1.	A
[1]

2.	A
[1]

3.	D
[1]

4.	A
[1]

5.	A
[1]

6.	D
[1]

7.	A
[1]

8.	D
[1]

9.	A
[1]

10.	B
[1]

11.	A
[1]

12.	(a)	(i)	(population) 1 and (population) 2 (both needed)	1
 
(ii)	(population) 11/7/7 and 11	1
 
(b)	PanI^A 0.75 and PanI^B 0.25 / 3 PanI^A to 1 PanI^B	1
Both must be correct for the mark to be awarded, accept
frequencies in form of ratio.
 
(c)	(i)	greatest/great frequencies of PanI^A at lowest/low latitudes /
a rapid drop in frequency at (60–65 degrees latitude) /
lowest/low frequencies at highest/high latitudes	1
Answers which describe/imply the correct step-wise relationship
should get credit. Answers stating or implying a negative
correlation alone should not get credit.
 
(ii)	lowest/low frequencies of PanI^A at lowest/low temperatures /
a rapid increase in frequency at (8–10 degrees Celsius) /
highest/high frequencies at warmest/warm temperatures	1
Answers which describe/imply the correct step-wise relationship
should get credit. Answers stating or implying a negative
correlation alone should not get credit.
 
(d)	(cod with) PanI^A allele selected/favoured/better adapted to warmer water;
(cod with) PanI^B allele selected/favoured/better adapted to colder water;
cod that survive can reproduce and pass alleles on to offspring;	2 max
It takes a whole organism to reproduce in order to pass on the allele,
hence we expect reference to the fish to gain this last marking point.
 
(e)	higher frequency of PanI^A/PanI^A PanI^A (cod) in warm (surface) water;
higher frequency of PanI^B/PanI^B PanI^B (cod) in colder (deeper) water;
interbreeding results in PanI^A PanI^B cod/heterozygous cod;	2 max

(f)	PanI^A PanI^A (cod) may spread further north / PanI^B PanI^B (cod)
may move/retreat further north;
numbers of PanI^A PanI^A (cod) may increase / frequency of PanI^A
allele may increase;
PanI^B PanI^B (cod) may become extinct / frequency of PanI^B allele
may decrease;	2 max
[11]

13.	(a)	(gel) electrophoresis	1
 
(b)	(track C is) not (DNA from) the father;
some bands on track B do not occur on A or C;
these bands must be DNA inherited from the real father;
band in track B that does not occur on A or C identified;
Annotations to the gel illustrating the above points may be used.	3 max
[4]

14.	(a)	drugs used to down-regulate the menstrual cycle;
FSH injected to stimulate many follicles to develop;
HCG injected to cause the follicles to mature;
eggs are harvested/extracted (from the follicles/ovaries);
semen sample produced/collected;
semen is processed to concentrate it / healthy sperm selected
(swim-up test given);
ICSI/IntraCytoplasmic Sperm Injection where sperm is directly
injected into egg when low numbers of motility is a factor;
semen mixed with eggs in a dish/outside the body to allow fertilization;
incubated / kept at 37°C / allows embryos to develop (sufficiently
for implantation);
dish examined to choose healthiest embryo;
embryos placed in uterus/oviduct (using a catheter/long plastic tube);
one/two/three/up to four (in some countries) embryos implanted;
pregnancy test/scan used to see if procedure has been successful;
(used in cases of) blocked oviduct / low sperm count / need for genetic
screening /infertility / cannot become pregnant / need for donor embryo;	9 max
Accept other reasonable situations. Full marks may be awarded
only if an example is included in the answer.

(b)	females are carriers when they have dominant and recessive alleles
together;
recessive allele in carrier does not affect phenotype as dominant
allele also present;
gene is located on the X chromosome / gene is not located on Y
chromosome;
females are XX so can have dominant and recessive alleles/two
alleles of gene;
males are XY so only have dominant or recessive allele/one allele
of gene;
hemophilia/red-green colour blindness/other example of a sex-linked
characteristic;	4 max
 
(c)	(point) mutation of gene for hemoglobin;
CTC to CAC / GAG to GTG / substitution of T/thymine with A/adenine;
mRNA copy of gene is GUG instead of GAG;
valine instead of glutamic acid;
(in homozygotes) red blood cells become sickle-shaped;
(in homozygotes) less oxygen carried;
(in homozygotes) red blood cells do not survive long / burst / block
blood vessels/capillaries / circulatory problems may cause pain/
organ failure/example of symptom;
heterozygotes have malaria resistance;	5 max
(Plus up to [2] for quality)
[20]

15.	(a)	three copies/extra copy/trisomy of chromosome/pair 21	1
Do not accept chromatid.
 
