The Structure of:. By the end of the day, you should: Know what DNA stands for Understand the shape of DNA and be able to label all parts Know.

DNAThe Structure of:

Objectives:

By the end of the day, you should: Know what DNA stands for Understand the shape of DNA and

be able to label all parts Know the pairs of nucleotides Know how DNA is used

What is DNA?

DNA is the molecule that carries genetic information

So what does that really mean?

“DNA”

DNA stands for deoxyribonucleic acid

We’ll come back to this one…

The Shape

The shape of the DNA molecule is called a double helix Think of DNA’s shape as a ladder that

has been twisted

Straight TwistedLadder Ladder

A Closer Look

It’s nice to think of DNA looking nice and simple

like this:

A Closer Look

But, it really looks more like this:

Let’s break it down…

The “Sides”

Each side of the ladder is called a sugar-phosphate backbone

this part

The “Sides”

The sugar-phosphate backbone…up close Consists of:▪ Phosphate group▪ Deoxyribose sugar

group

The “Rungs”

The rungs of the latter are made up of nitrogenous bases Bonded to the sugar group There are 4 different kinds of

bases in DNA…

The BasesPu

rine

sPy

rim

idin

es

Nucleotide

A deoxyribose sugar group and a phosphate group and a nitrogenous base make up a nucleotide

P

P

P

P

Adenine

Guanine

Cytosine

Thymine

Putting it Together The deoxyribose sugar group of one nucleotide

bonds to the phosphate group of another nucleotide to form the sugar-phosphate backbone

The nitrogenous bases of one sugar-phosphate backbone bond to the nitrogenous bases of the other sugar-phosphate backbone to make base pairs A only bonds with T G only bonds with C

Putting it Together

Quick Practice: If you had a strand of DNA where one

side had this sequence of bases: ATAGGCAT

What would the other side’s sequence be???

Putting it Together

PA

PA

P

G

PC

PC

P

G

P

T

P

T

Use?

Now that you know about the structure of DNA, let’s revisit its function…

Use?

Short version: DNA stores genetic information

Long version: The sequence (order) of bases on the strand of DNA is a code for a blueprint of hundreds of thousands of different proteins that, when made, make up living things