Structure and Role of DNA

What does DNA stand for?

Deoxyribonucleic Acid

What type of biomolecule is DNA?

A nucleic acid

Where is DNA found in eukaryotic cells?

In the nucleus

What is the main role of DNA?

To store and carry genetic information

What does DNA act as in protein synthesis?

The blueprint for building all proteins

What determines the characteristics of an organism?

Its DNA

What is the overall shape of DNA?

A double helix.

What forms the “backbone” of the DNA structure?

Deoxyribose sugar + phosphate group

What connects the two strands of DNA?

Complementary nitrogenous bases linked by hydrogen bonds

What keeps the two DNA strands parallel?

Complementary base pairing

Who discovered the structure of DNA?

James Watson and Francis Crick

What technique was used to reveal DNA’s structure?

X-ray crystallography

In what year was the DNA structure discovered?

1953

What is the basic unit of DNA?

A nucleotide

Why are nucleic acids called “polynucleotides”?

They are long chains composed of many nucleotides

What are the three parts of a nucleotide?

Deoxyribose sugar, phosphate group, nitrogenous base

What are the four nitrogenous bases in DNA?

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

Which bases are purines?

Adenine and Guanine

Which bases are pyrimidines?

Cytosine and Thymine

What base pairs with Adenine?

Thymine

What base pairs with Cytosine?

Guanine

What bonds hold nitrogenous bases together?

Hydrogen bonds

What rule states that A pairs with T and C pairs with G?

The complementary base pairing rule

What are chromosomes made of?

DNA

What is DNA made of?

Linearly arranged genes

What happens to chromosomes after the S phase of interphase?

Each chromosome has two sister chromatids joined at the centromere

What is a chromatid?

A long DNA molecule wrapped around histone proteins

What is a gene?

A specific segment of DNA that controls hereditary traits

How long can a gene be?

Around 3,000 base pairs

How many nitrogenous base pairs are in the complete human genome?

~3.2 billion base pairs

How many chromosomes does a human body cell have?

46 chromosomes (23 pairs)

How many genes do humans approximately have?

About 35,000 genes

Where are genes arranged on chromosomes?

Linearly along the chromosome’s length

When does DNA replication occur?

During the S phase of interphase

Why does DNA replicate before cell division?

To ensure chromosomes are duplicated for daughter cells

What process allows chromosome duplication?

DNA replication

Why is complementary base pairing important?

It ensures accurate DNA replicatio

What makes one organism different from another genetically?

The specific sequence of nitrogenous bases.

Why is DNA considered a “complex polymer”?

It’s made of long chains of repeating nucleotide units