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NCEA Level 3 Biology (90715) 2011 — page 1 of 3
Assessment Schedule – 2011
Biology: Describe the role of DNA in relation to gene expression (90715)
Assessment Criteria
QUESTION ONE
Achievement
Achievement with Merit
Any TWO of:
• Describes the purpose of DNA
replication.
Eg: Produces an exact copy of the
original DNA before cell division.
Any TWO of:
• Explains the purpose of DNA
replication.
Eg: Produces a copy of the original
DNA before cell division / new cells
formed (from mitosis) have an exact
copy, with same instructions
(information) / structure / function.
• Enzymes are named.
A = helicase
B = DNA polymerase (iii)
C = DNA ligase.
• Describes role of enzymes.
Eg: Helicase unwinds the DNA helix
DNA polymerase iii joins new
nucleotides to DNA strand
DNA ligase joins short strands /
Okazaki fragments of DNA together
(at the backbone).
• Explains role of three enzymes in
replication.
Eg: Helicase unwinds the DNA helix
into single (template) strands by
breaking the H bonds between base
pairs.
DNA polymerase iii joins new
nucleotides onto the 3’ end of the
newly forming replicated DNA
strand / DNA polymerase can only
synthesize in the 5’ to 3’ direction,
DNA ligase joins short strands /
Okazaki fragments of DNA together
/ forming phosphodiester bonds /
sugar phosphate backbone.
• Explains consequences of any
enzyme failure in replication.
Eg: If Helicase fails to unwind the
DNA, the bases will not be exposed
for base pairing, so replication will
not happen.
Achievement with Excellence
Discusses role of three enzymes.
Eg: Helicase unwinds the DNA helix
into single strands by breaking the H
bonds between base pairs.
DNA polymerase iii joins new
nucleotides onto the 3’ end of the
newly forming replicated DNA strand
/ DNA polymerase can only synthesize
in the 5’ to 3’ direction.
DNA ligase joins Okazaki fragments
of DNA together / forming
phosphodiester bonds / sugar
phosphate backbone.
AND
Discusses consequence of enzyme
failures in replication.
Eg: DNA polymerase iii fails to attach
to the DNA or attaches an incorrect
matching base (A-C instead of A-T).
This results in a mutation.
NCEA Level 3 Biology (90715) 2011 — page 2 of 3
QUESTION TWO
Achievement
Achievement with Merit
Achievement with Excellence
Any TWO of:
• Transcription is described.
Eg: Production of mRNA copy of
DNA / genetic material
Any TWO of:
• Explains the roles of transcription.
Eg: Transcription is the process
where mRNA is manufactured by
attaching free nucleotides to
complementary DNA strand.
Discusses how DNA sequence results
in the formation of a protein.
• Translation is described.
E.g. information from mRNA is used
to join amino acids into a polypeptide.
• A role of RNA is described.
Eg: mRNA carries the code from a
gene to / site of synthesis / ribosome.
Eg: tRNA carries an amino acid which
connects with the codon of mRNA at
the ribosome.
• Explains the role of translation.
Eg: Translation is the process
happening at the ribosome, where
RNA codons are matched with
tRNA anti codons, resulting in the
joining of amino acids.
Each amino acid is specific to an
anticodon / codon.
• Explains a link between amino acids
and protein folding
Eg: The interactions between amino
acids sequence can affect the final
shape / folding of the protein.
Eg: During transcription, mRNA is
produced through complementary base
pairing with exposed bases on DNA.
mRNA is read via translation at the
site of the ribosome (rRNA), where
codon sequences are translated via
tRNA into a chain of amino acids.
tRNA attach to specific amino acids
and contain an anti codon,
complementary to the codons of the
mRNA.
AND
The final protein / order in which the
amino acids are joined is a result of the
DNA sequence / genetic code.
OR
The order of amino acids affects the
folding of the protein structure due to
the interactions between them. Sulfur
bridges / bonds between cysteines /
hydrophobic / hydrophilic interactions
/ will lead to folding of the polypeptide
/ protein chain.
NCEA Level 3 Biology (90715) 2011 — page 3 of 3
QUESTION THREE
Achievement
Achievement with Merit
Achievement with Excellence
Any TWO of:
• Describes linkage
Linked genes are carried on the same
chromosome.
Any TWO of:
• Explains by comparing observed
outcome with expected outcome.
Eg: If genes are not linked, will get
9:3:3:1, but observed outcome is
different (12:1:1:2). Observed
creates extra parental phenotypes
(purple-long and red-round).
Discusses the linkage cross in terms
of the observed results,
• Explains linkage cross
Eg Genes P and L / p and l are on
the same chromosome so are
inherited together so we get a 3: 1
ratio.
AND
• Describes expected or observed
outcome.
Eg: Expected 9:3:3:1, but in the
observed there were extra parental
phenotypes / purple long /
OR
Eg: 12:1:1:2 observed results
produced extra parental phenotypes /
purple long than expected.
• Describes linkage cross
Crossing over / recombination is the
source of Purple round / red long
offspring
OR
expected outcome from cross is 3
Purple long: 1 red round.
• Explains appearance of
recombinants.
Crossing over separates P and L
(purple and long) and p and l (red
and round) in a few cases. This
makes the other 2 phenotypes
possible.
Eg: Linked genes are on the same
chromosome, therefore they will not
sort independently (separate) during
meiosis and will be inherited together
(giving a 3 (purple long):1(red round)
ratio).
The observed results show a result like
this, but there are small numbers of
recombinants (Pl 5% and pL 5%).
These outcomes are due to
(recombination) crossing over.
Evidence can be taken from a diagram.
Eg:
PL PL
pl PL
!
!becomes!
!
pl pl
pL pl
(It is the new Pl and pL chromosomes
that give rise to the recombinants.)
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2A
OR
1M+1A
2M
OR
1E+1M
2E