(b)	occurs due to non-disjunction;
(homologous) chromosome/pairs/sister chromatids fail to separate;
some gametes have an extra chromosome;	2 max
 
(c)	male as sex chromosomes different size/both X and Y chromosomes present	1
To award [1], reason must be given.
 
(d)	gene for colour blindness is carried on X chromosome (sex linkage);
males have only one X chromosome so the allele is always expressed /
absent from Y chromosome;
the allele of the gene for colour blindness is recessive;
females must be homozygous to be colour-blind / heterozygous
females are carriers but not colour-blind;	2 max
[6]

16.	D
[1]

17.	C
[1]

18.	C
[1]

19.	A
[1]

20.	B
[1]

21.	C
[1]

22.	A
[1]

23.	(a)	Both must be correct for the mark to be awarded.
I. phosphate and II. hydrogen bond(s)	1
 
(b)	deoxyribose and phosphate added to base to show antiparallel orientation	1
Labels are not required but location of bonds and shape of deoxyribose
must be correctly shown.

(c)	transcription	1
 
(d)	polymerase chain reaction/PCR;
(DNA obtained from) blood/semen/hairs/other source of tissue;
combined with necessary raw materials/one example of raw material;
in thermal cycler / (PCR) machine;
DNA replicated many times;	2 max
[5]

24.	(a)	Down syndrome is caused by non-disjunction;
occurs during meiosis;
chromosome pairs fail to separate in meiosis I / chromatids in meiosis II /
anaphase II;
some gametes have an extra chromosome;
can lead to zygotes/individuals with an extra chromosome / individual
has 47 chromosomes;
in Down syndrome this would be trisomy 21/extra chromosome 21;
increased probability with increased age of mother/ages of parents;	5 max
 
(b)	skin colour is an example of polygenic inheritance;
many/more than two genes contribute to a person’s skin colour;
due to the amount of melanin in the skin;
combination of alleles determines the phenotype;
allows for range of skin colours / continuous variation of skin colour;
phenotypes do not follow simple Mendelian ratios of dominance and
recessiveness;
the environment also affects gene expression of skin colour /
sunlight/UV light stimulate melanin production;
the more recessive alleles there are, the lighter the skin colour; (vice versa)	5 max

(c)	caused by gene mutation;
(sickle-cell anemia) due to a base substitution (mutation);
changes the code on the DNA;
which leads to a change in transcription / change in mRNA;

which (in turn) leads to a change in translation / change in
polypeptide chain/protein;
(the tRNA) adds the wrong amino acid to the polypeptide chain;
glutamic acid replaced by valine;
produces abnormal hemoglobin;
causing abnormal red blood cell/erythrocyte shape / sickle shape;
which lowers the ability to transport oxygen;
sickle-cell allele is codominant;
homozygote/Hb^S Hb^S have sickle cell anemia/is lethal / heterozygote/
Hb^S Hb^A has the sickle trait/is carrier (and is more resistant to malaria);	8 max
(Plus up to [2] for quality)
[20]

25.	B
[1]

26.	C
[1]

27.	A
[1]

28.	C
[1]

29.	C
[1]

30.	A
[1]

31.	B
[1]

32.	D
[1]

33.	A
[1]

34.	D
[1]

35.	(a)	plasmid	1
 
(b)	DNA ligase involved; (DNA required to be consistent with syllabus)
seals gaps/nicks in DNA (strands);
makes sugar-phosphate bonds;	2 max
 
(c)	named example of DNA source and organism to which it is transferred;
benefit of the example of gene transfer;
possible harm from the example of gene transfer;
	Example:
gene transfer details [1 max]
e.g. Bt gene transferred from bacterium/Bacillus to maize
specific benefit [1 max]
e.g. corn borer/insect pest killed by Bt toxin increasing crop production;
e.g. less pesticides/fertilizers/chemicals needed so better for environment;
specific harmful effect [1 max]
e.g. non-target insects may be killed as well;
e.g. risk of cross-pollination may introduce gene to unintended species;
	Examiners may have to consult resources for legitimate alternative
examples.	3 max
[6]

