Module 2:Nucleotides and Nucleic Acids

Question 1

What does DNA do ?

Answer 1

DNA holds genetic
information

Question 2

What does RNA do ?

Answer 2

RNA transfers genetic information from DNA to the ribosomes

Question 3

Deoxyribonucleic and ribonucleic acid are both what?

Answer 3

polymers of nucleotides

Question 4

What do nucleotides consist of?

Answer 4

-a pentose sugar
-a nitrogenous organic base
-a phosphate group

Question 5

What are the components of a DNA nucleotide?

Answer 5

-deoxyribose
-a phosphate group
-one organic base( A T C G )

Question 6

What are the organic bases ?

Answer 6

adenine , cytosine , guanine , thymine , uracil

Question 7

What are the components of a RNA nucleotide?

Answer 7

-ribose
-a phosphate group
-one organic base( A U C G )

Question 8

How do nucleotides join together?

Answer 8

by phosphodiester bonds formed in condensation reactions

Question 9

What is the structure of DNA?

Answer 9

-its a double helix
-there are 2 polynucleotide chains that are joined together by H bonds between complementary bases

Question 10

What is the structure of RNA?

Answer 10

-its a relatively short single polynucleotide chain

Question 11

What is ATP and what does it consist of ?

Answer 11

-adenosine triphosphate is a nucleotide derivative
-consists of ribose , adenine and three phosphate groups

Question 12

What happens when ATP is hydrolyzed and which enzyme catalyses this reaction?

Answer 12

-energy is released and ATP is broken down into ADP and a phosphate molecule
-ATP hydrolase

Question 13

What can the inorganic phosphate molecule do ?

Answer 13

-it can phosphorylate other compounds and make them more reactive as a result

Question 14

What happens when ADP and the inorganic phosphate undergo a condensation reaction and which enzyme catalyses this reaction?

Answer 14

-produces ATP during photosynthesis and respiration
-catalysed by ATP synthase

Question 15

Why is DNA replication known as semi-conservative?

Answer 15

-because 2 DNA molecules are formed and they each have one original strand and one new strand

Question 16

What does semi-conservative replication ensure?

Answer 16

-it ensures genetic continuity between generations of cells meaning genetic info is passed on from one generation to the next

Question 17

What is the first stage of DNA replication?

Answer 17

-the double helix unwinds and the hydrogen bonds between complementary bases break
-this is catalysed by DNA helicase which runs along the back bone of the strands.
-this separates the two strands

Question 18

What is the second stage of replication

Answer 18

-both strands are used as templates and complementary base pairing occurs between the template strands and free nucleotides in the cytoplasm

Question 19

What is the final stage of DNA replication

Answer 19

adjacent nucleotides are joined by phosphodiester bonds formed in condensation reactions
-this process is catalysed by DNA polymerase

Question 20

What is the genetic code?

What is a triplet known as ?

What does each triplet of bases do?

Answer 20

the order of bases on DNA
-consists of triplets of bases
-a codon

-code for a particular amino acid

Question 21

What type of bonding occurs between amino acids

What do amino acids form?

Answer 21

peptide bonds

long polypeptide chains

Question 22

What is a gene?

Answer 22

a sequence of bases on a DNA molecule coding for a sequence of amino acids in a
polypeptide chain

Question 23

NOT ALL OF THE GENOME CODES FOR PROTEINS

what are the non-coding sections of DNA called?

what are the coding sections called?

Answer 23

Introns

Exons

Question 24

What are the features of the genetic code?

Answer 24

-its NON-OVERLAPPING , meaning each triplet is only read once and triplets don’t share bases

-its DEGENERATE meaning that more than one triplet codes for the same amino acid, this reduces the phenotypic effect of mutations

Question 25

What is meant by a mutation?

Answer 25

when a mistake in the base sequence occurs

Question 26

What else does the genetic code contain?

Answer 26

start and stop codons that control protein synthesis

Question 27

What are the 2 stages of protein synthesis?

Answer 27

transcription
translation

Question 28

Where does transcription occur and what does it involve?

Answer 28

in the nucleus
involves DNA and mRNA
during transcription a molecule of mRNA is made in the nucleus

Question 29

What does translation involve?
(name the 2 molecules , where it happens and what is synthesised

Answer 29

mRNA tRNA and ribosomes
during translation amino acids join together to form a polypeptide chain

Question 30

What is the first two stages of transcription?
What is the name given to the strand that acts as a template?

Answer 30

H bonds between the complementary bases break and the DNA uncoils separating the two strands

One of the DNA strands is used as a template by RNA polymerase to make the
mRNA molecule
the template is called the antisense strand

Question 31

What are the last two stages of transcription?

Answer 31

Free nucleotides line up by complementary base pairing and adjacent nucleotides
are joined by phosphodiester bonds
This forms a single stranded molecule of mRNA

mRNA then moves out of the nucleus through a pore and attaches to a ribosome in
the cytoplasm

Question 32

What are the first two stages of translation?

Answer 32

mRNA attaches to a ribosome and transfer RNA collects amino acids from the
cytoplasm and carries them to the ribosome

tRNA attaches itself to mRNA by complementary base pairing( 2 molecule attach to mRNA at a time)

Question 33

What are the last two stages of translation?

Answer 33

the AA attached to two tRNA molecules join by a peptide bond and the tRNA molecules detach themselves from the AA leaving them behind

the process is repeated which forms a polypeptide chain until a stop codon is reached on mRNA