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A deoxyribose sugar A phosphate group
(that is negatively charged)
A nitrogenous base
Adenine Thymine Cytosine Guanine
Adenine and Guanine are grouped as Purines (see diagram pg.210) Purines are a double ring structure
Cytosine and Thymine are Pyrimidines & are a single ring structure
Deoxyribose contain 5 carbon atoms and they are numbered clockwise 1 to 5 beginning with the carbon atom to the immediate right of the oxygen atom.
The first carbon atom is named 1’(1 prime) and so on.
So a nucleotide is a deoxyribose sugar attached to a phosphate group and a nitrogenous base (A, T, G, C)
The phosphate is always attached to the 5’carbon
The nitrogenous base is always attached to the 1’carbon
These repeating units of nucleotides form a simple polymer
DNA Structure Questions Section 4.2 & 4.3 Use the concept of complementary base pairing to explain how if you
know the sequence of one strand of DNA you also know the opposite or complementary strand. Use and example in your explanation.
What keeps the bases together in the middle of the DNA strand? Fully explain how two DNA strands run anti- parallel. Use an example
in your explanation. Which strand is customarily written when writing one strand of DNA?
Why is this? What is the difference between mitosis and cytokinesis? What does it mean when DNA replication is referred to as semi-
conservative? What begins the process of DNA replication? What is the function of DNA helicase?
What keeps the complementary bases apart during DNA replication? What is the function of DNA gyrase? Can DNA be fully unwound? Explain.
DNA polymerase adds nucleotides at a rate of 50 per second in humans. The whole replication of the entire human genome takes 5 to 10 hours.
Enzymes involved in replication
Difference between the Leading Strand & Lagging Strand