DNA

Question 1

Why is DNA a polynucleotide ?

Answer 1

It is composed of many nucleotides.

Question 2

What are the main components of DNA.

Answer 2

2 sugar phosphate backbones held together by base pairs.

Question 3

What are the 4 types of nitrogenous base pairs ?

Answer 3

Adenine
Thymine
Guanine
Cytosine

Question 4

Which nitrogenous bases pair together.

Answer 4

A and T

C and G

Question 5

How many hydrogen bonds do each set of nitrogenous bases create ?

Answer 5

A to T = 2 hydrogen bonds

C to G = 3 hydrogen bonds

Question 6

What are the monomers of DNA called.

Answer 6

Nucleotides

Question 7

What are nucleotides.

Answer 7

Monomers of DNA

Question 8

How are nucleotides formed

Answer 8

Condensation reactions where water is removed and replaced by a phosphodiester bond which is created between the sugar and the phosphate in the sugar-phosphate backbone.

Question 9

What is the bond between the ribose sugar and phosphate in DNA called.

Answer 9

Phosphodiester bond

Question 10

What does a phosphodiester bond join ?

Answer 10

Ribose sugar and phosphate

Question 11

Which molecules loose what during the formation of a phosphodiester bond ?

Answer 11

Ribose sugar looses OH

Phosphate looses H

Question 12

What type of bond is created between the sugar and the nitrogenous base in DNA.

Answer 12

Covalent bond

Question 13

Where is a covalent bond created in DNA

Answer 13

Between the sugar and the nitrogenous base.

Question 14

What are the 3 types of bond in DNA and what are they between ?

Answer 14

Hydrogen between nitrogenous bases.
Phosphodiester between sugar and phosphate
Covalent between sugar and base

Question 15

What is the final shape of DNA

Answer 15

Helix due to it twisting

Question 16

Which nitrogenous bases are purines ?

Answer 16

Adenine and guanine

Question 17

Which nitrogenous bases are pyrimidine

Answer 17

Thymine and cytosine

Question 18

What does purine relate to and what does it mean.

Answer 18

Both adenine and guanine nitrogenous bases are purine as they have double ring shapes.

Question 19

What does pyrimidine mean and what does it relate to ?

Answer 19

Both thymine and cytosine and pyrimidine was they have only single ring shapes.

Question 20

Why are DNA strands anti parallel.

Answer 20

The DNA strand are anti parallel as one strand runs from carbon 3 to carbon 5. Whilst the other runs from carbon 5 to carbon 3.

Question 21

What functions of DNA give it the ability to carry out its function ?

Answer 21

Coiling makes it compact
Sugar to phosphate backbone gives strength
Long molecules store a lot of information
Complementary base pairing enables information to be replicated
Double helix protects hydrogen bonds and makes the molecule stronger
Many hydrogen bonds create stability and prevent code corruption
Hydrogen bonding allows chain to split for replication.

Question 22

Describe in detail how DNA is replicated.

Answer 22

1. DNA helicase unwinds the DNA and breaks the hydrogen bonds.
2. The two strands of DNA separate and are stabilised by binding proteins.
3. Free nucleotides approach the exposed bases of both strand. The complementary base pairs form hydrogen bonds.
4. DNA polymerase joins the new nucleotides together by condensation reactions to form a new strand.
5. Each new molecule is an exact copy of the original. With one old parent strand and one newly-synthesised daughter strand.
6. The molecule twists into a helix.
7. This is semi-conservative replication.

Question 23

Why is DNA replication known as semi-conservative ?

Answer 23

When DNA replicated one strand of each molecule is the old parent strand and one is the newly-synthesised daughter strand.

Half remains