Molecular Genetics

Who discovered the structure of DNA?

James Watson and Francis Crick.

What does the DNA model consist of?

Two strands of nucleotides.

What are the three components of a nucleotide?

A deoxyribose sugar, a phosphate group, and a nitrogen base.

How many different nucleotides are there in DNA?

Four different nucleotides.

What represents the DNA structure?

A twisted ladder, also known as a double helix.

What forms the backbone of the DNA molecule?

Sugar and phosphates.

What provides the rationale for how base pairs are paired in DNA?

Complementary base pairing.

Which nitrogen bases are purines?

Adenine and guanine.

Which nitrogen bases are pyrimidines?

Thymine and cytosine.

What is the base pairing rule for adenine?

Adenine always bonds with thymine (A-T).

What is the base pairing rule for guanine?

Guanine always binds with cytosine (G-C).

What type of bonds hold the complementary base pairs together?

Hydrogen bonds.

How many hydrogen bonds are between adenine and thymine?

Two hydrogen bonds.

How many hydrogen bonds are between guanine and cytosine?

Three hydrogen bonds.

What is the term describing the orientation of the DNA strands?

Antiparallel.

What is the process called when DNA makes copies of itself?

DNA replication.

What ensures each daughter cell has an identical copy of DNA?

DNA replication occurs before cell division.

What is semiconservative replication?

The process where the parent DNA is used as a template to develop identical copies.

What is the role of DNA helicase in DNA replication?

It breaks the bonds between the nitrogen bases to separate the DNA strands.

What is formed when DNA strands separate?

A replication fork.

What is the leading strand in DNA replication?

The strand that is continuously replicated from 5’ to 3’.

What are Okazaki fragments?

Fragments of nucleotides added on the lagging strand during DNA replication.

What enzyme is responsible for adding nucleotides during DNA replication?

DNA polymerase III.

What does DNA polymerase I do?

Removes RNA primers and replaces them with DNA nucleotides.

What is the function of DNA ligase in DNA replication?

It joins the fragments of DNA together.

How do DNA polymerase I and III assist in proofreading?

They cut out mistakes and replace incorrect nucleotides with the correct ones.