Warm Up!1.What kind of biomolecule is

DNA?2.What function does it have?3.What are the building blocks?

DNA (DEOXYRIBONUCLEIC ACID)

Nucleic acid that composes chromosomes and carries genetic information.

CHROMOSOME ORGANIZATION1. A chromosome is an enormous

strand of super coiled DNA.2. Sections of DNA on the

chromosome that code for proteins are called genes.

BUILDING BLOCKS OF DNA

Composed of nucleotides Nucleotides contain three parts

5-Carbon Sugar (deoxyribose) Phosphate Group Nitrogen Base (four types, adenine,

guanine, thymine and cytosine)

• 4 types of Nitrogen Bases• adenine (A),• guanine (G), • cytosine (C), • thymine (T)

Nucleotides join together in long chains to form DNA

Complimentary base pairs—* A pairs with T* G pairs with

Adenine (A)Guanine (G) Thymine (T)Cytosine (C)

Specific base pairing arrangement (Chargaff’s Rule) A-T C-G

The amount of adenine = amount of thymine

The amount of guanine = amount of cytosine

STRUCTURE OF DNA

Consists of two strands of nucleotides that form a twisted ladder (double helix)

Sugar and phosphate alternate along the sides of the ladder (linked by strong covalent bonds)

Pairs of nitrogen bases form the rungs of the ladder (linked by weak hydrogen bonds).

The structure of DNA was discovered by Watson and Crick.

FUNCTION OF DNA

DNA codes for proteins (structural proteins, enzymes, and hormones)

information for building proteins is carried in the sequence of nitrogen bases

proteins determine physical and metabolic traits and regulate growth and development.

Stated Clearly – DNA

DNA REPLICATIONProcess in which DNA is copied

PURPOSE OF DNA REPLICATIONGives daughter cells produced by cell division a

complete set of genetic information identical to the parent cell.

WHERE REPLICATION

OCCURS

Nucleus

WHEN DURING THE CELL CYCLE

REPLICATION OCCURS

Interphase (S)

HOW REPLICATION OCCURS Helicase enzymes unzip the parent strand

by separating the nitrogen base pairs. DNA polymerase pairs free DNA

nucleotides with the exposed bases on both strands following the base pair rules.

each strand from the parent molecule serve as a template

3. Hydrogen bonds reform sealing the two strands of each DNA molecule together.

RESULTS OF REPLICATIONTwo molecules of DNA that are identicalEach is half old (strand from parent) and half new

(strand synthesized by DNA polymerase) – Semi-conservative process

Few mistakes (mutations) are made

Think about it…

If 30% adenine is present in an organism, then what is the percentage of thymine?

What is the remain percentage of nitrogen bases?

What percent of the remaining is cytosine? How do you know?

Think about it

30% thymine40% remaining20% cytosine (same amt of cytosine as guanine, and adenine and thymine make up 60% of organisms nitrogen bases)