• 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