NUCLEIC ACIDS

Question 1

What is a nucleotide made of?

Answer 1

Pentose sugar
nitrogenous base
phosphate

Question 2

Name the different nitrogenous bases found in DNA and RNA

Answer 2

Adenine
Guanine
Cytosine
Thymine
Uracil

Question 3

What are the nitrogenous bases divided into? And explain the difference.

Answer 3

Are divided into purines which are double ring structures and pyrimidines which are single ring structures.

Question 4

Which nitrogenous bases are purines?

Answer 4

Adenine and Guanine

Question 5

Which nitrogenous bases are pyrimidines?

Answer 5

Cytosine
Thymine
Uracil

Question 6

Phosphate groups

Answer 6

Attached to the 5-carbon by phosphodiester bonds. The give nucleic acids their acidic nature. Also can attach to any substance making them phosphorylated- activated therefore providing activation energy

Question 7

Describe the structure of the nucleotide of ATP

Answer 7

ATP-Adenosine triphosphate
Sugar - Ribose
Nitrogenous base- Adenine
Three phosphate groups

Question 8

Describe the structure of a DNA nucleotide

Answer 8

DNA-Deoxyribonucleic Acid
Deoxyribose sugar
Nitrogenous bases-A,T,G,C
One phosphate group attached to 5-Carbon

Question 9

Describe the structure of a DNA molecule

Answer 9

There are two polynucleotide chains which run in opposite direction-antiparallel. One strand runs in the 5’-3’ direction while the other runs in the 3’-5’ direction
The two chains precisely coil around each other forming a double helix.
The 5-carbon of one deoxyribose sugar molecule is linked to a phosphate group on the same nucleotide by phosphodiester bonds. The same phosphate group is liked by phosphodiester bonds to the 3-carbon of the deoxyribose sugar on the next nucleotide in a condensation reaction. This forms the sugar phosphate backbone of the chain.
The two antiparallel chains are held by hydrogen bonds between complementary bases.

Question 10

How many hydrogen bonds are there between adenine and thymine?

Answer 10

2

Question 11

How many hydrogen bonds are there between cytosine and guanine?

Answer 11

3

Question 12

Describe the structure of RNA nucleotide

Answer 12

RNA-Ribonucleic acid
Sugar base-Ribose
Nitrogenous bases-A,G,C,U
A phosphate group attached to it

Question 13

Describe the structure of an RNA molecule

Answer 13

One polynucleotide strand made up of alternating ribose sugars and phosphate groups. 5-carbon of one ribose sugar molecule is linked by phosphodiester bonds to a phosphate group which is linked to 3-carbon of the ribose sugar molecule of the next nucleotide by phosphodiester bonds , in a condensation reaction. The sugar phosphate of RNA is formed.

Question 14

State the importance of hydrogen bonding in DNA structure

Answer 14

Hold complementary base pairs together
Provides stability
Can be broken down for transcription or replication

Question 15

Describe the structure of DNA related to its function

Answer 15

Nucleotides are linked by phosphodiester bonds which are very strong covalent bonds. Complementary base pairs are held by hydrogen bonds- this makes DNA very stable. DNA must be stable so that the sequence of amino acids does not change therefore reducing the chances of mutations.
They carry coded information -order of the nucleotide bases can be used to control the production of other molecules
The have specific base pairing so they can be replicated when cells divide. Accurate replication during cell growth and duplication
It is compact due to the folding of the molecule-a great deal of information can be stored in a small volume
A way of transferring information into cell characteristics

Question 16

When does DNA replication occur

Answer 16

s phase of a cell cycle

Question 17

Name the four enzymes needed in DNA replication

Answer 17

DNA helicase
Primase
DNA polymerase
DNA ligase

Question 18

Which parent strand is the leading strand assembled against?

Answer 18

3’ 5’

Question 19

What is a gene?

Answer 19

Length of DNA which codes for a specific polypeptide

Question 20

State the features of the genetic code

Answer 20

Triplet code
Universal
Degenerate
Non-overlapping
Has punctuations

Question 21

What is the codon for START

Answer 21

AUG (Methionine)

Question 22

What are the codons for STOP

Answer 22

UAA
UAG
UGA

Question 23

Name the enzymes required in protein synthesis

Answer 23

RNA polymerase

DNA helicase

Question 24

Describe the structure of a tRNA molecule

Answer 24

One end has three unpaired bases-anticodons

The other end has a site where specific amino acids can bind

Question 25

Describe the structure of a tRNA molecule

Answer 25

One end has three unpaired bases-anticodons

The other end has a site where specific amino acids can bind

Question 26

Types of mutation

Answer 26

Base substitution
Base insertion
Base deletion
Silent mutation

Question 27

What is the effect of base substitution

Answer 27

The altered DNA code causes the mRNA codon to be altered which in turn causes tRNA to bring a different amino acid at translation. Primary structure (sequence of amino acids) is altered therefore the tertiary folding is not correct as the sequence of R groups is changed. The protein can then result to be non functional.

Question 28

Describe the mutation that causes sickle cell anaemia

Answer 28

B-globin chain of haemoglobin is affected. Glutamic acid (CTT) is replaced by Valine (CAT).
Glutamic acid is polar while Valine is non-polar