Nucleic Acids & DNA

Question 1

What are nucleotides?

Answer 1

Monomers that are the building blocks of DNA.

Question 2

What is the basic structure of a nucleotide?

Answer 2

• ribose sugar (joined to…)
• phosphate group
• nitrogenous base

Question 3

What are the 5 different bases?

Answer 3

• Guanine (G)
• Thymine (in DNA) / Uracil (in RNA) (T)
• Adenine (A)
• Cytosine (C)

Question 4

What are purines?

Answer 4

Larger bases with double rings of C and N - cytosine, thymine / uracil.

Question 5

What are pyrimidines?

Answer 5

Smaller bases with single rings of C and N - adenine, guanine.

Question 6

What are DNA and RNA both examples of?

Answer 6

Nucleic acids

• DNA is deoxyribonucleic acid as it’s ribose sugar is dexoyribose.
• RNA is ribonucleic acid as it’s ribose sugar is ribose.

Question 7

What are DNA and RNA?

Answer 7

They are both long chain polymers made up of many individual nucleotides.

Question 8

What are the main other differences between DNA and RNA?

Answer 8

• DNA is a double stranded molecule, RNA is single stranded
• DNA has hydrogen bonding, RNA does not
• DNA has a complementary base pairing, RNA does not

Question 9

How are DNA and RNA chemically different?

Answer 9

Deoxyribose sugar has one less oxygen than ribose sugar. It has a H atom attached to it, where ribose sugar has a hydroxyl (OH).

Question 10

How do nucleotides join?

Answer 10

Nucleotides join via a condensation reaction to form a phosphodiester bond. They are attached between the sugar of one nucleotide and the phosphate of another.

The chain of sugars and phosphates is known as the sugar-phosphate backbone.

Question 11

How are polynucleotides broken back down?

Answer 11

They are broken back into nucleotides by breaking the phosphodiester bonds in a hydrolysis reaction.

Question 12

How does a DNA molecule’s double helix work?

Answer 12

The two strands of the double helix are held together by hydrogen bonds between the bases. Each strand has a phosphate group at one end and a hydroxyl group at the other.

They are arranged so they run in opposite directions and are said to be “antiparallel”.

Question 13

What are the complementary base pairings in DNA?

Answer 13

Adenine and Thymine / Uracil
Cytosine and Guanine

Question 14

Why does adenine form a complementary base pairing with thymine / uracil?

Answer 14

They are both able to form two hydrogen bonds.

Question 15

Why does cytosine form a complementary base pairing with guanine?

Answer 15

They are both able to form three hydrogen bonds.

Question 16

What do complementary base pairings mean?

Answer 16

DNA always has equal amounts of adenine + thymine, and cytosine + guanine.

Small pyrimidine bases always bind to larger purine bases, resulting in parallel polynucleotide chains.

Question 17

How does the structure of DNA relate to it’s function?

Answer 17

• sugar-phosphate backbone - DNA is strong and stable
• many hydrogen bonds - provides strength and stability
• weak hydrogen bonds - strands can be separated during DNA replication
• double stranded - bases are protected and replication can be semi-conservative
• long polymer - can store lots of genetic information
• double helix - compact
• bases in sequence - allows accurate DNA replication