Question

dna replication practice & review
name chisam
model 2 – dna replication
direction of dna
helicase
free nucleotides
dna helicase

1. examine model 2 as well as your notes on the dna replication process. number the steps below in sequential order to describe the replication of dna in a cell.

______ dna twists back into the double helix conformation
______helicase enzyme breaks the hydrogen bonds holding opposite strands together.
______two strands of dna now present, both half “old,” or template dna, and half “new” dna.
______ dna polymerase enzyme adds free nucleotides to the exposed bases on the template strand, according to chargaff’s rule.
______ strands of dna separate.
______dna polymerase proofreads nitrogen base pairing to find and correct any mistakes

1. locate the dna helicase on model 2.

a. what type of organic compound is dna helicase?
b. what is the role of dna helicase in the replication of dna?

1. what rule is used to join free nucleotides to the exposed bases of the dna?

Explanation:

Question 1 (Ordering DNA Replication Steps)

Step1: Identify the first step

The first step in DNA replication is the action of helicase. So "Helicase enzyme breaks the hydrogen bonds holding opposite strands together." is step 1.

Step2: Next step after helicase action

After helicase breaks bonds, "Strands of DNA separate." occurs. This is step 2.

Step3: Then DNA polymerase adds nucleotides

Next, "DNA polymerase enzyme adds free nucleotides to the exposed bases on the template strand, according to Chargaff’s rule." is step 3.

Step4: Proofreading by DNA polymerase

After adding nucleotides, "DNA polymerase proofreads nitrogen base pairing to find and correct any mistakes" happens. Step 4.

Step5: Formation of new DNA strands

Then, "Two strands of DNA now present, both half “old,” or template DNA, and half “new” DNA." is step 5.

Step6: Final step - re - forming double helix

Finally, "DNA twists back into the double helix conformation" is step 6.

So the order is: 6 (DNA twists back...), 1 (Helicase enzyme...), 5 (Two strands...), 3 (DNA polymerase...), 2 (Strands of DNA...), 4 (DNA polymerase proofreads...)

Enzymes are a type of protein, and DNA helicase is an enzyme. So DNA helicase is a protein (a type of organic compound).

DNA helicase's role is to break the hydrogen bonds between the complementary base pairs of the double - stranded DNA. This action separates the two strands of DNA, which is necessary to expose the template strands for the subsequent steps of DNA replication (like nucleotide addition by DNA polymerase).

Answer:

1. DNA twists back into the double helix conformation
2. Helicase enzyme breaks the hydrogen bonds holding opposite strands together.
3. Two strands of DNA now present, both half “old,” or template DNA, and half “new” DNA.
4. DNA polymerase enzyme adds free nucleotides to the exposed bases on the template strand, according to Chargaff’s rule.
5. Strands of DNA separate.
6. DNA polymerase proofreads nitrogen base pairing to find and correct any mistakes

Question 2a (Type of organic compound for DNA helicase)