Chapter 10 NotesStructure of DNA

Structure of DNADNA is Made up repeating units of nucleotides

Three parts of a Nucleotide are:

1. Deoxyribose sugar

2. Phosphate group

3. Nitrogen-containing base

Nitrogen Containing Bases

Base Pairing RulesAdenine pairs with Thymine (2 hydrogen bonds)

Guanine pairs with Cytosine (3 hydrogen bonds)

Chargaff’s Rule: The amount of adenine always equals the amount of thymine, and the amount of guanine equals cytosine.

The Double Helix

Double stranded, coiled like a spiral stair

The backbone of the strands are alternating phosphate and deoxyribose sugars

Histones

DNA is tightly coiled around proteins called histones to make the long DNA molecule easier to manage.

What are the three parts of a nucleotide?

What Base Bonds to Adenine?

What Base Bonds to Guanine?

Assignment

Class work: DNA Book– cover page and page 1 (Due tomorrow)

Homework: PQRST pg. 200-203 (due Friday)

Purpose of DNA Replication

Why would DNA replicate?

When would DNA replication occur?

To make a copy of it’s DNA for the cell to divide.

Mitosis

Steps of DNA Replication

1. Helicase unzips and unwinds the DNA strands by breaking the hydrogen bonds

Steps of DNA Replication

2. Enzymes called DNA Polymerase add complementary nucleotides.

Steps of DNA Replication

3. Process continues until entire strand is copied

Result is two strands of DNA

AAT CC A AA G

A T T T T TGG C

1. First the DNA must unzip: Enzymes split apart the base pairs and unwind the DNA.

AAT CC A AA G

A T T T T TGG C

AAT CC A AA G

A T T T T TGG C

AAT CC A AA G

A T T T T TGG C

TT

2. Bases pair up: Free nucleotides in the cell find their complementary bases along the original strand.

AAT CC A AA G

A T T T T TGG C

T

A C

T

AAT CC A AA G

A T T T T TGG C

T A

C T

AT

AAT CC A AA G

A T T T T TGG C

T A

C T

A

T

C

G

AAT CC A AA G

A T T T T TGG C

T A

C T

A

T

C

G

A C A

TGT

T

G

AAT CC A AA G

A

A T T T T TGG C

T A

C T

A

T

C

G

A C A

TGTT

G

A

AAT CC A AA G

A

A T T T T TGG C

T A

C T

A

T

C

G

A C A

TGTT

G

A

The DNA is now duplicated:

End Result

Two identical molecules of DNA

They have one new and one old strand

Mechanism of DNA Replication

DNA is said to be semiconservative since each new DNA molecule made has one parent strand and one daughter strand.

Can also be said: one old strand and one new strand

Accuracy and RepairCopies must be 100% accurate

Mutation= change in nucleotide at one location

Enzymes proofread and fix errors

Class work

Homework

DNA Replication worksheet1. Answer questions at the top2. Use page 201 to create a labeled drawing of DNA Replication with descriptions of each step

Page 2 of DNA Book (due Monday)PQRST (due tomorrow)