DNA Structure Notes

• QQ#1:–What do you know about the structure of DNA?

–Be as detailed as Possible

Deoxyribose Nucleic Acid: Structure NotesMicrosoft ClipArt GalleryCalled a double

helix (a spiral ladder)

DNA is a Polymer• DNA’s Monomers: • repeating subunits called NUCLEOTIDES

• Nucleotides consist of three parts:• Phosphate Group• Sugar Group• Nitrogenous Base

QQ#2

What are the three parts of the nucleotide?

Nucleotide Structure

Copy theDiagram In your notes:

• The phosphate bonds to what is called the 5’ (five prime) carbon of the sugar molecule.

• The base bonds with the sugar at the 1’ carbon. – Can be one of four bases:• Adenine, Thymine, Cytosine, Guanine

Discuss: How do you

think these may link

together to form a

polymer?

Nucleotides are repeating Subunits

• QQ#3–Draw a visual to represent two nucleotides bonding together

DNA’s Repeating Structure DNA is directional

The nucleotides are connected together by a phosphodiester bond between phosphate groups at the 3’ and 5’ carbon on the the sugar molecule.

These bonds create one side of the strand of DNA.

The other (complementary) strand runs in the opposite direction connected in the middle by the bases called anti-parallel chain

Bases In general

bases can accept hydrogen ions or more generally, donate a pair of valence electrons when bonding

The opposite of an acid

Categories of Bases pyrimidines – one ring

Cytosine and Thymine purines – two rings

Adenine and Guanine

• QQ#4:–Can you think of a way to remember which bases are purines and which are pyrimidines?

Categories of Bases

pyrimidines – one ring

Cytosine and Thymine

purines – two rings

Adenine and Guanine

Hydrogen Bonds• A Purine always bonds with

a Pyrimidine• Bases are connected across

middle of helix:• Adenine forms (2) h-bonds

with Thymine• Guanine forms (3) h-bonds

with Cytosine• These bonds hold the two

strands of DNA together and cause the twisting to occur

• The entire code that instructs our cells depends on the order of Adenine, Guanine, Thymine, Cytosine

• The specific bonding angles of the nucleotides forces the helix shape.

• Within the helix there is a major and minor groove

Major and Minor Grooves

• Caused by bonding angles

• Major groove allows proteins to bond: important for replication.

• Each full twist of the helix has 10 nucleotides

Putting it All together

http://www.youtube.com/watch?v=ZGHkHMoyC5I

Exit Slip

• On a separate scratch piece of paper, answer the following questions.1. What do you know now about DNA structure?2. Compare this knowledge with what you knew before?3. Why is the structure of DNA important to the essential questions: In what way(s) does your DNA define you?4. Predict how the structure of DNA relates to how all organisms have the same exact DNA in all cells

Your Model

• You may create a model with our without the major and minor grooves. All other components of DNA structure must be included for accuracy