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Ch. 11 - DNA Replication and Recombination
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 11 - DNA Replication and RecombinationProblem 28a
Chapter 11, Problem 28a

Assume that the sequence of bases shown below is present on one nucleotide chain of a DNA duplex and that the chain has opened up at a replication fork. Synthesis of an RNA primer occurs on this template starting at the base that is underlined.
If the RNA primer consists of eight nucleotides, what is its base sequence?
3'.......GGCTACCTGGATTCA....5'

Verified step by step guidance
1
Identify the sequence of bases on the given DNA strand. The DNA strand serves as the template for RNA synthesis during replication.
Recall the base-pairing rules for RNA synthesis: Adenine (A) pairs with Uracil (U), Thymine (T) pairs with Adenine (A), Cytosine (C) pairs with Guanine (G), and Guanine (G) pairs with Cytosine (C).
Locate the underlined base in the DNA sequence, as this marks the starting point for RNA primer synthesis. The RNA primer will be synthesized in the 5' to 3' direction complementary to the DNA template strand.
Count eight nucleotides starting from the underlined base on the DNA strand. For each nucleotide in the DNA template, determine the complementary RNA base using the base-pairing rules.
Write out the sequence of the RNA primer, ensuring it consists of eight nucleotides and follows the complementary base-pairing rules.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Replication

DNA replication is the biological process by which a cell duplicates its DNA, allowing genetic information to be passed on during cell division. It involves unwinding the double helix structure of DNA at the replication fork, where each strand serves as a template for synthesizing a new complementary strand.
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Steps to DNA Replication

RNA Primer

An RNA primer is a short strand of RNA that provides a starting point for DNA synthesis during replication. It is synthesized by the enzyme primase and is essential because DNA polymerases cannot initiate synthesis without a primer. The primer is complementary to the DNA template strand and is later replaced by DNA nucleotides.
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RNA

Base Pairing Rules

Base pairing rules dictate how nucleotides pair in DNA and RNA. In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). In RNA, uracil (U) replaces thymine, so adenine pairs with uracil. Understanding these rules is crucial for determining the sequence of the RNA primer based on the DNA template.
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Base Distortions
Related Practice
Textbook Question

Assume a hypothetical organism in which DNA replication is conservative. Design an experiment similar to that of Taylor, Woods, and Hughes that will unequivocally establish this fact. Using the format established in Figure 11.5, draw sister chromatids and illustrate the expected results establishing this mode of replication.

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Textbook Question

DNA polymerases in all organisms add only 5' nucleotides to the 3' end of a growing DNA strand, never to the 5' end. One possible reason for this is the fact that most DNA polymerases have a proofreading function that would not be energetically possible if DNA synthesis occurred in the 3' to 5' direction.

Sketch the reaction that DNA polymerase would have to catalyze if DNA synthesis occurred in the 3' to 5' direction.

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Textbook Question

DNA polymerases in all organisms add only 5' nucleotides to the 3' end of a growing DNA strand, never to the 5' end. One possible reason for this is the fact that most DNA polymerases have a proofreading function that would not be energetically possible if DNA synthesis occurred in the 3' to 5' direction.

Consider the information in your sketch and speculate as to why proofreading would be problematic.

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Textbook Question

Assume that the sequence of bases shown below is present on one nucleotide chain of a DNA duplex and that the chain has opened up at a replication fork. Synthesis of an RNA primer occurs on this template starting at the base that is underlined.

In the intact RNA primer, which nucleotide has a free 3'-OH terminus?

3'.......GGCTACCTGGATTCA....5'

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Textbook Question

Reiji and Tuneko Okazaki conducted a now classic experiment in 1968 in which they discovered a population of short fragments synthesized during DNA replication. They introduced a short pulse of ³H-thymidine into a culture of E. coli and extracted DNA from the cells at various intervals. In analyzing the DNA after centrifugation in denaturing gradients, they noticed that as the interval between the time of ³H-thymidine introduction and the time of centrifugation increased, the proportion of short strands decreased and more labeled DNA was found in larger strands. What would account for this observation?

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Textbook Question

Consider the drawing of a dinucleotide below.

Is it DNA or RNA?

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