CH 11-13 worksheet Flashcards
If a polypeptide is made of 146 amino acids, what is the minimum number of nucleotides in the mRNA coding for this polypeptide?
Minimum number of nucleotides is 438
Each amino acid is coded by a codon consisting of three nucleotides.
What is the start codon in the provided nucleotide sequence?
AUG
AUG codes for Methionine and serves as the start codon in mRNA.
What would be the amino acid sequence synthesized from the nucleotide sequence 5’ AUG CG GA CA GG AU GC AG 3’?
Methionine - Arginine - Glycine - Serine
The sequence is translated using a codon chart.
How many isoaccepting tRNAs would you predict exist for the amino acid valine?
Multiple isoaccepting tRNAs exist for valine
Anticodons for valine include: 5’ GUU, 5’ GUC, 5’ GUA, 5’ GUG.
What is the anticodon for tryptophan?
5’ UGG 3’
Tryptophan is coded by the UGG codon.
What product would you get if you added a poly(C) mRNA in a cell-free system?
A polypeptide of repeating proline
Each C codon codes for proline.
During the translation of mRNAs, what does the start codon indicate?
Indicates an amino acid and the start of translation and sets the reading frame
The start codon is critical for initiating protein synthesis.
Which of the following is involved in the joining of a tRNA to its correct amino acid?
Aminoacyl-tRNA synthetases
These enzymes ensure the correct pairing of tRNAs with their respective amino acids.
During the elongation of a polypeptide, where does a free amino acid-tRNA enter?
A site on the ribosome
The A site is where new tRNAs enter during translation.
What are mutations?
Heritable changes in genetic information
Mutations can occur naturally or be induced by environmental factors.
Which of the following is not a type of mutation?
They are all types of mutations
Types of mutations include frameshift, missense, transition, and transversion.
What happens when three bases are inserted together in the middle of a gene?
Add 1 amino acid; No change in ORF; may or may not change the function of the protein
Insertion of three bases typically does not disrupt the reading frame.
What happens when three bases are deleted from the gene?
Remove 1 amino acid; No change in ORF; may or may not change the function of the protein
Deletion of three bases maintains the reading frame.
What is the effect of one base being inserted and another one deleted five bases downstream?
Change ORF for 5 bases; Some different amino acids in that region; may or may not change the function of the protein
This insertion and deletion can lead to a frameshift mutation.
Why do frameshift mutations frequently cause the translated protein to terminate downstream?
Changing the ORF can introduce an early stop codon (nonsense mutation)
Early stop codons can result in truncated proteins.
What cell type must be mutant for the next generation to be affected?
Germline cells
Mutations in somatic cells are not passed to offspring.
Why might some mutations not cause phenotypic changes?
Possible reasons:
* Mutation occurred in an intron
* Mutation was neutral or silent
* Genetic code is redundant
* Mutation could be conditional
Silent mutations do not change the amino acid sequence.
Why are mutations usually not visible in the F1 generation but visible in the F2?
If a mutation only occurs on 1 chromosome, the wildtype copy will express a dominant phenotype
Recessive mutations may not manifest until homozygous.
