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Questions
Q1.
Proteins are made up of amino acids.
The table shows the DNA bases that code for some of the amino acids found in proteins.
Part of the DNA coding for a protein is:
(i) State the order of amino acids coded for by this sequence of DNA.
(1)
..............................................................................................................................................
(ii) These amino acids will be joined together during protein synthesis.
During which stage of protein synthesis will this take place?
(1)
..............................................................................................................................................
(iii) Complete the sentence by putting a cross (
) in the box next to your answer.
Amino acids are joined together
(1)
A
B
C
D
at the membrane
in the mitochondria
in the nucleus
at the ribosome
Q2.
Mutations can occur in genes.
Mutations can cause genetic disorders in humans.
Phenylketonuria (PKU) is a genetic disorder caused by a gene mutation.
People with PKU produce an inactive enzyme.
The normal base sequence and the mutated base sequence which can cause PKU are shown below.
normal base sequence ............ C T C G G C C C T............
mutated base sequence ............ C T T G G C C C T............
(i) Describe how the changes that have occurred in the mutated base sequence produce an
inactive enzyme.
(2)
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*(ii) Explain how the mutated base sequence will result in an inactive enzyme being produced during
protein synthesis.
(6)
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Q3.
The diagram shows part of one DNA strand.
(i) Complete the empty boxes to show the mRNA strand coded for by this DNA strand.
(2)
(ii) State the maximum number of amino acids that are coded for by this DNA strand.
(1)
..............................................................................................................................................
Q4.
(i) Fertilisation takes place during sexual reproduction to produce genetically different offspring.
Complete the sentence by putting a cross (
) in the box next to your answer.
Fertilisation occurs when
(1)
A diploid gametes combine to produce a diploid zygote
B diploid gametes combine to produce a haploid zygote
C haploid gametes combine to produce a diploid zygote
D haploid gametes combine to produce a haploid zygote
(ii) Genetically different organisms contain different DNA codes that produce different proteins.
Describe the process that takes place in the nucleus during the first stage of protein synthesis.
(2)
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Q5.
Mutations can occur in DNA.
Describe what effect a mutation could have on the action of an enzyme.
(3)
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Q6.
Proteins are made up of amino acids.
(a) The table shows the DNA bases that code for some of the amino acids found in proteins.
Part of the DNA coding for a protein is:
(i) State the order of amino acids coded for by this sequence of DNA.
(1)
..............................................................................................................................................
(ii) These amino acids will be joined together during protein synthesis.
During which stage of protein synthesis will this take place?
(1)
..............................................................................................................................................
(iii) Complete the sentence by putting a cross (
) in the box next to your answer.
Amino acids are joined together
(1)
A at the membrane
B in the mitochondria
C in the nucleus
D at the ribosome
(b) DNA can code for the amino acids in the active site of an enzyme.
Explain the role of the active site of an enzyme.
(2)
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(c) Mutations can occur in DNA.
Describe what effect a mutation could have on the action of an enzyme.
(3)
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(Total for Question = 8 marks)
Q7.
A short section of DNA from a strawberry is shown in the diagram.
(i) How many codons are shown in this section of DNA?
Put a cross (
) in the box next to your answer.
(1)
A 2
B 3
C 4
D 12
(ii) This DNA is found in a structure within a cell of a strawberry plant.
On the diagram of a plant cell, draw and name the structure containing DNA.
(2)
Q8.
Describe how a section of DNA determines the structure of a protein.
(4)
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Mark Scheme
Q1.
Answer
(i)
met, val, lys met –
val – lys MET VAL
LYS
(ii)
translation
(iii)
D ribosome
Acceptable
answers
Accept mix of upper
and lower case
Accept: metvallys /
metvalys Not
necessary to
separate the words
out.
Accept spellings
such as transation,
transalation reject:
transcription
Mark
(1)
(1)
(1)
Q2.
