QUESTION 1 1 points Save Anpwer Which of the following is a coerect statement re

Question

QUESTION 1 1 points Save Anpwer Which of the following is a coerect statement regarding DNA replication in vivo? ADNA regieation is nsated at the origin of repication in e DNA. OB. ANA polymerase nequires primers to iniate ONA synhesis Okazaki fragments are the short fragments of DNA that are produced on the lagging strand at the origin of the replication. O The 5' to 3 direction of DNA synthesis implies that deoxyribonucleotides are added to the 5' OH group on the growing strand. OE Bot A and B O Both A and C QUESTION 2 1 points Save Awer Polymerase chain reaction is known for its power of amplifying a target DNA sequence at a high speed. Each cycle can double the number of DNA molecules (target sequence). Which of the following is CORRECT regarding PCR? OA In order to make 10 copies of the DNA, you need at least 5 cycles of PCR. OB. Helicase is required to separate the two strands in PCR OC. Diseoxynucleotides are used in PCR. OD.DNA primers are needed in PCR OEAll of the above QUESTION 3 1 points Save Anwer You know part of a DNA sequence as follows: 3' GGCGTAACCAA...AAGTCC...CCGGTTG5' (the dashed lines represent the unknown nucleotides) Which of the following should be the primer if we want to make a complementary strand of the template? OA ScCGCAT3 QUESTION 4 1 points Save Answer Which enzymatic activity is common to all DNA polymerases? OA s to3 polymerase activity OB.3 to 5' polymerase activity OG sto3 exonuclease activity OD.J to 5 eNonuclease activity OE.Allot the above.

Explanation / Answer

Ans. #1. Correct option- E. (both A, B). DNA replication initiates at the origin of replication in the DNA. DNA polymerase can’t synthesize DNA on its own, it can only extent a pre-synthesized strand. The pre-synthesized strand, known as RNA primer, is synthesized by DNA primase- a type of RNA polymerase.

# Option C. Incorrect- Okazaki fragments are short stretches of DNA synthesized on the lagging strand. It is formed throughout the synthesis of lagging strand, but NOT limited to the origin of replication.

# Option D. Incorrect. The deoxyribonucleotides are added to the 3’-OH of the previous nucleotide.

#2. Correct option- D. DNA primers (forward and reverse primers) are needed in primer.

#Option A. Incorrect. The required number of cycles depend on the initial number of template DNA as well as the final required number of DNA. If there is only 1 template DNA, 4 cycles would produce 16 DNA molecules. SO, the required number of cycles assuming a single template DNA is 4. If there are 100 template DNA, a single PCR cycle would produce 100 new DNA.

# Option B. Incorrect. Helicases are not required in PCR. Instead, DNA is denatured (melted) thermally.

# Option C. Incorrect. Deoxyribonucleotides, but NOT di-deoxyribonucleotides are required in PCR.

# 3. Correct option- A. 5’-CCGCAT-3’

Two possible complementary strands would be-

            5’-CCGCATTGGTT-3’                        ;           3’-CAACCGG-5’

#4. Correct option. A. All DNA polymerases have 5’-3’ polymerase activity.

# Option B. Incorrect. DNA polymerases have only 5’-3’ polymerase activity.

# Option C, D- Incorrect. Not all DNA polymerases have these activities.

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