Welcome to the DNA 1 debriefing.

Type your answers in the spaces provided. Click on the Check buttons when you have completed each question.


1. DNA is a polymer, a chain of similar subunits (monomers) linked together in a consistent way. The monomers are called nucleotides. What are the parts of a nucleotide?

Correct! The backbone of DNA is formed by the deoxyribose ring and the phosphate groups. Each ribose binds a base by a glycosidic bond to the 1' carbon.
That is not one of the components of DNA. Try again.
You have entered a component more than once. Which part of DNA are you missing?

2. Because of the way bases pair in DNA, there are definite relationships between their mole percentages. If the mole % of G in a DNA molecule is 24%, what is the mole % of C? of A+T?

Mole percent of C = % Mole percent of A + T = %
Correct! Since G always pairs with C, their mole percents must be equal. The sum of the mole percents of all four bases must be equal to 100%.
If G always pairs with C, what is the relation between their mole percents?
What has to be the sum of all four mole percents?

One of the most powerful techniques in molecular biology is the ability to introduce changes, or mutations, at specific points in DNA. This technique is called site-directed mutagenesis. Site-directed mutagenesis needs a piece of DNA complementary to the target sequence everywhere but at the actual site, where the complement of the desired nucleotide is used instead. For example, if the T in 5'-CTG-3' needs to be changed to G, the piece of DNA needed would be 5'-CCG-3' (since complementary strands have the opposite 5' to 3' orientation).

3. In the following sequence of DNA, if the A in the 4th position is to be mutated to G, what should the sequence of the complementary strand be?

TCGATTC

Correct! To change the A in the fourth position to G, the complementary strand must have a C in the fourth position. DNA sequences are written in the 5' to 3' direction.

Remember to give the correct 5' to 3' orientation.
Remember that A pairs with T and G pairs with C.

Congratulations!

You have completed the DNA 1 module.

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