1. DNA
• THE CHEMISTRY OF HEREDITY (11.1)
• DNA REPLICATION (11.1)

2. Answer these questions:
• WHERE DO ALL CELLS COME FROM (CELL THEORY)?
• WHAT IS HEREDITY?

3. The Chemistry of Heredity
 Heredity
 The passing of traits to offspring from parents
 Traits
 Physical and chemical characteristics
 The result of protein synthesis
 Answer this question:
 What controls protein synthesis?

4. The Chemistry of Heredity
 DNA controls protein synthesis
 Genes make up DNA
 Genes control the formation of protein
 Genetics
 The study of genes
 Why characteristics appear
 The processes of heredity

5. The Chemistry of Heredity
 Answer these questions:
 What makes two proteins different? (Hint: think primary
structure)
 Where are proteins assembled?
 Proteins differ by amino acid arrangement
 The order of amino acids
 Proteins are assembled at the ribosome
 Genes tell the sequence of amino acids
 The sequence is read at the ribosome
 The ribosome joins the amino acids in the proper order

6. The Chemistry of Heredity
 The Discovery of DNA
 Answer these questions:
 What is the monomer of DNA?
 What are the 4 monomers found in DNA?

7. The Chemistry of Heredity
 Deoxyribonucleic acid (DNA) – The Double Helix
 DNA is a polymer
 The monomer units of DNA are nucleotides
 Each nucleotide is made of a:
5-carbon sugar (deoxyribose)
 Nitrogen containing base
 Phosphate group


8. The Chemistry of Heredity
 There are 4 types of nucleotides, differing only in the nitrogenous
base
 Adenine (A)
 Guanine (G)
 Cytosine (C)
 Thymine (T)
 A and G are called purines
 C and T are called pyrimidines

9. Purines
 Adenine (A) and Guanine (G) are composed of two
rings

10. Pyrimidines
 Cytosine (C) and Thymine (T) are composed of one
ring

11. The Chemistry of Heredity
 The nitrogen containing base (purines and
pyrimidines) attaches to deoxyribose (5-carbon
sugar) to form a ‘nucleoside’

12. Deoxyribose
 To keep track of where things attach, we number the
carbons

13. Nucleoside
Answer this question:
Which carbon is the
nitrogen base attached to?

14. The Chemistry of Heredity
 A nucleotide is a nucleoside with an attached
phosphate group (attached where?)

15. The Chemistry of Heredity
 Phosphate groups join
the deoxyribose sugars
together in a chain-like
fashion

16. The Chemistry of Heredity
 DNA is made of 2 complimentary chains of
nucleotides where…

A forms 2 hydrogen bonds with T

G forms 3 hydrogen bonds with C

The bases (A, T, G, C) are hydrophobic

Where will they go?

19. The Chemistry of Heredity
 The series of nucleotide units makes one organisms’
DNA different from another
 Different DNA = Different Traits
 Every cell of a multicellular organism has the same
DNA (remember, we all start as one cell)

20. Answer these questions:
•W H A T K I N D O F B O N D S H O L D T H E T W O S T R A N D S I N D N A
TOGETHER?
• WHAT ARE THE 4 BASES AND HOW ARE THEY
CATEGORIZED?
• WHAT DOES AN ENZYME DO?

21. DNA Replication
 DNA replication is the
process whereby an
entire double-stranded
DNA is copied to
produce a
second, identical DNA
double helix

22. DNA Replication
 The Replication Factory
 DNA replication is carried out by proteins
 These special proteins cluster together ( replication factory)
 DNA is fed through the replication factory
 The incoming DNA double helix is split into two single strands
and each original single strand becomes half of a new DNA
double helix


This is a semi-conservative process
http://www.wiley.com/college/pratt/0471393878/student/ani
mations/dna_replication/index.html

23. DNA Replication
 DNA Replication Proteins
 Helicase


Single-stranded binding proteins (SSBs)


Unwinds the DNA double helix into 2 individual strands
Coats the single-stranded DNA, preventing the two strands from
realigning
Primase

Gets each strand ready (or primed) for replication by adding a
small amount of RNA to each strand to show DNA polymerase
where to start

24. DNA Replication
 DNA Replication Proteins
 DNA Polymerase


RNAse H


Strings nucleotides together to form a new DNA strand
Removes the RNA primers (set by primase)
DNA ligase

Links short stretches of DNA together to create one long
continuous DNA strand

25. DNA Replication
 Step 1: Strand Separation
 The two strands that make up the double helix are unwound
and separated by the enzyme helicase
 Single-stranded binding proteins (SSBs) quickly coat
the newly exposed single strands

Without the SSBs, the complementary DNA strands could easily
snap back together

26. DNA Replication
 Step 2: New Strand Synthesis
 The two single strands of DNA act as templates for the
production of two new, complimentary DNA strands
 The two strands that makes up a double helix are
antiparallel


Complementary 5’ to 3’ strands running in opposite directions
Strand synthesis proceeds in a 5’ to 3’ direction

28. New Strand Synthesis
1. Primase copies a short stretch of the DNA
strand, creating a complementary RNA
segment, showing DNA polymerase where to start

29. New Strand Synthesis
2. DNA polymerase can now begin synthesizing a
new complimentary DNA strand
Two DNA polymerase enzymes are required, one for each
strand
Since the strands are antiparallel, the DNA polymerase
enzymes begin to move in opposite directions
One DNA polymerase copies continuously in one direction.
This strand is called the leading strand
The other must synthesize in small fragments. This strand is
called the lagging strand
1.
2.
3.
4.
1.
The small fragments are called Okazaki fragments

30. New Strand Synthesis
3. RNAse H removes the primers (set by primase)
The gaps left by the primers are filled by DNA
polymerase
5. Finally, the Okazaki fragments are joined by DNA
ligase
4.
http://www.wiley.com/college/pratt/0471393878/student/animations/d
na_replication/index.html
http://www.youtube.com/watch?v=5VefaI0LrgE