14. DNA Synthesis

Introduction to DNA Replication

DNA Structure and Replication: Crash Course Biology #10

 Bacterial chromosomes have a single origin of replication, but eukaryotic chromosomes have many origins. 

 No. This statement is true, but there is a better answer. 

 The DNA sequence at the origin of replication is recognized by specific proteins that bind to the origin. 

 The two strands of DNA at the origin of replication are separated, creating a replication bubble. 

 Replication proceeds in both directions from each origin. 

 All of the listed responses are correct. 

Review the details of DNA replication. What events have to occur to start replication?

Which of the following statements about replication origins is/are correct?

DNA Replication: Copying the Molecule of Life

Animation: DNA Replication: An Overview

DNA Replication Overview

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
a. DNA polymerase
b. DNA ligase
c. Okazaki fragments
d. primase

Unwinding the DNA: Topoisomerase, Helicase & SSBs

 Its helical nature and hydrogen bonding 

 No. DNA's helical nature is not crucial to its duplication. 

 Its phosphodiester linkages and complementary strands 

 No. The phosphodiester linkages are not crucial to its duplication. 

 Its deoxyribose sugar and phosphate groups 

 No. The sugar and phosphate groups, though important in the backbone structure of DNA, do not play an important role in the copying of DNA. 

 No. It doesn't matter what the sequence of bases is. The structure of DNA guarantees that the sequence of bases that exists will be accurately copied. 

 Its specific base pairing through hydrogen bonds 

The ability to make accurate copies had to be inherent in DNA's structure.

Which of the following attributes of DNA is most crucial to its accurate duplication?

Components of DNA Replication

 The DNA molecules of bacterial chromosomes have a slightly different structure than those of eukaryotic chromosomes. 

 No. The molecular structure of DNA is the same in all organisms. 

 Eukaryotes have a single circular chromosome, whereas bacteria have several linear chromosomes. 

 Bacterial chromosomes have much more protein associated with the DNA than eukaryotes. 

 No. Bacterial chromosomes actually have less protein associated with the DNA. 

 There is no difference between bacterial and eukaryotic chromosomes. 

 No. Though the DNA itself has the same structure, there are differences in the structure of the chromosomes, which consist of DNA and proteins. 

 Bacteria usually have a single circular chromosome whereas eukaryotes have several linear chromosomes. 

Is it the DNA or something else?

What is the major difference between bacterial chromosomes and eukaryotic chromosomes?

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Which meristem was likely affected in the chinaberry tree?

Origin of Replication

BioFlix: DNA Replication

DNA replication forks begin forming at the origin of replication (ORI).

DNA replication forks are caused by helicase separating two complementary strands of DNA.

There are two replication forks found in each replicating prokaryotic chromosome.

DNA replication forks are found at both ends of the replication “bubble”.

Which of the following is incorrect regarding DNA replication forks?

Relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix.

Elongating new DNA at a replication fork by adding nucleotides to the existing chain.

Reattaching the hydrogen bonds between the base pairs in the double helix.

Building RNA primers using the parental DNA strand as a template.

What is the function of the enzyme topoisomerase in DNA replication?

Replication Forks

 sometimes faster and sometimes slower than 

 The rates are not comparable because elongation only occurs in prokaryotes. 

 No. Elongation occurs in both prokaryotes and eukaryotes. 

The eukaryotic replication machinery is more complex than the prokaryotic machinery.

In prokaryotes, the rate of elongation during DNA replication is __________ the rate in eukaryotes.

 No. This is a site where replication begins, and it is therefore present at the center of the replication bubble. 

 No. The movement of replication bubbles along the chromosome does not depend on the presence of genes. 

 No. A telomere would be found at only one end of a replication bubble, if at all. 

 No. Ribosomes carry out protein synthesis. 

Review the details of DNA replication.

At each end of a DNA replication bubble is __________.

DNA Replication

 the reaction is catalyzed by RNA polymerase 

 No. DNA polymerase catalyzes DNA synthesis. 

 No. Although the error rate may by low, replication is not error-free. 

 only one strand of the molecule acts as a template 

 No. DNA replication occurs during interphase. 

 both strands of a molecule act as templates 

Consider the work of Meselson and Stahl.

During the replication of DNA, __________.

DNA Replication (Updated)

DNA replication - 3D

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