GETTING TO KNOW DNA:

Below is one of the molecules that makes up DNA. What functional groups do you see in the

molecule:

0%

79%

11%

11% 1. Hydroxyl

2. Carboxyl

3. Amino

4. Phosphate

Which of the following contains the most variety of essential elements

0%

100%

0%

0%A

C

B

D

1. A

2. B

3. C

4. D

As you know, DNA stands for….

DEOXYRIBONUCLEIC ACID

Functions of DNA

• Control the processes of heredity by which cells and organisms reproduce proteins

Types of Nucleic Acids

1. DNA (deoxyribonucleic acid): double-stranded

2. RNA (ribonucleic acid): single-stranded

Nucleic Acid Structure

• The monomer units of DNA are known as nucleotides

• All nucleotides have three “parts” in common: a. Phosphate

b. Pentose sugar a. (ribose or deoxyribose)

c. Nitrogen base

Deoxyribose Sugar (DNA)

• Has 5 carbons• Carbon atoms are numbered 1', 2', 3', 4',

and 5' • 5'-carbons link to the phosphate groups• 3'-carbons link to the hydroxyl groups

Is DNA a monomer or polymer

79%

21% 1. Monomer

2. Polymer

What does it mean to be a polymer???

What does it mean to be a monomer?

What type of reaction is being shown below?

Cova

lent

Oxi

datio

n

Hyd

roly

sis

Deh

ydra

tion S

ynth

esis

Poly

mer

izatio

n

0%5%

0%

42%

53%

1. Covalent2. Oxidation3. Hydrolysis4. Dehydration Synthesis5. Polymerization

O

O 0

The molecules marked “Y” and “W”:

32%

5%

0%

5%

58% 1. Polymers and monomers

2. Water and polymer

3. Water and monomer

4. Water and water

5. Monomers and polymers

The monomer units of DNA are known as….

NUCLEOTIDES

All nucleotides have three “parts” in common. They all contain….

Sugar= Deoxyribose

Phosphate Group

One of FOUR different NITROGEN BASES

PLEASE UNDERSTAND, A NUCLEOTIDE IS A VERY COMPLEX STRUCTURE. IF WE REPRESENTED ALL OF THE ATOMS, IT

WOULD LOOK LIKE THIS…

Let’s Practice How to Form DNA!

We will use our hands to represent a nucleotide.

SUGAR

PHOSPHATE NITROGEN BASE

The four different Nitrogen Bases for DNA are abbreviated using the following letters….

Adenine

Thymine

Guanine

Cytosine

A

T

G

C

Using your two hands, please show how you think two nucleotides will/should bond together.

Did you put your hands like this???

Time to find out why this is wrong!!!

Adenine and Guanine are larger molecules known as…

PURINES

LOOK! TWO RINGS!!!

b. Purines: combination of a pentagon shaped ring and a hexagon shaped ring

1. Adenine

2. Guanine

THYMINE and CYTOSINE are smaller molecules known as…

PYRIMIDINES

LOOK! Only one ring!!

Nitrogen Base Pairing

• Adenine and Thymine must form two hydrogen bonds to be stable while Guanine and Cytosine must form three– Makes the base pairing system an extremely

simple: the A-T and C-G pairs are the only ones physically possible

Now, when using our hands to represent the nucleotides, we must modify the nitrogen base in order to represent these PURINES and PYRIMIDINES.

How would you represent a large PURINE?

How would you represent a small PYRIMIDINE?

Full Finger

Half Finger

In DNA, a PURINE always bonds with a PYRIMIDINE when forming a “rung” of the DNA ladder.

LOOK! A long finger pairs with a short finger! In other words, a purine pairs with a pyrimidine.

In DNA, Adenine always pairs with Thymine using two hydrogen

bonds.

A T

A AND T AT THE ATOMIC LEVEL

In DNA GUANINE always pairs with CYTOSINE using three hydrogen bonds.

G C

G AND C AT THE ATOMIC LEVEL

THE

ENTIRE

MOLECULE

AT THE

ATOMIC

LEVEL

Time to use your brain and hands in order to review nucleotide structure and type.

USING YOUR HAND, SHOW ME THYMINE

USING YOUR HAND SHOW ME ADENINE

SHOW ME CYTOSINE

SHOW ME HOW CYTOSINE AND THYMINE BOND TO FORM A RUNG ON THE LADDER

THEY DON’T

OK

Now that you recognize nucleotide type and structure, it’s time to start building the polymer

from these monomers.

In order to make a molecule of DNA, you would need to create many rungs to the DNA ladder.

Look. Many Rungs.

Etc…

What part of the nucleotide alternates to form the sides of the DNA ladder?

Etc…

Sugar, Phosphate.

Sugar, Phosphate.

Sugar, Phosphate.

Etc…

What makes up the “RUNGS” of the ladder?

The Nitrogen Bases

Go Ahead!Stack you hand on top of your partners hands building two rungs of the DNA ladder.

Why is this WRONG????

The sides of the DNA ladder “run” in opposite directions. One side is actually flipped and the nucleotides are upside down!

TRY IT!!!

Because the sides of the DNA “run” in opposite directions, DNA is said to be ANTIPARALLEL.

In this DNA molecule, the THUMB part or better known as the PHOSPHATE GROUP, is said to be the 5 prime (5’) end.

5 prime

5 prime

The “hand” or sugar part of the DNA molecule makes up the 3 prime (3’) end of the DNA ladder.

3 Prime

3 Prime

• Direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel.

• Asymmetric ends of DNA strands are called the 5′ (five prime) and 3′ (three prime) ends– 5' end having a

terminal phosphate group– 3' end having a terminal

hydroxyl group

If you link enough nucleotides together, the DNA molecule begins to take on the characteristic shape known as the

Double Helix

Let’s make a candy version of our DNA

You Need…• Two Pipe cleaners

• Two red twizzlers

• Two black twizzlers

• Many toothpicks

• Four different colored marshmallows

The marshmallows represent the nitrogen bases. Let’s decide as a class what colors will represent the following nitrogen bases.

ADENINE=

THYMINE=

CYTOSINE=

GUANINE=

Cut the black twizzlers into 1.5 cm pieces.

These will represent the phosphate groups

Cut the red twizzlers into 3 cm pieces.

These will represent the sugars.

Person One

Person Two

Add the twizzlers to the pipe cleaners.

Remember, you need to alternate SUGAR (red) AND PHOSPHATE GROUPS (black).

When you are finished, your strand should not end in the same color you started with!

Did you and your partner make the same number of nucleotides

on the sides of your ladder?

If not, FIX IT!!!

Time to put together the two sides.

Using the toothpicks and marshmallows, you are to add the nitrogen bases to the sides of the ladder. Remember, the nitrogen bases “come off” the sugar part of the nucleotide. As a result, they should be coming off of the red twizzler.

Please use two of the same color marshmallows to represent one ADENINE and GUANINE. The BIG purines.

Please use only one marshmallow to represent THYMINE and CYTOSINE. The small pyrimidines.

Following your teachers directions, let’s build one

long strand of DNA

What is a GENE?