Have Your DNA and Eat It Too

I will be able to describe the structure of the DNA moleculeI will be able to explain the rules of base pairingI will understand that information is stored within the DNA molecule in the form of a sequence of chemical bases, (A, T, C, G)

DNA

• Provides the instructions for building and operating ALL living things

– DNA Instructions:• Divided into segments; genes

– Genes:• Provide information to make a protein

– Protein:• Carries out a specific function in the cell

DNA

• Deoxyribonucleic Acid

• Composed of:– 2 backbones– 4 types of chemical bases

Backbone

• Formed by a chain of alternating phosphates and sugars– Sugar molecule• Provides attachment site

for one of the chemical bases

Chemical Bases

• Adenine (A)• Thymine (T)• Cytosine (C)• Guanine (G)

• A pair of bases is connected together by hydrogen bonds– Also connected to a sugar

compound; to attach to the backbone

Base Pair

Base Pair

DNA Molecule• Comparable to a twisted ladder– 2 backbones = sides of ladder– Base pairs = rungs (steps) of ladder– Double helix = twisted ladder shape

• Sequence– Consecutive order of bases on one side

(strand)– Complementary order of bases on other

side (strand)• based on pairing rules• A-T and C-G

DNA ReplicationExact copies of DNA

– Allowed because of the matching of base pairs

1. Double helix untwists2. Two strands separate

– Break hydrogen bonds between base pairs3. Two NEW strands made

– Read each side of the original ladder– One step (base) at a time

4. At each step, matching base fills in (with its matching sugar and phosphate)– Completes the rung– Lengthens the new DNA strand

When process complete: 2 identical DNA double helixes– Each Double Helix:

• One original DNA strand• One New strand

Importance of DNA Replication

• Part of cell division process– Occurs before a cell

divides• Interphase

– Duplicates DNA– New cell will have

SAME genetic information

– Exact copies due to base pair matching

If all organisms have DNA, how are we different?

• Structure of DNA molecules is the SAME in ALL living things

• The diversity of life is the result if differences within the DNA sequence– Different order of A-T and

C-G base pairs (the rungs of the ladder go in a different order!)