BIOC0001 MEGA SET EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Polymer
a molecular structure formed by a large number of similar units (monomers)
Polymerisation
chemical process of linking two or more monomers
Monomers of DNA?
CATG
Monomers of RNA?
CAUG
What components make up a nucleotide?
-Pentose sugar
-Cyclic nitrogenous base
-Phosphate groups
What are the pyrimidines?
single ringed structures-C, T, U
What are the purines?
doubles ringed structures- A and G
Why is ' used in carbon positions on pentose sugar?
To distinguish them from the carbon positions on the nitrogenous bases (which are
denoted by counting clockwise)
,What are ribonucleosides?
A ribose sugar and a nitrogenous base.
What group is on the C-2' of a ribose sugar?
Hydroxyl group
What bond links the base to sugar in nucleosides?
A beta-N-glycosidic bond
What is the main difference between deoxy/ribonucleosides?
Deoxyribonucleosides have a hydrogen group on the C-2'
List all of the ribonucleosides.
Adenosine, Cytidine, Uridine, Guanosine
List all of the deoxyribonucleosides.
Deoxyadenosine, deoxycytidine, deoxythymidine, deoxyguanosine
What are the components of a nucleotide?
base, sugar, phosphate
List the DNA nucleotides.
dAMP, dCMP, dGMP and dTMP
What is the 5' end of a polynucleotide?
The nucleotide with a free 5' phosphoryl group
What is the 3' end of a polynucleotide?
The nucleotide with a free 3'- hydroxyl group
What are nucleases?
enzyme which cleave ester bonds in DNA or RNA and can generate different products.
What do exonucleases do?
,Act on one free end of the polynucleotide and cleave the next phosphodiester linkage
What do endonucleases do?
Cleave internal phosphodiester linkages.
What is Chargaff's rule?
Ratio of purines to pyrimidines is always 1. Base pairing is A=T and C=G to maintain
geometry
What is B-form DNA?
Most common form of DNA found in long strands (right-handed)
Statistics about B-form DNA?
Pitch: 3.5nm
Rise: 0.34nm
What is the 'rise' of DNA?
distance between one base pair and the next along the helical axis
What is the 'pitch' of DNA?
the distance to complete one turn
What is A form DNA?
Found when DNA is dehydrated, is also a right-handed helix but is more tightly wound
What is Z form DNA?
Found when certain GC rich sequences are present, is left-handed and has no grooves
Why does DNA need to be packaged efficiently?
If not the cell would need to be 2m in diameter to contain all of the base pairs
How is DNA packaged efficiently?
, DNA associates with histones which coil like beads on a string, these form layers and
then arrange into a scaffold which coils and condenses forming chromosomes
What is semiconservative replication?
Each new helix contains a strand from the parent DNA molecule and a newly
synthesized strand.
What does bidirectional mean?
Growth of both strands from one origin using two replication forks
What is the 'replication bubble'?
Another term for the origin- it gets larger as time proceeds
How long does it take E. Coli to replicate their circular chromosome?
42 minutes
What is rate of fork movement in E. Coli?
920bp/second
What is a 9-mer or 13-mer?
Regions of nucleotide repeats
How many regions of 9 and 13-mers are there?
5 and 3
First stage in DNA unwinding?
DNAa recognises the regions of 9-mers which it binds to causing DNA to coil around the
protein. 13-mers left exposed
Second stage in DNA unwinding?
Energy from ATP allows unwinding at 13-mer regions
Third stage in DNA unwinding?
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Polymer
a molecular structure formed by a large number of similar units (monomers)
Polymerisation
chemical process of linking two or more monomers
Monomers of DNA?
CATG
Monomers of RNA?
CAUG
What components make up a nucleotide?
-Pentose sugar
-Cyclic nitrogenous base
-Phosphate groups
What are the pyrimidines?
single ringed structures-C, T, U
What are the purines?
doubles ringed structures- A and G
Why is ' used in carbon positions on pentose sugar?
To distinguish them from the carbon positions on the nitrogenous bases (which are
denoted by counting clockwise)
,What are ribonucleosides?
A ribose sugar and a nitrogenous base.
What group is on the C-2' of a ribose sugar?
Hydroxyl group
What bond links the base to sugar in nucleosides?
A beta-N-glycosidic bond
What is the main difference between deoxy/ribonucleosides?
Deoxyribonucleosides have a hydrogen group on the C-2'
List all of the ribonucleosides.
Adenosine, Cytidine, Uridine, Guanosine
List all of the deoxyribonucleosides.
Deoxyadenosine, deoxycytidine, deoxythymidine, deoxyguanosine
What are the components of a nucleotide?
base, sugar, phosphate
List the DNA nucleotides.
dAMP, dCMP, dGMP and dTMP
What is the 5' end of a polynucleotide?
The nucleotide with a free 5' phosphoryl group
What is the 3' end of a polynucleotide?
The nucleotide with a free 3'- hydroxyl group
What are nucleases?
enzyme which cleave ester bonds in DNA or RNA and can generate different products.
What do exonucleases do?
,Act on one free end of the polynucleotide and cleave the next phosphodiester linkage
What do endonucleases do?
Cleave internal phosphodiester linkages.
What is Chargaff's rule?
Ratio of purines to pyrimidines is always 1. Base pairing is A=T and C=G to maintain
geometry
What is B-form DNA?
Most common form of DNA found in long strands (right-handed)
Statistics about B-form DNA?
Pitch: 3.5nm
Rise: 0.34nm
What is the 'rise' of DNA?
distance between one base pair and the next along the helical axis
What is the 'pitch' of DNA?
the distance to complete one turn
What is A form DNA?
Found when DNA is dehydrated, is also a right-handed helix but is more tightly wound
What is Z form DNA?
Found when certain GC rich sequences are present, is left-handed and has no grooves
Why does DNA need to be packaged efficiently?
If not the cell would need to be 2m in diameter to contain all of the base pairs
How is DNA packaged efficiently?
, DNA associates with histones which coil like beads on a string, these form layers and
then arrange into a scaffold which coils and condenses forming chromosomes
What is semiconservative replication?
Each new helix contains a strand from the parent DNA molecule and a newly
synthesized strand.
What does bidirectional mean?
Growth of both strands from one origin using two replication forks
What is the 'replication bubble'?
Another term for the origin- it gets larger as time proceeds
How long does it take E. Coli to replicate their circular chromosome?
42 minutes
What is rate of fork movement in E. Coli?
920bp/second
What is a 9-mer or 13-mer?
Regions of nucleotide repeats
How many regions of 9 and 13-mers are there?
5 and 3
First stage in DNA unwinding?
DNAa recognises the regions of 9-mers which it binds to causing DNA to coil around the
protein. 13-mers left exposed
Second stage in DNA unwinding?
Energy from ATP allows unwinding at 13-mer regions
Third stage in DNA unwinding?
