DNA structure- lqc 4a

Question 1

Structure of a mononucleotide

Answer 1

The pentose sugar in a DNA mononucleotide is always deoxyribose. The one organic base in a DNA mononucleotide could be adenine, guanine, cytosine, or thymine. Nitrogen is found in the base of a mononucleotide.

Question 2

Structure of DNA

Answer 2

DNA mononucleotides are joined together by phosphodiester bonds in
condensation reactions, to form two long polynucleotide chains (DNA strands). The two DNA strands twist around each other forming a double helix and are joined by hydrogen bonds between bases, which hold the two DNA strands
together. DNA is a nucleic acid.

Question 3

adenine always pairs with

Answer 3

thymine

Question 4

number of hydrogen bonds between adenine and thymine

Answer 4

2

Question 5

cytosine always pairs with

Answer 5

guanine

Question 6

number of hydrogen bonds between cytosine and guanine

Answer 6

3

Question 7

Why is complementary base pairing important?

Answer 7

• The bases pair up so there are 3 rings forming each ‘rung’ of the DNA – uniform width between DNA strands
• So hydrogen bonds between bases can form to hold the 2 DNA strands together, forming the double helix

Question 8

What is the function of the hydrogen bonding in DNA?

Answer 8

To hold the two DNA strands together, forming the double helix