Do Now• Take out your vocabulary and outline homework for 11.1

1. What organelle is known as the “control center” of the cell?– nucleus

2. What structures are found in the nucleus?– chromosomes

3. What are located on chromosomes?– Genes

4. What are chromosomes composed of?– DNA wound around proteins

Homework: 11.1 Genes and DNA Reinforcement Guide

Objectives: Describe the overall structure of DNA

Chapter 11Section 1

Objectives: Describe the overall structure of DNA

What do the following have in common?

Mitochondria

Humans

Frogs

Objectives: Describe the overall structure of DNA

They all contain DNA!

Objectives: Describe the overall structure of DNA

DNA Fun Facts!!!

Did You Know?:

o Each one of your cells contains about

2-3 meters (8-10 feet) of DNA!o 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

What Does DNA Do?

o DNA contains the genetic information for our cells.

o Our DNA tells our cells what proteins to make.

o The proteins determine how the cell functions.

o So DNA ultimately controls all cellular functions.

Objectives: Describe the overall structure of DNA

Deoxyribonucleic Acid

The monomers of DNA are nucleotides.

Each nucleotide has three parts:

1. Phosphate2. Sugar (Deoxyribose)

3. Nitrogen Base

Phosphate

Sugar Nitrogen

Base

The nucleotides are put together during DEHYDRATION SYNTHESIS reactions.

Draw this nucleotide in your notes!!

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

Double Helix

o DNA looks like a twisted ladder. It is composed of two strands of nucleotides bonded together.

oThe sides of the ladder are made of alternating sugars and phosphates.

o The “rungs” of the ladder are made of nitrogen bases.

Objectives: Describe the overall structure of DNA

The Double Helix

Objectives: Describe the overall structure of DNA

How do we know about DNA’s shape?

• The double helix is the model proposed by scientists James Watson and Francis Crick in 1953. 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

Bonding Patternso The sugar-phosphate backbone is held together with strong covalent bonds.o The nitrogen bases are held together by weak hydrogen bonds.o The nitrogen bases bond in specific ways according to the Complementary

Base Pairing Rule.o A & T will only bond together. They form 2 H bonds.o C & G will only bond together. They form 3 H bonds.

o The sequence of bases on one strand, will complement the sequence of bases on the other.

So ALWAYS REMEMBER…

1. Adenine ALWAYS 1. Adenine ALWAYS bonds with Thyminebonds with Thymine

A-TA-T

2. Cytosine ALWAYS 2. Cytosine ALWAYS bonds with Guaninebonds with Guanine

C-GC-G

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

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