36.	(a)	allele:	one specific form of a gene (occupying the same gene locus
as other alleles of the same gene)	1
 
(b)	I^BI^B and I^Bi	1
 
(c)	Award [1] for every two correct answers.
I.	bacterial cell/bacterium/prokaryote;
II.	plasmid;
III.	inserted/engineered/cloned/desired DNA/DNA from donor cell;
IV.	genetically modified/transformed/GM/recombinant organism/
cell/bacterium/host cell containing recombinant plasmid;	2 max
 
(d)	restriction enzymes / endonucleases;
ligases;
reverse transcriptase;
Award [1] for two correct responses.	1 max
[5]

37.	(a)	ecosystem is a community and its abiotic environment;
solar energy collected by autotrophs/plants (via photosynthesis);
moves through trophic levels via food;
only 5 to 20% transferred from one trophic level to next / never
100% efficient;
lost as metabolic heat/organic waste;
energy flow can be illustrated by pyramid shape;
organisms absorb nutrients from food/environment;
nutrients occur as complex organic matter in living organisms;
after death, saprotrophic bacteria and fungi (decomposers) breakdown
complex organic matter;
breakdown products are simpler substances;
absorbed into plants for resynthesis into complex organic matter/recycled;	6 max

(b)	offspring vary in traits;
variation results from sexual reproduction;
independent assortment of alleles (during meiosis of spermatogenesis/
oogenesis) contributes to variation;
meiosis is the cellular process that produces gametes;
crossing over (during meiosis) increases variation;
fertilization (combination of different genomes) contributes to variation;
more offspring may be produced than the environment can hold;
struggle for existence can occur;
offspring whose traits best adapt them to environment will survive/survival
of fittest;
change in environment will lead to survivors with new/different traits;
correct use of term natural selection/selective pressure;
variation is heritable / over time more offspring born with new trait;
change in gene pool;
when entire population (of a species) exhibits new trait, evolution
has occurred;	8 max
 
(c)
bryophyta | angiospermophyta
nonvascular/unspecialized tissue/no veins | vascular/specialized tissue/veins;
small/height up to 7 cm | tall/ height up to 100 m;
exist as organized masses of cells / “leafy” appearance | contain water-conducting cells (tissue)/food-conducting tissue/support tissue;
reproductive structures / capsules appear on stalks | have flowers;
microscopic spores | covered seeds/fruits;
sometimes hair-like extensions below growing surface/rhizoids | roots;
		4 max
	(Plus up to [2] for quality)
[20]

38.	D
[1]

39.	B
[1]

40.	A
[1]

41.	D
[1]

42.	C
[1]

43.	(a)	(i)	autosomes because the sex chromosomes/X and Y chromosomes
would be different lengths/sizes / would have different genes	1
 
(ii)	homologous because they have paired/formed a bivalent / tetrad /
there is crossing over between the chromosomes / they have the
same genes (in the same sequence) / they are the same size and shape	1
 
(b)	first prophase/first metaphase/prophase I/metaphase I	1
 
(c)

	Allow [1] only if the C allele is not on the short arm or the A and B alleles
are not on the long arm. Use a maximum of two ticks in your marking.	2
 
(d)	(gene) linkage / autosomal linkage	1
[6]

44.	(a)	Award [1] for each pair of statements in the table and [1] for any
statement below the table.
Unique sequences | Highly repetitive sequences
occur once in genome | occur many times;
long base sequences | short sequences/5–300 bases;
(may be) genes | not genes;
(may be) translated / coding sequences | never translated;
small differences between individuals | can vary greatly;
exons (are unique sequences) | introns (may be repetitive);
smaller proportion of genome | higher proportion of genome;
	satellite DNA is repetitive;
repetitive sequences are used for profiling;
prokaryotes do not (usually) contain repetitive sequences;	5 max
 
(b)	Award [1] for each of these structures clearly drawn and labelled.
four nucleotides shown in diagram with one nucleotide clearly labelled;
base, phosphate and deoxyribose (shown as pentagon) connected between
the correct carbons and labelled at least once;
backbone labelled as covalent bond between nucleotides correctly shown
as 3′ to 5′ bond;
two base pairs linked by hydrogen bonds drawn as dotted lines and labelled;
two H bonds between A and T and three H bonds between C and G;
adenine to thymine and cytosine to guanine; do not accept initials of bases
antiparallel orientation shown;	5

