SBI4U: The Structure of DNA



SBI4U: The Structure of DNA

DNA

• Deoxyribonucleic Acid

• A polymer of many ______________________________

Nucleotides

• Three main components:

1. _________________________

2. _________________________

3. _________________________

• The identity of a nucleotide is determined by its _____________________

2 Types of Nucleotides:

1. Purines: ___________________________________

2. Pyrimidines: ________________________________

***Differences in the sequence of nucleotides are the source of ___________________ between individuals and organisms

Nucleotide Structure:

• Ribose – ________________________

• Carbon naming:

— Clockwise

— Start at C to the right of O

DNA Composition: Chargaff Experiment (1949)

• Chemical analysis:

— Proportion of adenine in DNA is _______________________________

— Proportion of guanine is equal to __________________

— # of ____________ = # of ____________________

DNA Structure

Rosalind Franklin and Maurice Wilkins

• _________________________________________ (imaging technique)

James Watson and Francis Crick

• Used X-ray diffraction pattern ________________________________

• Combined with information from ________________________

• Developed the ____________________ model of DNA

Who got the Nobel Prize in 1962? _______________________________________

Why didn’t Rosalind Franklin get it?

The Double Helix

Two ____________________ strands of nucleotides

• ____________, but running in opposite ___________

• 3`end (_______________)

• 5`end (_______________)

• The two strands wind around each other

o _________________ structure

• Clockwise direction

• One complete turn of the helix :

o ________________

o ________________

• Helix is ______________ in diameter

• _____________________ backbone

• Nitrogenous bases facing in

— Bases are paired with one another:

— _____________________ pairing

*Use Pg. 214 to label a phosphodiester bond, glycosyl bond, and Hydrogen bond on the image above.

Complementary Base Pairing

▪ __________________ bonds

▪ purine + ____________________

▪ A-T (_______________)

▪ G-C (_______________)

▪ this pairing is crucial for the storage

and transfer of genetic information

How do we write a DNA strand?

• Write only the ________strand... why?

▪ Can easily deduce the ______________

___________________________________

Homework: Pg. 216 Q. 1-3, 5-7

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