• THE CHEMISTRY OF HEREDITY (11.1) • DNA REPLICATION (11.1) DNA
• THE CHEMISTRY OF HEREDITY (11 .1)• DNA REPLICATION (11 .1)
DNA
• WHERE DO ALL CELLS COME FROM (CELL THEORY)?
• WHAT IS HEREDITY?
Answer these questions:
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?
The Chemistry of Heredity
DNA controls protein synthesisGenes make up DNAGenes control the formation of protein
Genetics The study of genes Why characteristics appear The processes of heredity
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
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?
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
The Chemistry of Heredity
There are 4 types of nucleotides, differing only in the nitrogenous baseAdenine (A)Guanine (G)Cytosine (C)Thymine (T)
A and G are called purines
C and T are called pyrimidines
Purines
Adenine (A) and Guanine (G) are composed of two rings
Pyrimidines
Cytosine (C) and Thymine (T) are composed of one ring
The Chemistry of Heredity
The nitrogen containing base (purines and pyrimidines) attaches to deoxyribose (5-carbon sugar) to form a ‘nucleoside’
Deoxyribose
To keep track of where things attach, we number the carbons
Nucleoside
Answer this question:
Which carbon is the nitrogen base attached to?
The Chemistry of Heredity
A nucleotide is a nucleoside with an attached phosphate group (attached where?)
The Chemistry of Heredity
Phosphate groups join the deoxyribose sugars together in a chain-like fashion
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?
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)
•
•WHAT KIND OF BONDS HOLD THE TWO STRANDS IN DNA TOGETHER?
• WHAT ARE THE 4 BASES AND HOW ARE THEY CATEGORIZED?
• WHAT DOES AN ENZYME DO?
Answer these questions:
DNA Replication
DNA replication is the process whereby an entire double-stranded DNA is copied to produce a second, identical DNA double helix
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/animations/dna_replication/index.html
DNA Replication
DNA Replication Proteins Helicase
Unwinds the DNA double helix into 2 individual strands Single-stranded binding proteins (SSBs)
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
DNA Replication
DNA Replication Proteins DNA Polymerase
Strings nucleotides together to form a new DNA strand RNAse H
Removes the RNA primers (set by primase) DNA ligase
Links short stretches of DNA together to create one long continuous DNA strand
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
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
New Strand Synthesis
1. Primase copies a short stretch of the DNA strand, creating a complementary RNA segment, showing DNA polymerase where to start
New Strand Synthesis
2. DNA polymerase can now begin synthesizing a new complimentary DNA strand
1. Two DNA polymerase enzymes are required, one for each strand
2. Since the strands are antiparallel, the DNA polymerase enzymes begin to move in opposite directions
3. One DNA polymerase copies continuously in one direction. This strand is called the leading strand
4. The other must synthesize in small fragments. This strand is called the lagging strand
1. The small fragments are called Okazaki fragments
New Strand Synthesis
3. RNAse H removes the primers (set by primase)4. The gaps left by the primers are filled by DNA
polymerase5. Finally, the Okazaki fragments are joined by
DNA ligase
http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html
http://www.youtube.com/watch?v=5VefaI0LrgE