Question

can you guys please give me the correct answers and explain why?

12. Which of the following statements concerning histones is INCORRECT? A. The N-terminal tails of histone proteins are frequently post-translationally modified B. Histones are small, basic proteins. C. Histones bind DNA via hydrogen bonding with bases in the major groove. D. Histone HI is not one of the core histones. E. Histones are present in eukaryotes but not bacteria. V 13. You are studying two E coli genes You know that they both are constitutive" or expressed at a constant level. This means that they are not regulated by any auxiliary proteins. You also know that the two genes are transcribed by Sigma 70 - RNA Polymerase. However, gene A is transcribed at a much higher level than gene B. What is the simplest explanation for this difference? A. Gene B is transcribed 3 to 5 B. The two genes are on opposite strands of the chyomosome C. The gene B transcript is terminated by Rho D. The-10-35 sequence for gene A is closer to consensus E. The gene A ORF starts with an AUG 14. In the replisome, Helicase: A Contacts primase and stimulates its activity. B. Is loaded at oriC by the Clamp Loader. C. Travels on the leading strand template. D. Moves in a 3-5' direction. E. Is a Type II topoisomerase 15. Which of the following statements regarding RNA structure is INCORRECT? A. RNA structure is not constrained to the shape of the helix B, RNA can contain G:U base pairs C/RNA can contain three bases hydrogen bonded together D. The 2'hydroxyl in RNA makes it especially stable at high pH E. RNAs contain post-transcriptionally modified bases

Answer 1

12. Incorrect: C. Histones bind DNA via hydrogen bonding with bases in the major groove. (Histone actually interacts with DNA via ionic interaction between positively charged bases in histone and negatively charged phosphate backbone in DNA. Option A is correct and N terminal tail of histones are most often modified. The rest of the options are corecor.)

13. Answer: C. The gene B transcript is terminated by Rho. (If this happens then gene B will be transcribed less than gene A. Option A is wrong as all genes are transcribed 5' to 3'. Option B is wrong as the given information doesn't really imply it. Option D is wrong as both their 10-35 sequence has to be closer to consensus in order to have constitutive expression. Option E is wrong as all gene's ORFs start with an AUG codon.)

14. Correct: A. Contacts primase and stimulates its activity (clamp loader loads DNA polymerase, helicase travels on both strands, moves in 5' to 3' direction, helicase and topoisomerase are different enzymes)

15. Incorrect: D. The 2' hydroxyl makes it especially stable at high pH. (RNA is not at all stable in high pH and degrades very easily in basic conditions. The other statements are all correct.)