2.1 DNA structure

Question 1

What makes up DNA’s structure?

Answer 1

~DNA is a polymer of nucleotides
~The components of a DNA nucleotide are : a deoxyribose sugar, a phosphate group, and one of the nitrogen containing bases ( adenine, guanine, thymine, cytosine)
Nucleotides are joined together by condensation reactions

Question 2

What are purines and pyrimidines?

Answer 2

~ adenine and guanine are purines
~ thymine and cytosine pyrimidines
A purine always pairs with a pyrimidine.

Question 3

What is the bond between nucleotides and how is it formed?

Answer 3

When nucleotides condense together, a phosphodiester bond is formed, it is formed between the OH on C3 of the deoxyribose sugar and on the phosphate group of the C5 on the adjacent nucleotide.


Question 4

Describe the structure of DNA

Answer 4

~DNA is made up of two strands of nucleotides held together by hydrogen bonds
~ DNA is antiparallel as the deoxyribose sugar and phosphate molecules alternate to form ‘uprights’ and the organic bases together to form the rungs

Question 5

Explain how DNA has a double helix structure

Answer 5

~ polynucleotide chains are twisted together to form a ladder like arrangement 
~ the uprights of phosphate and deoxyribose wind around one another to form the structural backbone of the DNA molecule

Question 6

What makes DNA a stable molecule?

Answer 6

~ phosphodiester back bone protects the chemically reactive bases inside the double helix
~ the hydrogen bonds form bridges between the phosphodiester uprights -the hydrogen bonds make the DNA molecule more stable

Question 7

How is a DNA molecule adapted to its function?

Answer 7

~ DNA is a large molecule so it can store a lot of genetic info
~ the complimentary base pairing means that DNA can easily be replicated
~ separate strands of join together by hydrogen bonds, so they can separate for replication and protein synthesis
~ mutations are rare as the structure passes down generations without change