DNA

Question 1

What is the structure of DNA?

Answer 1

• Double helix with 2 polynucleotide chains
• Held together by hydrogen bonds
• Between specific complementary base pairs

Question 2

What does a condensation reaction between 2 nucleotides form?

Answer 2

Polynucleotide
By phosphodiester bonds

Question 3

How are DNA nucleotides joined together?

Answer 3

The phosphate group of one nucleotide is joined to the sugar molecule of the next nucleotide

Question 4

What does the connection of the sugar and phosphate group between 2 DNA nucleotides form?

Answer 4

Sugar-phosphate backbone

Question 5

Why is a DNA molecule shaped as a double helix?

Answer 5

• Due to hydrophobic and hydrophilic interactions between molecules
• Nitrogenous bases: hydrophobic so avoid contact with cell fluids and stay inwards
• Sugar phosphate backbone: Hydrophillic so will remain outwards

Question 6

How does DNA have antiparallel strands?

Answer 6

Starting point of DNA is known as 5’ end (five prime)
Ending point of DNA is known as 3’ end (three prime)
One end runs from 5’ to 3’ and the other end runs from 3’ to 5’

Question 7

Which bases pair together in DNA?

Answer 7

Adenine and thymine
Guanine and cytosine

Question 8

How is DNA organised in eukaryotic cells?

Answer 8

• Packed into chromosomes
• Each consist of a linear DNA molecule
• Coiled around proteins called histones

Question 9

How is DNA organised in prokaryotic cells?

Answer 9

• Composed of a single, double stranded DNA
• Form of a loop or circle
• Region containing DNA is called a nucleoid