How DNA works

What was the conservative model of DNA replication?

The original double helix remained intact and instructed the formation of a new, identical double helix made entirely of new material.

What was the semiconservative model of DNA replication?

The DNA 'unzipped' and new nucleotides aligned along each strand so that each new double helix contained one strand of the original DNA and one strand of new material.

Which DNA replication model was proposed by Watson and Crick?

The semiconservative replication model.

In the Watson and Crick model, how does the DNA double helix unzip?

Along the hydrogen bonds between complementary base pairs, allowing semiconservative replication.

Which enzyme unzips the two strands of DNA?

DNA helicase.

What is the role of DNA helicase in replication?

It unzips the two strands of the DNA molecule along the hydrogen bonds.

What happens after DNA strands unzip?

Each strand acts as a template for the formation of a new complementary strand.

What ensures complementary base pairing in DNA replication?

The rule that cytosine always pairs with guanine and adenine always pairs with thymine.

How are new nucleotides added to the template strand?

Free DNA nucleotides align with exposed bases, forming new hydrogen bonds with complementary bases.

Which enzyme lines up and joins nucleotides along the template strand?

DNA polymerase.

What is the role of DNA polymerase in replication?

Lines up and catalyses the linking of nucleotides along the template strand.

Which enzyme joins together the sugar-phosphate backbones of DNA?

DNA ligase.

What is the role of DNA ligase in replication?

Catalyses the formation of phosphodiester bonds between the two strands of DNA.

What is the end result of DNA replication?

Two new DNA molecules identical to the original, each containing one original strand and one new strand.

How does the DNA molecule regain its double helix shape after replication?

It coils automatically as weak hydrogen bonds reform within the structure.

DNA helicase

An enzyme involved in DNA replication that unzips the two strands of the DNA molecule.

DNA polymerase

An enzyme involved in DNA replication that lines up and catalyses the linking up of nucleotides along the template strand.

DNA ligase

An enzyme involved in DNA replication that catalyses the formation of phosphodiester bonds between the two strands of DNA.