DNA Structure

1
DNA Structure Replication

• Ch 9

2
DNA Structure Objectives

• Identify the full name of DNA. 
• List the basic building blocks of DNA. 
• List the three components of a nucleotide. 
• List the four nitrogen bases found in DNA. 
• Distinguish between a purine and a pyrimidine. 
• Explain the base-pairing rule. 
• Identify and explain the structure of DNA. 
• Identify the chemical bonds that connect nitrogen
  bases. 
• Recognize the power of the DNA molecule.

3
DNA Some Info

• DNA Deoxyribonucleic Acid
• Named for Deoxyribose the sugar in DNA
• Located in the nucleus of a cell.
• "Blueprint of Life." - keeps codes for proteins

4
DNA Shape

• Double helix twisted ladder
• Nucleotides are building blocks
• Group of a sugar (deoxyribose), a phosphate
  group, and a nitrogenous base
• 4 types of nucleotides because 4 kinds of bases 

5
Nucleotides Bonded Together

• What binds in the middle?
• 2. What makes up the outside of the ladder?
• 3. What atoms cause the bonds in the middle?

6
Where You Correct?

• Bases bind in the middle
• Phosphate and Sugar make up the outside of the
  ladder
• Hydrogen creates hydrogen bonds between the bases
  in the middle.

7
4 Nitrogenous Bases

• Purine two-ring structure. Adenine and Guanine
  are purines.
• Pyrimidines one-ring structure. Cytosine and
  Thymine are pyrimidines.
• Base Pairing Rules
• A binds w/ T
• C binds w/ G
• The Code is in the
  order of bases (ATCG)

8
DNA Structure Review

• What do the letters DNA stand for?
• What is the shape of the DNA molecule?
• DNA is composed of chains of ____.
• Identify one of the two chemicals (groups) that
  forms the backbone of the molecule.
• What chemicals form the rungs across the middle
  of the molecule?
• DNA is ____ - stranded.
• According to base-pairing, adenine joins with
  ____.
• Identify the sugar molecule found in DNA.
• Where is DNA located in the cell?
• Identify the bonds that join the nitrogen bases.

9
DNA Replication Objectives

• Describe the events during DNA replication.
• Know why is DNA replication referred to as
  semi-conservative.
• Be familiar with the different enzymes involved
  in DNA replication and their roles.
• Know what an origin of replication is and what
  role it plays in DNA replication.
• Understand the role do RNA primers play in DNA
  replication.
• Understand the pattern of complementary
  base-pairing.

10
Definition

• DNA replication The process of copying a cell's
  DNA, so that the cell has two, rather than one,
  copies of its DNA.
• Semi-conservative replication After
  replication, each new DNA consists of old and new
  strands.

11
3 Important Enzymes

• DNA helicase - "'walks" along the DNA molecule,
  opening the double helix as they move. Many
  replication forks occur.
• DNA polymerase - adds new nucleotides to a
  growing strand of DNA.
• DNA ligase puts together the new pieces of DNA
  that are made at each fork.

12
Complementary Base-Pairing
1
Starting at the 3 End, which nucleotides would
be added on and in what order?
2
3
4
5
6
7
8

• http//www.sci.uidaho.edu/bionet/biol115/t6_cell_g
  rowth/lesson02/activity_DNA-replication.htm

13
Where You Correct?

• The correct sequence was
• 5
• 8
• 4
• 8
• 4
• 1

14
Spell Check by DNA Polymerase
15
Replication Review

• What enzyme unzips DNA?
• Does DNA have 1 or many replication forks?
• What enzyme adds more nucleotides to the parent
  DNA strand?
• What enzyme puts the new pieces of DNA together?
• What enzyme proofreads DNA?
• Why is DNA considered semi-conservative?