Question

13. Why are ribonucleoside triphosphates the monomers required for RNA synthesis rather than ribonucleoside monophosphates? A. Only ribonucleoside triphosphates contain the sugar ribose. B. Ribonucleoside triphosphates have low potential energy, making the polymerization reaction endergonic. C. Ribonucleoside triphosphates have high potential energy, making the polymerization reaction exergonic. D. Ribonucleoside monophosphates cannot form complementary base pairs with the DNA template. E. Ribonucleoside triphosphates are not used, rather all use deoxyriboside triphosphates. 14. How is a mutation in a bacterial cell that deletes three base pairs 10 base pairs upstream from the +1 site likely to affect transcription and why? A. A three-base-pair deletion is too small to have an effect. B. Termination will not occur because hairpin secondary structure cannot form C. The protein that is formed have one fewer amino acid than the normal protein D. Initiation will be inhibited because RNA polymerase core enzyme cannot bind to the promoter. E. Initiation will be inhibited because sigma cannot bind to the promoter. 15. A promoter is A. A protein that binds to the RNA polymerase to facilitate transcription B. A protein that binds to the ribosome to facilitate translation C. A sequence of nucleotides in the mRNA that facilitates binding to the ribosome D. A sequence in DNA that brings RNA polymerase near the site for transcription E. A section of DNA that can be thousands of base pairs away from the beginning of the gene and enhances transcription 16. What would happen if a mutation occurred in E coli that eliminated the production of the protein sigma? A. ribosomes would no longer be able to participate in translation B. mRNA transcripts would no longer be produced c. amino acids could no longer be connected to one another via peptide bonds D. introns would no longer be spliced out of mRNAs E. mRNA transcripts could not dissociate from the RNA polymerase 17. Which of the following mutations is most likely to cause a phenotypic change? A. a single nucleotide deletion in an exon coding for an active site B. a large inversion whose ends are each in the same region between genes C. a duplication of all or most introns D. a frameshift mutation one codon away from the 3' end of the nontemplate strand E. all of the above

Answer 1

13. Option c is correct answer

Why are ribonucleoside triphosphates the monomers required for RNA synthesis rather than ribonucleoside monophosphates.

Ribonucleoside triphosphates have high potential energy, making the polymerization reaction exergonic. DNA is transcribed to give RNA a copy.

Ribonucleoside triphosphates have high potential energy, making the polymerization reaction exergonic.

Because ribonucleoside triphosphates have three negatively charged phosphates close together, they have high potential energy, which is released during polymerization, making RNA synthesis spontaneous (ΔG<0) in cells.

14. option e is the correct answer

How is a mutation in a bacterial cell that deletes three base pairs 10 base pairs upstream from the +1 site likely to affect transcription and why

Initiation will be affected because sigma factor cannot bind to promoter

The +1 site is the transcription start site and the region 10 base pairs upstream is a region of the promoter critical for sigma binding and initiation.
Initiation will be inhibited because sigma cannot bind to the promoter.

15. Option d is the correct answer

Promoter sequences are DNA sequences the region in the gene where the RNA polymerase will bind and initiate the process of transcription.

16. Option b is correct answer

sigma factor (σ factor) (specificity factor) is a protein needed for initiation of transcription in bacteria. It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase (RNAP) to gene promoters.

17. Option a is correct answer

Which of the following mutations is most likely to cause a phenotypic change?

Da single nucleotide deletion in an exon coding for an active site