DNA double helix

Question 1

What is the double helix made up of?

Answer 1

2 polynucleotide strands coiled into a helix

Question 2

What are the polynucleotide strands held together by?

Answer 2

Hydrogen bonds between bases

Question 3

Why is the double helix antiparallel?

Answer 3

Each strand runs opposite to eachother

E.g. Strand on left has 5’ end (phosphate group) pointing up, whilst strand on right has 5’ end pointing down

5’ end has phosphate group
3’ end has hydroxyl group

Question 4

What are the features of the DNA molecule?

Answer 4

• Has strong sugar-phosphate backbone
• Hydrogen bonds
• Complimentary base pairing
• Stores huge amount of info
• Compact

Question 5

What is the role of the strong sugar-phosphate backbone?

Answer 5

Is held by phosphodiester bonds. When molecule becomes compact, backbone protects weak hydrogen bonds between strands

Question 6

What is the role of hydrogen bonds?

Answer 6

Can be broken by DNA helicase, allowing replication of molecule

Question 7

What is the role of complimentary base pairing?

Answer 7

Ensures that when double helix separates, each strand acts as template strand for synthesis of new strand

Allows for process of transcription

Question 8

Why is it important for the molecule to be able to store lots of info?

Answer 8

Since its a sequence of bases along a strand that codes for diff proteins