DNA Structure and Function Chapter 13. DNA Deoxyribonucleic Acid.
DNA Structure A review. DNA Structure DNA (deoxyribonucleic acid) is a polymer of nucleotides What...
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Transcript of DNA Structure A review. DNA Structure DNA (deoxyribonucleic acid) is a polymer of nucleotides What...
DNA Structure
A review
DNA Structure DNA (deoxyribonucleic acid) is a polymer
of nucleotides What are the 3 parts of a nucleotide?
a nitrogen basea pentose sugara phosphate group
DNA Structure Copy Figure 1 in your notes (on page 210)
DNA Structure What are the four bases?
AdenineThymineGuanineCytosine
Complete the chart and align the bases that pair up
Purines Pyrimidines
This type of pairing is called complementary base pairing
Why do the bases pair this way? Franklin and Wilkins studies show that DNA has
a constant diameter of 2nm If two purines bonded together, DNA would be
wider at some points (the same goes for two pyrimidines bonded)
What holds purines & pyrimidines together? These can only form in the A-T and G-C
arrangement This is the glue that holds the molecule together
and any other pairing would result in instability
G-C pair results in 3 Hydrogen
Bonds
A-T pair results in 2 Hydrogen
Bonds
Which pair is stronger (harder to pull apart)?
DNA Structure
What do purines have in common?six-membered ring joined to a five-membered
ring
What do pyrimidines have in common?single six-membered ring
Create an equation for the amount of A vs. T and G vs. C. Then, create a formula that shows the amounts of purines versus pyrimidines.
If a sample of DNA has 40% G, how much A, C, and T must there be?
Draw Figure 3 in your notes. Label the carbons 1’ to 5’.
DNA consists of two antiparallel strands, curled around in a double helix (like a spiral).
Antiparallel?Huh?• If one strand is going in a 3’ to 5’ direction, the other is oriented in a 5’ to 3’ direction
• i.e.
• How do you know which one is the 5’ end? 3’ end?
Activity Find a partner As a class, form two lines so that each partner
faces each other Now turn so that ne line looks toward the right
side of the room The other line look toward the left side of the
room Put your left hand on the shoulder of the person
standing in front of you Hold your right hand with your original partner
Activity Questions What does your torso represent? What does your left elbow represent? What does your left arm represent? What does your right hand represent? What type of interaction holds the two lines together? Have one partner choose a base Decide what base the other partner must be and
determine how many bonds form between you (3 or 2 fingers)
Where are the 5’ and 3’ ends of each strand? What would happen if two purines were together? What arrangement of bases would be easiest to
separate? Why would this be helpful?
Properties of DNA
3.4 nm
Properties of DNA The diameter of DNA is 2.0 nm Right handed helix (turns clockwise) There is one complete turn for every 10
nucleotides in 3.4 nm (billionth of a m)How many nm does each nucleotide take up?
Bases are stacked on top of each other Sugar-phosphate backbone + hydrogen
bonds between complementary bases make the double helix very stable
Sequence of Bases hold Genetic Information If you know the sequence of one strand, you can
determine the sequence of the second strand One strand can be used as a template to build a
new strand 5’ – ACGCGTTATCGA – 3’
What’s the sequence of the other? Direction?
What would be free at the 5’ end? 3’ end?
Do a little research…! What is the role of the Canadian Food Inspection Agency
with respect to biotechnology? What role does the Canadian Environmental Protection Act
play in regulating biotechnology? Why was bovine growth hormone approved for use in dairy
cattle in the United States but not in Canada? Why does Mexico have laws to limit the cultivation of
genetically modified corn? What countries have banned human cloning? What is
Canada’s position on this issue?