1. Objectives: Describe the overall structure of DNA
Do Now
Take out your vocabulary and outline homework for 11.1
What organelle is known as the “control center” of the cell?
nucleus
What structures are found in the nucleus?
chromosomes
What are located on chromosomes?
Genes
What are chromosomes composed of?
DNA wound around proteins
Homework: Genes and DNA Reinforcement Guide
Objectives: Describe the overall structure of DNA

2. Objectives: Describe the overall structure of DNA
Chapter 11
Section 1
Objectives: Describe the overall structure of DNA

3. What do the following have in common?
Mitochondria
Humans
Frogs
Objectives: Describe the overall structure of DNA

4. Objectives: Describe the overall structure of DNA
They all contain DNA!
Objectives: Describe the overall structure of DNA

5. Objectives: Describe the overall structure of DNA
DNA Fun Facts!!!
Did You Know?:
Each one of your cells contains about
2-3 meters (8-10 feet) of DNA!
If you unraveled the DNA from all of
your cells, it would stretch to the
moon over 300,000 times!
Objectives: Describe the overall structure of DNA

6. Objectives: Describe the overall structure of DNA
What Does DNA Do?
DNA contains the genetic information for our cells.
Our DNA tells our cells what proteins to make.
The proteins determine how the cell functions.
So DNA ultimately controls all cellular functions.
Objectives: Describe the overall structure of DNA

7. Deoxyribonucleic Acid
The monomers of DNA are nucleotides.
Each nucleotide has three parts:
Draw this nucleotide in your notes!!
1. Phosphate
2. Sugar (Deoxyribose)
Phosphate
3. Nitrogen Base
Sugar
Nitrogen
Base
The nucleotides are put together during DEHYDRATION
SYNTHESIS reactions.

8. Objectives: Describe the overall structure of DNA
Nitrogen Bases
There are two different types of bases:
Purines (2 rings) – Adenine and Guanine
Pyrimidines (1 ring) – Thymine and Cytosine
Objectives: Describe the overall structure of DNA

9. Objectives: Describe the overall structure of DNA
Double Helix
DNA looks like a twisted ladder. It is composed of two strands of nucleotides bonded together.
The sides of the ladder are made of alternating sugars and phosphates.
The “rungs” of the ladder are made of nitrogen bases.
Objectives: Describe the overall structure of DNA

10. Objectives: Describe the overall structure of DNA
The Double Helix
Objectives: Describe the overall structure of DNA

11. How do we know about DNA’s shape?
The double helix is the model proposed by scientists James Watson and Francis Crick in They received a Nobel Prize in 1962 for their discovery
Watson and Crick’s model was supported by evidence from other scientists like Rosalind Franklin and Maurice Wilkins who studied X-ray photographs of DNA.
Objectives: Describe the overall structure of DNA

12. Bonding Patterns
The sugar-phosphate backbone is held together with strong covalent bonds.
The nitrogen bases are held together by weak hydrogen bonds.
The nitrogen bases bond in specific ways according to the Complementary Base Pairing Rule.
A & T will only bond together. They form 2 H bonds.
C & G will only bond together. They form 3 H bonds.
The sequence of bases on one strand, will complement the sequence of bases on the other.

13. So ALWAYS REMEMBER… 1. Adenine ALWAYS bonds with Thymine A-T
2. Cytosine ALWAYS bonds with Guanine
C-G
Objectives: Describe the overall structure of DNA

14. Objectives: Describe the overall structure of DNA
So…
IF we have a strand of DNA with the following code:
A T G G A A T C G A T
THEN, the sequence of the complementary strand will be…
T A C C T T A G C T A
Objectives: Describe the overall structure of DNA

15. Objectives: Describe the overall structure of DNA
Activity time!
On a blank piece of computer paper your are going to draw a small segment of DNA! Sugars – Red Adenine - Purple Phosphates – Black Thymine - Pink Guanine – Green Cytosine – Blue The segment of DNA going down the length of the left side of the paper will be as follows: A – G – C – A – A – T – C - G
Objectives: Describe the overall structure of DNA