1. Which feature of DNA structure most directly causes the need for Okazaki frag
ID: 217581 • Letter: 1
Question
1. Which feature of DNA structure most directly causes the need for Okazaki fragments?
A. Right-handed helix B. Complementary bases C. Antiparallel DNA strands D. Negatively-charged phosphates
2. DNA Gyrase (Topoisomerase):
A. Separates the two strands of the helix B. Stabilizes the open conformation C. Relaxes supercoiling D. Joins two DNA fragments together
3. DNA Helicase:
A. Separates the two strands of the helix B. Relaxes supercoiling C. Removes RNA primers D. Joins two DNA fragments together
4. Which enzyme does not form phosphodiester bonds?
A. DNA Ligase B. DNA Helicase C. DNA Polymerase I D. DNA Polymerase III
Explanation / Answer
1. C) anti parallel DNA strands
Okazaki fragments is formed because of the anti parallel nature of DNA. As a result of this anti parallel nature, the DNA could only be synthesised in the 3’ to 5’ direction. As a result, the leading strand would be synthesised in the 3’ to 5’ direction and the lagging strand is synthesised in the 5’ to 3’ direction.
2. C) Relaxes supercoiling
This is also referred to as the underwinding of the DNA that occurs against the right direction. This would be underwinding the helix or straightens the helix.
3. A. Separates the two strands of the helix
The enzyme DNA helicase would be used for separation of the double helix. These use the energy from the hydrolysis of ATP and also carry out removal of the association of nuclei acids for the recombination of homologous DNA.
4. B) DNA Helicase
DNA helicase breaks phosphodiester bonds and does not form phosphodiester bonds.
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