1. A graduate student studying a 350 base pair molecule of DNA found that 20% of
ID: 65104 • Letter: 1
Question
1. A graduate student studying a 350 base pair molecule of DNA found that 20% of these nucleotides were adenine. How many nucleotides were Guanine? Cytosine? Thymine? Uracil? Explain your answers.(3 pts)
2. Indicate how many equivalents of ATP (ATP, CTP, GTP etc.) are consumed and when they are consumed (e.g. step 4 of pyrimidine metabolism or converting CMP to CDP) in the formation of the following molecules. (12 pts; 2 pts each) You may use copy and paste in your explanations or simply refer to an earlier explanation to indicate when the ATP equivalents are used. a. IMP b. UMP c. GTP d. CTP e. dGTP f. dTTP 3. Cells utilize salvage pathways to rescue nitrogenous bases from degradation. In the APRT pathway adenine is salvaged to create a molecule of AMP. a. Indicate how many equivalents of ATP are conserved through this salvage pathway in the production of AMP; explain. (2 pts) In the HGPRT pathway hypoxanthine or guanine are rescued to form IMP or GMP. b. Indicate how many equivalents of ATP are conserved through the salvage of guanine in the production of GMP; explain. (1.5 pts) c. Indicate how many equivalents of ATP are conserved through the salvage of hypoxanthine in the production of GMP; explain. (1.5 pts)
4. When the helix axis of a closed circular duplex DNA of 3190 bp is constrained to lie in a plane, the DNA has a twist (T) of 290. When released, the B DNA takes up its normal twist. (5 pts; 2.5 pts each) a. Indicate the values of the linking number (L), writhing number (W), and the twist for both the constrained and the unconstrained conformational states of this DNA circle; show your work and explain your answer. b. Also indicate L, W and T for the unconstrained molecule if it is A DNA instead of B DNA; show your work and explain your answer. 5. Describe in detail how a gene of interest (GOI) can be expressed in E.coli using the methods below. Include all relevant steps that must be taken to ensure gene expression inside the host. (10 pts; 5 each) a. Using restriction enzymes b. Using topoisomerases (feel free to copy and paste relevant steps from part a and highlight the differences) 6. In lecture we discussed prokaryotic DNA replication. This replication is primarily done on circular DNA. Given the information you have, discuss how this process becomes problematic for long linear DNA molecules such as those found in Eukaryotic organisms. (5 pts)
Explanation / Answer
The DNA nucleotides otherwise called “bases” carry the message encoding for the synthesis of a protein. There are four such bases, namely, adenine (A), thymine (T), guanine (G), and cytosine (C), which are the building blocks of DNA’s double helical structure.
Among these base pairs, adenine binds with thymine and guanine binds with cytosine, this is called as complementary pairing. Both the strands of DNA are equal in length. Adenine and guanine are purines, thymine and cytosine are pyrimidines. So, purines pair with pyrimidines and vice versa.
It is given that, of the total 350 base pairs, 20% (70 bases) are adenine bases, means another 20% are thymine bases. Of the remaining 60%, 30% (105 bases) are guanine and another 30% are cytosine.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.