhelm Johannsen B. Johann Mischer C. Marshall Nirenburg D. Frederick Griffith E. Oswald Avery F. Chase and Hershey G. Erwin Chargaff H. Meselson and Stahl G. Kornberg
C. Marshall Nirenburg
Review:
Wilhelm Johannes - coined the term “gene”
Friedrich Miescher - isolated “nuclein” from salmon sperm (now known as nucleic acid)
Griffith discovered a “transforming factor” using rough and smooth strains of Pneumococcus
Avery reasoned DNA was transforming factor from treatment of virulent/non-virulant bacteria with deoxyribonuclease
Chase and Hershey used bacteriophages to reason that DNA is the genetic material
Charges quantified nucleotides (A,T,G,C)
Meseleson and Stahl produced evidence that DNA replicates in a semi-servative fashion
Kornberg received a nobel prize for his research studying the enzyme responsible for DNA replication
Why is the genetic code considered degenerate?
Because the code is redundant. With the exception of AUG (methionine) and UGG (tryptophan), more than one codon occurs for each amino acid.
The code is unambiguous meaning each code codes for one amino acid.
Chemical changes in just one base pair of a gene is called?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
F. Point mutations
In a point mutation, one nucleotide is swapped out for another. Therefore, the mutation occurs at a single point or location within the DNA strand. Point mutations usually only affect the codon that contains the altered nucleotide. Frameshift mutations are due to either insertions or deletions of nucleotides.
Which replaces one nucleotide and its partner with another pair of nucleotides?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
B. Nucleotide-pair substitution
Which has no effect on the amino acid produced by a codon because of redundancy in the genetic code?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
C. Silent mutations
Which change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
E. Nonsense mutations
Which still code for an amino acid, but not the correct amino acid?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
D. Missense mutations
What mutation is responsible for sickle-cell disease?
Point mutation
The wild type hemoglobin sequence is changed from CTT to CAT which transcribes GUA mRNA instead of GAA mRNA. The normal hemoglobin is translated from Glu and sickle-cell disease is translated from VAL.
Which may alter the reading frame due to an insertion or deletion of nucleotides?
A. Frameshift mutations B. Nucleotide-pair substitution C. Silent mutations D. Missense mutations E. Nonsense mutations F. Point mutations
A. Frameshift mutations
What is on each end of the tRNA?
Each carries a specific amino acid on one end
Each has an anticodon on the other end
the anticodon base-pairs with a complementary codon on mRNA
Describe base-pairing wobble and why is it used?
Wobble is a property that allows an identical tRNA to bind to different codons at the third base. It allows some tRNAs to bind to more than one codon.
It’s important because sometimes cells do not carry tRNAs for all codons.
Which site holds the tRNA that carries the growing polypeptide chain?
P site
Which site is the exit site, where discharged tRNAs leave the ribosome?
E site
Which site holds the tRNA that carries the next amino acid to be added to the chain?
A site
what are the 3 initiation steps of translations and what are the components that are brought together?
The initiation stage of translation brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits.
1) First, a small ribosomal subunit binds with mRNA and a special initiator tRNA
2) Then the small subunit moves along the mRNA until it reaches the start codon (AUG)
3) Proteins called initiation factors bring in the large subunit that completes the translation initiation complex
