The Human Genome – DNA Structure and Replication

Life depends on the ability of cells to translate the genetic instructions required to make and maintain a living organism. Indeed, these instructions are stored within every living cell in its deoxyribonucleic acid (DNA).

The most crucial advance made in the 1940s was the recognition that DNA is the carrier of the cell’s genetic information.

There has been a tremendous amount of progress in understanding DNA in recent years. The study of disease pathways, the identification of hereditary abnormalities, and the formulation of new drugs have all benefited from advances made possible by a better understanding of DNA’s structure and function.

In this lecture, we initially look at the DNA discovery from Watson and Cricks and describing the double helix structure and function of DNA. Furthermore, we focus in the types and structure of RNA and its importance. We look at DNA replication enzymes and DNA replication process in Prokaryotes and Eukaryotes, emphasizing the differences between them.

Understanding the importance of DNA replications and enzyme involved such as DNA polymerases and helicases will also make you appreciate more the complex biological processes that occur in a cell. This lecture points out the central dogma of molecular biology which is a theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.

You will be able to use this knowledge to understand more about personalized medicine which is revolutionizing the medicine by aiming to provide tailor-made prevention and treatment strategies for defined groups of individuals. Furthermore, you will gain a better understanding of the mechanisms of genetic diseases, such as single gene disorders like cystic fibrosis, which will be discussed in week 3.

The lecture will be divided into five different parts:

1. The structure of DNA

2. The structure and types of RNA

3. DNA replication enzymes

4. DNA replication in Prokaryotes

5. DNA replication in Eukaryotes

You will also be provided with reading materials “Further Reading 1.1- History of DNA discovery” and “Further Reading 1.2 – Meselson and Stahl: Models of DNA replication” where you can read about DNA semi-conservative model and answer few questions. The link to the reading list is shown under the recommended reading section.

The learning objectives for this lecture are:

· Know and understand the structure of DNA and the different conformations that DNA adopts. Be familiar with the factors that influence DNA conformation

· Explain the DNA replication process: Initiation, Elongation and Termination and the functions of the main enzymes involved in this process

· Describe the process of DNA unwinding and the role of DNA Helicase

· Identify the structure and the function of DNA Polymerase I, II and III

· Be able to explain the Meselson and Stahl experiment that shows the semi-conservative model of DNA

· Compare and contrast the difference between Prokaryotic and Eukaryotic DNA replication process

For this lecture, we recommend the following readings:

Recommended Reading:

1.Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid

2.The structure of DNA

3.Biochemistry, RNA Structure

4.DNA replication and recombination

5.The Replication of DNA in Escherichia Coli

6.Further Reading: The history of DNA and Meselson and Stahl: Models of DNA replication

Optional Reading:

1. Editorial: The DNA Replication Machinery as Therapeutic Targets

2. DNA replication: a complex matter

3. Origins of DNA replication

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