DNA and Protein Synthesis
A particular triplet of bases in the template strand of DNA is 5'AGT 3'. The corresponding codon for the mRNA transcribed is 5' TCA 3' 3' ACU 5' either UCA or TCA, depending on the wobble in the first base 3'UCA 5' 3' UGA 5'
3'UCA 5'
Choose the answer that has these events of protein synthesis in the proper sequence. 1. An aminoacyl-tRNA binds to the A site 2. A peptide bond forms between the new amino acid and a polypeptide chain 3. tRNA leaves the P site, and the P site remains vacant 4. A small ribosome subunit binds with mRNA 5. tRNA translocates to the P site 4,1,3,2,5 5,4,3,2,1 1,3,2,4,5 2,4,5,1,3 4,1,2,5,3
4,1,2,5,3
What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids? The tertiary structure of the protein might be changed The biological activity or function of the protein might be altered The primary structure of the protein would be changed Only A and C are correct A, B or C are correct
A, B or C are correct
The nitrogenous base adenine is found in all members of which group? proteins, triglycerides, and testosterone proteins, carbohydrates and ATP alpha glucose, ATP and DNA ATP, RNA and DNA proteins, ATP and DNA
ATP, RNA and DNA
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which might this illustrate? The sequence is found in many but not all promoters The sequence is transcribed at the start of every gene The sequence evolves very rapidly Any mutation in the sequence is selected against The sequence does not mutate
Any mutation in the sequence is selected against
Which of the following BEST describes the flow of information in eukaryotic cells? RNA->DNA->proteins DNA->RNA->proteins DNA->proteins->RNA proteins->DNA->RNA RNA->proteins->DNA
DNA->RNA->proteins
Why might a point mutation in DNA make a difference in teh level of protein's activity? It might substitute the N terminus of the polypeptide for the C terminus It might exchange one serine codon for a different serine codon It might substitute an amino acid in the active site It might result in a chromosomal translocation It might exchange one stop codon for another stop codon
It might substitute an amino acid in the active site
Using RNA as a template for protein synthesis instead of translating proteins directly fro the DNA is advantageous for the cell because RNA is much more stable than DNA tRNA, rRNA and others are not transcribed RNA acts as an expendable copy of the genetic material only one mRNA molecule can be transcribed froma single gene, lowering the potential rate of gene expression mRNA molecules are subject to mutation but DNA is not
RNA acts as an expendable copy of the genetic material
In which of the following actions does RNA polymerase differ from DNA polymerase? RNA polymerase is much more accurate than DNA polymerase RNA polymerase binds to single-stranded DNA and DNA polymerase binds to a double-stranded DNA RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, wherease DNA polymerase must unwind the double helix before it can replicate the DNA RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
Which of the following statements best describes the termination of transcription in prokaryotes? Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome RNA polymerase transcribes through the polyadenation signal, causing proteins to associate with the transcript and cut it free from the polymerase RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. RNA polymerase transcribes through an intron, and the snRNP's cause the polymerase to let go of the transcript. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript
RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? The tRNA that was in the P site moves into the A site The tRNA that was in the A site departs from the ribosome via a tunnel The tRNA that was in the A site moves into the P site the polypeptide enters the E site The tRNA that was in the A site moves to the E site and is release
The tRNA that was in the A site moves into the P site
In the 1920s Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments, in teh 1940s, Charlotte Auerbach discovered that chemicals - she used nitrogen mustards - have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation? We want to make sure that it does not emit radiation We worry about its ability to cause infection We worry that it might cause mutation in cereal grain plants We want to be sure that it increases the rate of mutation sufficiently We want to prevent any increase in mutation frequency
We want to prevent any increase in mutation frequency
Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on teh polypeptide product? a deletion of a codon a substitution of the first nucleotide of a GGG codon a substitution of the third nucleotide in an ACC codon a deletion of 2 nucleotides an insertion of a codon
a deletion of 2 nucleotides
Which of the following nucleotide triplets best represents a codon? a sequence in tRNA at the 3' end a triplet separated spatially from other triplets a triplet at the opposite end of tRNA from the attachment site of the amino acid a triplet that has no corresponding amino acid a triplet in the same reading frame as an upstream AUG
a triplet in the same reading frame as an upstream AUG
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? separated ribosomal subunits with a polypeptide attached to the tRNA an assembled ribosome with a polypeptide attached to the tRNA in the P site an assembled ribosome with a separated polypeptide a cell with fewer ribosomes separated ribosomal subunits, a polypeptide, and free tRNA
an assembled ribosome with a polypeptide attached to the tRNA in the P site
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? separated ribosomal subunits, a polypeptide, and free tRNA separated ribosomal subunits with a polypeptide attached to the tRNA an assembled ribosome with a polypeptide attached to the tRNA in the P site an assembled ribosome with a separated polypeptide a cell with fewer ribosomes
an assembled ribosome with a polypeptide attached to the tRNA in the P site
A frameshift mutation could result from either an insertion or a deletion of a base a base deletion only a base insertion only deletion of three consecutive bases a base substitution only
either an insertion or a deletion of a base
What are the coding segments of a stretch of eukaryotic DNA called? replicons codons introns exons transposons
exons
Sickle cell disease is probably the result of which kind of mutation? both B and D frameshift point nonsense nondisjunction
point