Question

1. early in the process of dna replication, the enzyme ____ separates the two strands. o replicase o helicase o primase o endonuclease 3. dna polymerase __. o can work with both single - stranded and double - stranded dna o can add nucleotides in two different directions o requires a template for the synthesis of dna o fills in gaps in dna 4. if an organism lost the ability to make primase, what would it be unable to do? o add a short sequence of complementary rna to the existing dna strand o join okazaki fragments together o add a short sequence of complementary dna to the existing dna strand o supercoil dna after replication is complete 5. two different mechanisms for copying the dna strands are used because ____. o repressor proteins bind to one strand o the strands are oriented in opposite directions o purines abd pyrimadines require different enzymes o of changing levels of free nucleotides during the process

Explanation:

• Question 2: Helicase is the enzyme that unwinds and separates the two DNA strands during replication. Replcase is not a standard enzyme name in this context. Primase synthesizes RNA primers. Endonuclease cuts DNA strands internally.
• Question 3: DNA polymerase requires a template strand to synthesize a new complementary DNA strand. It works on single - stranded DNA (as it needs to read the template). It adds nucleotides in only one direction (usually \(5'\) to \(3'\)). Filling gaps in DNA is more of a role for DNA ligase in some repair or lagging strand synthesis (after Okazaki fragment processing).
• Question 4: Primase synthesizes short RNA primers. If an organism can't make primase, it can't add the short complementary RNA sequence to the existing DNA strand. Joining Okazaki fragments is done by DNA ligase. Adding a short DNA sequence (without a primer) is not how normal DNA replication (which requires a primer for DNA polymerase) works. Supercoiling is related to topoisomerase function.
• Question 5: The two DNA strands are oriented in opposite directions (\(5'\) to \(3'\) and \(3'\) to \(5'\)). DNA polymerase can only add nucleotides in the \(5'\) to \(3'\) direction. So, one strand (the leading strand) is synthesized continuously, and the other (the lagging strand) is synthesized as Okazaki fragments. Repressor proteins are more related to gene regulation. Purines and pyrimidines are incorporated by the same DNA polymerase (based on base - pairing rules). Changing levels of free nucleotides do not explain the two - mechanism synthesis.

Answer:

1. helicase
2. requires a template for the synthesis of DNA
3. Add a short sequence of complementary RNA to the existing DNA strand
4. the strands are oriented in opposite directions