Nucleic Acid Structure and DNA - Lecture 5

Question 1

What is Translation?

Answer 1

Conversion from DNA to messenger RNA

Question 2

What is Transcription?

Answer 2

Conversion of RNA to Protein

Question 3

What is a Nucleoside?

Answer 3

It is a Nucleotide without the Phosphate group

Consists of Base and Sugar

Question 4

What is a Nucleotide composed of?

Answer 4

Phosphate
Sugar
Nitrogenous Base

Question 5

What is the sugar used in DNA?

Answer 5

Deoxyribose

Question 6

What is the sugar used in RNA?

Answer 6

Ribose

Question 7

What are the Purines?

Answer 7

Adenine

Guanine

Question 8

What are the Pyrimidines?

Answer 8

Uracil
Thyamine
Cytosine

Question 9

How is a ncleotide added into a chain?

Answer 9

Hydrogen bond first forms between bases

phosphodiester bond occurs between a free 3’ OH group and a 5’ Triphosphate

Phosphdiester bond causes a loss of 2 Phosphates

Question 10

What is the 5’ end of DNA?

Strand from 5’ to 3’

Answer 10

It is the end of DNA that begins with an OH group on the 3’rd carbon

Ends with Phosphate group on the 5’th carbon

Question 11

What is the 3’ end of DNA?

Strand from 3’ to 5’

Answer 11

It is the end of DNA that starts with the phosphate group on 5’th carbon

Ends with the OH group on the 3’rd carbon

Question 12

What is the “Central Dogma” of DNA?

Answer 12

DNA in each cell constitutes the genome which carries the genetic information required for making an
organism

Question 13

Describe the DNA double helix

Answer 13

One 5' to 3' 
On to 3' to 5' 
They are anitparallel strands
A with T
G with C

Question 14

How many hydrogen bonds are there between Adenine and Thyamine?

Answer 14

Two Hydrogen Bonds

Question 15

How many hydrogen bonds are there between Cytosine and Guanine?

Answer 15

Three Hydrogen Bonds

Question 16

What direct can nucleotides only be added?

Answer 16

Only added from the 3’ end

Question 17

What catalyses DNA replication?

Answer 17

DNA polymerase

Question 18

How does DNA Polymerase operate?

Answer 18

Can only add to existing nucleic acids
Can not start DNA synthesis on their own
Requires an RNA primer to start replication.

Question 19

How does Replication of DNA begin?

Answer 19

DNA helicase binds and unwinds the DNA

Question 20

What are the two strands in DNA termed?

Answer 20

Leading Strand

Lagging Strand

Question 21

Which strand in DNA replication is the leading Strand ?

Answer 21

3’ to 5’ strand

Question 22

Which strand in DNA replication is the lagging strand?

Answer 22

5’ to 3’ end

Question 23

How must the lagging strand be replicated?

Answer 23

By use small okazaki fragments

Question 24

Describe the sequence of DNA replication?

Answer 24

DNA helicase unwinds the strands

RNA primers synthesise and bind to the unwound DNA

Nucleotides are added from the 3’ end

DNA polymerase catalyses the reaction

The lagging strand contains RNA sequences from the Okazaki - These are removed post synthesis

DNA polymerase fills in the gaps of the Okazaki fragments

Question 25

How is the RNA primer synthesised?

Answer 25

Via the use of Primase

Question 26

What acts as a proof reader for DNA?

Answer 26

DNA polymerase has 3’ to 5’ exonuclease activity (acts as a proof reader)