DNA Exam Questions Flashcards
(20 cards)
Describe the chemical reactions involved in the conversion of polymers to monomers and
monomers to polymers.
Give two named examples of polymers and their associated monomers to illustrate your
answer.
Condensation reaction is where 2 molecules join together forming a chemical bond releasing water
A hydrolysis reaction is breaking a chemical bond between 2 molecules using water
Polymers are formed from many monomers joined together
Nucleotides + Polynucleotide-> DNA+ RNA
Alpha glucose -> Starch + Glycogen
Amino acids and polypeptide -> enzymes, protein
Describe the process of semi-conservative replication of DNA.
DNA helicase breaks hydrogen bonds between the complementary base pairs. Also unwinds the double helix
Exposed templates act as a strand
Free DNA nucleotides line up in complementary pairs A-T + C-G
DNA polymerase joins adjacent nucleotides via condensaton reaction by ATP
Also catalyses the formation of phosphodiester bonds/forms phosphodiester bonds
Each new DNA molecule consists of one old strand
Name the type of bond between:
complementary base pairs
adjacent nucleotides in a DNA strand
- hydrogen
- phosphodiester
The length of a gene is described as the number of nucleotide base pairs it
contains.
Use information in above diagram to calculate the length of a gene
containing 4.38 × 103 base pairs.
1861
The generation time for a population of bacteria is the time taken for all the bacteria to divide once by binary fission.
Use Figure 1 and the following equation to calculate the generation time
for this population of bacteria. Give your answer in hours
0.84
describe the structure of DNA.
contains hydrogen bonds between complementary base pairs A-T, C-G
contains bases adenine, cyostine and thymine and guanine
nucleotide made up 1 phosphate group a deoxyribose and a nitogenous containing group (adenine)
polynucleotide
double helix 2 strands
phosphodiester bonds between adjacent nucleotides
Describe how a phosphodiester bond is formed between two nucleotides
within a DNA molecule.
condensation reaction between deoxyribose and phosphate group
RNA polymerase catalyses the formation of phosphodiester bonds
The two DNA strands of a particular gene contain 168 guanine bases
between them. The relationship between the numbers of guanine bases
(G), adenine bases (A), thymine bases (T) and cytosine bases (C) in these
two strands of DNA is shown in the following equation.
G = 4(A + T) – C
Use this information and your understanding of DNA structure to calculate
the maximum number of amino acids coded by this gene
70
420 total bases in gene
Name the protein associated with DNA in a chromosome.
Histone
In the process of semi-conservative DNA replication, the two strands within
a DNA molecule are separated. Each then acts as a template for the
formation of a new complementary strand.
Describe how the separation of strands occurs.
DNA helicase breaks hydrogen bonds between complementary base pairs exposing 2 template strands
describe the role of DNA polymerase in the semi-conservative replication
of DNA.
joins adjacent DNA nucleotides together via condensation reaction
catalyses the formation of phosphodiester bonds
A scientist replicated DNA in a test tube. To do this, he mixed an enzyme with
identical single-stranded DNA fragments and a solution containing DNA
nucleotides.
Name the enzyme used
DNA polymerase
the role of the DNA nucleotides.
Forms complementary pairs / A – T, G - C
OR
Forms complementary (DNA) strand;
Give two features of DNA and explain how each one is important in the
semi-conservative replication of DNA.
weak hydrogen bonds which can be easily broken by DNA helicase
2 strands so both can act as template
complementary base pairs ensure accurate replication
Replication of mitochondrial DNA (mtDNA) is different from that of nuclear
DNA.
The replication of the second strand of mtDNA only starts after two-thirds
of the first strand of mtDNA has been copied.
A piece of mtDNA is 16 500 base pairs long and is replicated at a rate of
50 nucleotides per second.
Tick (✓) the box that shows how long it would take to copy this mtDNA
220
330
440
550
550
Describe the role of two named enzymes in the process of semi
conservative replication of DNA.
DNA helicase breaks hydrogen bonds between the complementary base pairs
DNA polymerase joins adjacent nucleotides via condensation reaction
also catalyses formation of phosphodiester bonds
Scientists investigated the function of a eukaryotic cell protein called cyclin
A. This protein is thought to be involved with the binding of one of the
enzymes required at the start of DNA replication.
The scientists treated cultures of cells in the following ways.
C – Control cells, untreated
D – Added antibody that binds specifically to cyclin A
E – Added RNA that prevents translation of cyclin A
F – Added RNA that prevents translation of cyclin A and added cyclin A
protein
explain the results in the pattern
Treatment D Antibody binds to cyclin A so) it cannot bind to
DNA/enzyme/initiate DNA replication;
For ‘bind to enzyme’ accept ‘activate’.
Idea of ‘initiate DNA replication’ must be linked to
start not just less replication.
For ‘enzyme’ accept named enzyme.
(Treatment E) RNA interferes with mRNA/tRNA/ribosome/polypeptide
formation (so cyclin A not made);
In Treatment F added cyclin A can bind to DNA/enzyme (to initiate
DNA replication)
OR
Treatment F shows that it is the cyclin A that is being affected in the
other treatments
OR
Treatment F shows that cyclin A allows the enzyme to bind (to DNA)
OR
(Some cells in D or E) can continue with DNA replication because
they have a different cyclin A allele
OR
(Some cells in D or E) can continue with DNA replication because the
antibody/RNA has not bound to all the cyclin A protein/mRNA
OR
(Some cells in E) can continue with DNA replication because they
contain previously translated cyclin A;
Contrast the structures of ATP and a nucleotide found in DNA to give two
differences.
ATP has ribose sugar DNA has deoxyribose
Has 3 phosphate groups DNA has 1
Use Figure 1, Figure 2 and your knowledge of enzyme action to explain
why the arrows point in opposite directions.
(Figure 1 shows) DNA has antiparallel strands / described;
(Figure 1 shows) shape of the nucleotides is different /
nucleotides aligned differently;
Enzymes have active sites with specific shape;
Only substrates with complementary shape / only the 3’ end
can bind with active site of enzyme / active site of DNA
polymerase.
During replication, the two DNA strands separate and each acts as a
template for the production of a new strand. As new DNA strands are
produced, nucleotides can only be added in the 5’ to 3’ direction.
Use the figure in part (a) and your knowledge of enzyme action and DNA
replication to explain why new nucleotides can only be added in a 5’ to 3’
direction.
Reference to DNA polymerase;
Which is) specific;
Only complementary with / binds to 5’ end (of strand);
Reject hydrogen bonds / base pairing
Shapes of 5’ end and 3’ end are different / description of how
different.
