Chapter 25, Problem 1E

Summary Introduction

To calculate: How many Okazaki fragments are synthesized in a replication of the E.coli chromosome.

Introduction: The new DNA fragments that are synthesized on the lagging strand that are relatively short and irregular during the DNA replication is called as Okazaki fragments. The lagging strand is also called discontinuous strand as it irregularly synthesizes Okazaki fragments. E.coli has only one ori region and the length of the Okazaki fragments are much longer than that of eukaryotes.

Explanation of Solution

Calculation:

Given:

The total genome content of E.coli chromosome=4×10⁶ base pairs.

The length of Okazaki fragments=1000-2000 nucleotides.

The number of Okazaki fragments that are required for E.coli chromosome can be calculated using the following equation:

$\begin{array}{c}\text{No}\text{.}\text{of}\text{okazaki}\text{fragments}\text{=}\frac{\text{Total}\text{genome}\text{content}}{\text{Length}\text{of}\text{okazaki}\text{fragment}\text{in}\text{DNA}}\\ \text{=}\frac{\text{4}{\text{.6×10}}^{\text{6}}\text{bp}}{\text{1000-2000}\text{nt}}\\ \text{=2300-}\text{4600}\text{fragments}\end{array}$

Therefore, the number of Okazaki fragments that are required for E.coli chromosome is equal to 2300-4600 fragments.

Conclusion

Conclusion: 2300-4600 Okazaki fragments are synthesized in a replication of the E.coli chromosome.