DNA DeoxyriboNucleic Acid

DNA must

1 Store information

2 Copy information

3 Transmit information

DNA

Erwin Chargaff

Cs = Gs and As = Ts

of A T C Grsquos vary from one species to another

Page 2

Lesson Overview The Structure of DNA

Nucleic Acids and Nucleotides

Nucleotides

bull sugar (deoxyribose) a phosphate group and base

bull can be joined together in any order

Lesson Overview The Structure of DNA

Base Pairing

bull A with T

bull G with C

bull complementary

Lesson Overview The Structure of DNA

Hydrogen Bonding

bull Hydrogen bonds

form between

bases holds 2

strands together

bull H-bonds are

weak ndash allows

them to break

easily for

replication

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Erwin Chargaff

Cs = Gs and As = Ts

of A T C Grsquos vary from one species to another

Page 2

Lesson Overview The Structure of DNA

Nucleic Acids and Nucleotides

Nucleotides

bull sugar (deoxyribose) a phosphate group and base

bull can be joined together in any order

Lesson Overview The Structure of DNA

Base Pairing

bull A with T

bull G with C

bull complementary

Lesson Overview The Structure of DNA

Hydrogen Bonding

bull Hydrogen bonds

form between

bases holds 2

strands together

bull H-bonds are

weak ndash allows

them to break

easily for

replication

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Lesson Overview The Structure of DNA

Nucleic Acids and Nucleotides

Nucleotides

bull sugar (deoxyribose) a phosphate group and base

bull can be joined together in any order

Lesson Overview The Structure of DNA

Base Pairing

bull A with T

bull G with C

bull complementary

Lesson Overview The Structure of DNA

Hydrogen Bonding

bull Hydrogen bonds

form between

bases holds 2

strands together

bull H-bonds are

weak ndash allows

them to break

easily for

replication

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Lesson Overview The Structure of DNA

Base Pairing

bull A with T

bull G with C

bull complementary

Lesson Overview The Structure of DNA

Hydrogen Bonding

bull Hydrogen bonds

form between

bases holds 2

strands together

bull H-bonds are

weak ndash allows

them to break

easily for

replication

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Lesson Overview The Structure of DNA

Hydrogen Bonding

bull Hydrogen bonds

form between

bases holds 2

strands together

bull H-bonds are

weak ndash allows

them to break

easily for

replication

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Lesson Overview The Structure of DNA

Bonding

bull A ndash T ndash 2 H-bonds

bull G with C = 3 H-

bonds

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

Lesson Overview The Structure of DNA

The Replication Process

bull Each strand of DNA serves as a template or model for a

new strand

bull Helicase (enzyme) separates ldquounzipsrdquo - breaks H-bonds

between strands

bull DNA polymerase (enzyme) that joins new nucleotides to

existing DNA strand ndash if A adds Thellip if G adds Chellip etc

bull also ldquoproofreadsrdquo each new strand

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

DNA Replication

1 Helicase (enzyme) unzips DNA ndash breaking hydrogen bonds

2 DNA polymerase adds nucleotides to old DNA strand according to base-pairing rules

3 DNA polymerase proofreads each new strand

Telomeres

Tips of chromosomes

Difficult to replace

Prevents genes from being lost

DNA Replication Videos

HHMI

DNA Replication Videos

HHMI