Question
Number
(i)
Answer
Acceptable answers
Mark
Indicative Content
(2)
Mark
A description
including any two
from the following
points • change in
a base from C to T
(1) • (causes)
change in one
codon/triplet of
bases (1) • results
in a different amino
acid (1)
Question
Number
QWC
(ii)
Level
1
0
1-2
2
3-4
An explanation
linking some of the
following points
• enzymes are
proteins
• mutation in DNA
will result in different
mRNA stran
• during
transcription
• mRNA leaves the
nucleus through the
nuclear pore • the
attachment of mRNA
at the ribosomes
• involvement of
tRNA and amino
acids • at the
ribosome • which
is translation
• amino acid
chain/peptide
sequence altered
• different protein
formed/protein not
(6)
folded correctly
No rewardable material
• an attempt is made to link the change in
the base sequence to the generation of a
different amino acid • the answer
communicates ideas using simple language
and uses limited scientific terminology
• spelling, punctuation and grammar are
used with limited accuracy
• there is evidence that the mutation is
linked to a change in the protein • there
may be an attempt to explain transcription of
the incorrect code and translation of this
although this explanation is likey to be
unclear and may have missing steps • the
answer communicates ideas showing some
3
5-6
evidence of clarity and organisation and
uses scientific terminology appropriately
• spelling, punctuation and grammar are
used with some accuracy
• the response is likely to indicate the type
of mutation and link this to a change of
codon/protein • the response will show
good evidence of understanding that an
incorrect mRNA molecule is formed and
translation by tRNA will result in an incorrect
amino acid being incorporated into the
protein chain • the answer communicates
ideas clearly and coherently uses a range of
scientific terminology accurately • spelling,
punctuation and grammar are used with few
errors
Q3.
Answer
Mark
(i)
(2)
[all correct = 2 marks and 1
mistake = 1 mark]
Answer
(ii)
three / 3
Acceptable
answers
Reject any other
numbers given
Mark
Acceptable
answers
Mark
(1)
Q4.
Answer
(i)
(ii)
C haploid gametes
combine to produce
a diploid zygote
A description
including two of the
following
 transcription (1)
 DNA unzips (1)
 (formation of )
mRNA (1)
 complementary
to / copy of DNA /
DNA acts as a
template (1)
(1)
(2)
Q5.
Answer
A description
including three of
the following points:
 a mutation is a
change in a gene
(sequence) / base
pairs (1)
 (change in DNA)
causes a change in
amino acid(s) /order
of amino acids (1)
 change in shape
of active site / protein
/ enzyme (1)
 prevent / reduce
Acceptable
answers
accept
change enzyme
function / stops the
function of the
enzyme
ignore: refs to
denaturation
Mark
(3)
binding to substrate
(1)
 enzyme can no
longer function /
reduced function (1)
 enzyme could be
more effective (1)
Q6.
Answer
(a)(i)
met, val, lys met –
val – lys MET VAL
LYS
(a)(ii)
translation
(a)(iii)
(b)
(c)
D ribosome
An explanation
including two of the
following points:
 ref to specific
shape (1)
 to bind to
substrate / form
enzyme substrate
complex (1)
 for reaction to
take place /
catalysed(1)
 joining together
substrates /
molecules / break
down substrates /
molecules (1)
 ref to lock and
key mechanism /
hypothesis (1)
A description
including three of
the following points:
 a mutation is a
change in a gene
(sequence) / base
pairs (1)
 (change in DNA)
causes a change in
amino acid(s) /order
of amino acids (1)
 change in shape
of active site / protein
/ enzyme (1)
 prevent / reduce
binding to substrate
(1)
 enzyme can no
longer function /
reduced function (1)
Acceptable
answers
Accept mix of upper
and lower case
Accept: metvallys /
metvalys Not
necessary to
separate the words
out.
Accept spellings
such as transation,
transalation reject:
transcription
Mark
(1)
(1)
(1)
(2)
accept
change enzyme
function / stops the
function of the
enzyme
ignore: refs to
denaturation
(3)
 enzyme could be
more effective (1)
Q7.
Answer
(i)
(ii)
Acceptable
answers
C4
 location drawn
anywhere in
cytoplasm (1)
 correct name nucleus (1)
Mark
(1)
chloroplast /
mitochondria NB
these are stand
alone mark points
(2)
Q8.
Answer
A description
including the
following linked
points
 ref to a gene
(coding for
protein)(1)
 sequence of
bases determines
sequence of amino
acids (1)
 idea of one code
/ triplet / codon / 3
bases (for one amino
acid) (1)
 several amino
acids make up a
protein /
(poly)peptide (1)
 transcription /
detail of transcription
(1)
 translation /
detail of translation
(1)
Acceptable
answers
Mark
Accept on either
DNA or RNA base
pairs
Accept a chain of
amino acids
eg mRNA made
eg mRNA attached
to ribosome
(4)