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
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?
17.
18.
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
27.
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