(c)	DNA sample obtained;
from hair/blood/semen/human tissue;
DNA amplified / quantities of DNA increased by PCR/polymerase
chain reaction;
satellite DNA/highly repetitive sequences are used/amplified;
DNA cut into fragments;
using restriction enzymes/restriction endonucleases;
gel electrophoresis is used to separate DNA fragments;
using electric field / fragments separated by size;
number of repeats varies between individuals / pattern of bands is unique to the individual/unlikely to be shared;
Award [5 max] for methods.
	forensic use / crime scene investigation;
example of forensic use e.g. DNA obtained from the crime scene/victim
compared to DNA of suspect / other example of forensic use;
paternity testing use e.g. DNA obtained from parents in paternity cases;
biological father if one half of all bands in the child are found in the father;
genetic screening;
presence of particular bands correlates with probability of certain
phenotype / allele;
other example;
brief description of other example;
Award [4 max] for aims.	8 max
	(Plus up to [2] for quality)
[20]

45.	(a)	Award [1] for each of the following clearly drawn and correctly labelled.
head and midpiece/mid-section/body;
tail/flagellum; (at least four times length of the head and containing fibres)
acrosome; (shown as distinct structure near front of head)
nucleus; (occupying more than half the width or length of head)
mitochondria; (as repetitive structures inside membrane of mid piece)
centriole; (between head and midpiece)
(plasma) membrane; (shown as single line covering whole cell)
microtubules; (in 9 plus 2 array)	5 max
 
(b)	crossing over/chiasmata formed during prophase I of meiosis;
pairing of homologous chromosomes/synapsis;
chromatids break (at same point); (do not accept chromatids overlap)
non-sister chromatids join up/swap/exchange alleles/parts;
X-shaped structure formed / chiasmata are X-shaped structures;
chiasma formed at position where crossing over occurred;
chiasmata become visible when homologous chromosomes unpair;
chiasma holds homologous chromosomes together (until anaphase);
Accept the above points in an appropriately annotated diagram.	5 max

(c)	non-disjunction;
chromosomes/chromatids do not separate / go to same pole;
non-separation of (homologous) chromosomes during anaphase I;
due to incorrect spindle attachment;
non-separation of chromatids during anaphase II;
due to centromeres not dividing;
occurs during gamete/sperm/egg formation;
less common in sperm than egg formation / function of parents’ age;
Down syndrome due to extra chromosome 21;
sperm/egg/gamete receives two chromosomes of same type;
zygote/offspring with three chromosomes of same type / trisomy /
total 47 chromosomes;
Accept the above points in an appropriately annotated diagram.	8 max
	(Plus up to [2] for quality)
[20]

46.	C
[1]

47.	A
[1]

48.	B
[1]

49.	B
[1]

50.	C
[1]

51.	(a)	(i)	(GMF) C	1
 
(ii)	 × 100;
=127% ; (units required) (allow answers in the range of 127 to 127.3)	2
 
(b)	error bars show the range/variability/uncertainty of the data / OWTTE;
error bars/standard deviation about the same length for day 0 and day 11 /
spread of data (around the means) about the same;
overlapping bars indicate that there is no (significant) difference in the
data/ means;
68% of population within one standard deviation;	2 max
 
(c)	inversely proportional / the higher the tolerance, the less the
growth / vice versa	1
 
(d)	first name/Oryza for genus / second name/sativa for species;
(all) members of Oryza sativa share special/unique features;
two names make a unique combination to designate species / worldwide
recognizable nomenclature;
varieties (japonica and indica) have some (consistent) differences
(in tolerance);	2 max
 
(e)	(i)	Sub1C	1
 
(ii)	Sub1A is expressed strongly/the most / Sub1A produces the
most RNA;
Sub1B (always) has the lowest expression/produces least
mRNA;
Sub1A expressed/produces mRNA for the longest
time/days 1 to 10;
Sub1C expressed/produces mRNA for the shortest
time/days 3 to 7;	2 max
 
(iii)	Sub1A only expressed/produces mRNA in indica / not/never
expressed/never produces mRNA in japonica;
Sub1C expressed/produces mRNA from day 1 in japonica,
but not indica;
Sub1B has lower expression/production of mRNA than
Sub1C in both varieties;
other accurate comparisons;	2 max
 
