Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

8. DNA Replication

Overview of DNA Replication

Genetics

8. DNA Replication

Overview of DNA Replication

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2:48 minutes

Problem 33a

Textbook Question

What would be the effects on DNA replication if mutation of DNA pol III caused it to lose each of the following activities?
5' to 3' polymerase activity

Verified step by step guidance

Understand the role of DNA polymerase III in DNA replication: DNA polymerase III is the primary enzyme responsible for synthesizing new DNA strands by adding nucleotides in the 5' to 3' direction during replication.

Recognize the importance of 5' to 3' polymerase activity: This activity allows DNA pol III to add nucleotides to the growing DNA strand by forming phosphodiester bonds between the 3' hydroxyl group of the last nucleotide and the 5' phosphate group of the incoming nucleotide.

Consider the consequences of losing 5' to 3' polymerase activity: Without this activity, DNA pol III would be unable to synthesize new DNA strands, effectively halting the elongation process during replication.

Analyze the broader impact on DNA replication: The inability to synthesize new DNA strands would prevent the replication fork from progressing, leading to incomplete replication of the genome and potentially causing cell cycle arrest or cell death.

Conclude the significance of this mutation: The loss of 5' to 3' polymerase activity in DNA pol III would be a critical defect, as it would disrupt the fundamental process of DNA replication, which is essential for cell division and genetic inheritance.

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Key Concepts

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

DNA Polymerase III Function

DNA Polymerase III is the primary enzyme responsible for DNA synthesis during replication in prokaryotes. It adds nucleotides to the growing DNA strand in a 5' to 3' direction, ensuring accurate and efficient replication of the genetic material. Understanding its role is crucial for analyzing the consequences of any mutations affecting its activity.

5' to 3' Directionality

DNA replication occurs in a specific direction, with new nucleotides being added to the 3' end of the growing strand, which means the template strand is read in the 3' to 5' direction. This directionality is essential for the proper synthesis of the leading and lagging strands, and any loss of 5' to 3' polymerase activity would disrupt this process, leading to incomplete or erroneous DNA strands.

Consequences of Mutations

Mutations in essential enzymes like DNA Polymerase III can lead to severe consequences for cellular function. If the 5' to 3' polymerase activity is lost, DNA replication would be halted, resulting in cell cycle arrest, genomic instability, and potentially cell death. Understanding these consequences helps in grasping the importance of enzyme activities in maintaining genetic integrity.

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Related Practice

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.

If the RNA primer consists of eight nucleotides, what is its base sequence?

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

DNA replication in early Drosophila embryos occurs about every 5 minutes. The Drosophila genome contains approximately 1.8×10⁸ base pairs. Eukaryotic DNA polymerases synthesize DNA at a rate of approximately 40 nucleotides per second. Approximately how many origins of replication are required for this rate of replication?

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Textbook Question

What would be the effects on DNA replication if mutation of DNA pol III caused it to lose each of the following activities?

3′ to 5′ exonuclease activity

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Textbook Question

Suppose that future exploration of polar ice on Mars identifies a living microbe and that analysis indicates the organism carries double-stranded DNA as its genetic material. Suppose further that DNA replication analysis is performed by first growing the microbe in a growth medium containing the heavy isotope of nitrogen (¹⁴N) that the organism is then transferred to a growth medium containing the light isotope of nitrogen (¹⁴N) and that the nitrogen composition of the DNA is examined by CsCl ultracentrifugation and densitometry after the first, second, and third replication cycles in the ¹⁴N-containing medium. The results of the experiment are illustrated here for each cycle. The control shows the positioning of the three possible DNA densities. Based on the results shown, what can you conclude about the mechanism of DNA replication in this organism?

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Textbook Question

The following diagram shows the parental strands of a DNA molecule undergoing replication.

Draw the daughter strands present in the replication bubble, indicating:

a. The polarity of daughter strands

b. The leading and lagging strands

c. Okazaki fragments

d. The locations of RNA primers

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Multiple Choice