(f)	Sub1A;
is only expressed in indica;
indica is the variety showing submersion tolerance;	2 max

(g)	genetically modified rice/rice with Sub1A is more tolerant to
submersion;
can withstand seasonal flooding/torrential rain;
GMF/tolerant rice ensures greater harvest/provides more food
during flooding;	2 max
[17]

52.	(a)	anaphase	1
 
(b)	growth (through increasing cell number);
embryonic development;
tissue production/repair;
(asexual) reproduction;	2 max
 
(c)	uncontrolled mitosis/cell division	1
 
(d)	pair of homologous chromosomes moves in same direction/does not
separate during anaphase I / chromatids move in same direction/do
not separate during anaphase II;
leaving a cell with an (some) extra chromosome(s)/missing
chromosome(s);
an example; (e.g. Down syndrome / trisomy 21);	2 max
[6]

53.	A
[1]

54.	(a)	(i)	gid1-1	1
 
(ii)	between 10^–8 and 10 maltose ^–7 mol dm^–3 (units required)	1
 
(iii)	(breakdown) of starch to maltose	1

(b)	25% / 1 in 4 / 1:3 seeds produced would be homozygous recessive;
no response to/inhibits gibberellin in homozygous recessives results in less
germination;
less growth / dwarf plants produced; (must be in context)
would produce plants with infertile flowers that cannot produce rice grains;
would lower rice production/less yield because infertile plants cannot
produce seeds (that humans can eat);	3 max
 
(c)	(i)	Sub1C	1
 
(ii)	Sub1A is expressed strongly/the most / Sub1A produces the
most RNA;
Sub1B (always) has the lowest expression/produces least
mRNA;
Sub1A expressed/produces mRNA for the longest time/days
1 to 10;
Sub1C expressed/produces mRNA for the shortest time/days
3 to 7;	2 max
 
(d)	Sub1A;
is only expressed in indica / Sub1B and SubC are expressed in both
rice varieties;
indica is the variety showing submersion tolerance / vice versa for
japonica;	2 max
 
(e)	(i)	it increases the length of time before flowering	1
 
(ii)	long-day light exposure increases time before flowering only if
(OsGI) gene is not overexpressed/in WT and –/–;
long-day light exposure decreases time before flowering for +/–
and/or +/+;
length of day does not make much difference/makes least difference
for +/+;
overexpression for +/– reduces time before flowering;
–/– acts as a control / has nearly the same length of time before
flowering as WT;
Accept numerical answers if they are making a clear comparison.	2 max
 
(iii)	is a short-day plant because WT has shortest time/shorter
time before flowering in shorter days than longer days / as it takes
less time to flower under short day conditions;	1

(f)	codominant alleles show intermediate phenotype when both present;
could be codominant because homozygous +/+ shows longer time before
flowering than heterozygous;
–/– or homozygous not overexpressed has a slightly longer time before
flowering than WT so factors other than codominance could be
influencing flowering;
dominance shown with short-day light exposure while codominance
in long-day light exposure;
because presence causes overwhelming difference compared with
absence in short-day light exposure;
OsGI^+ could be dominant because its presence always causes longer
time before flowering;	2 max
 
(g)	the mutant gid1-1 would not be useful because it produces sterile plants;
genetically modified rice/rice with Sub1A is more tolerant to submersion/
can withstand seasonal flooding/torrential rain;
OsGI^+ varieties adapted to different latitudes / day length could be
produced (to overcome food shortages);	2 max
[19]

55.	B
[1]

56.	C
[1]

57.	D
[1]

58.	C
[1]

59.	A
[1]

60.	D
[1]

61.	C
[1]

62.	B
[1]

63.	C
[1]

64.	C
[1]

65.	D
[1]

66.	(a)	(i)	maize not modified/transformed with Bt (genes) / maize
that did not have Bt gene added / not genetically
modified / untreated maize	1
 
(ii)	50 – 12 = 38 (mm^2); Accept 12 – 50 = –38
(38 ÷ 50) × 100 = (–)76%; (ECF)	2
 
(b)	there was a decrease in damage by all three types of stem borers
compared to control;
there was almost no change in damage by Eldana compared to control;
there was almost no damage/little effect (to Bt maize type A) by
Sesamia (and Eldana);
Busseola caused the most damage (to Bt maize type A);	2 max

(c)	very efficient at controlling Sesamia;
type B is the most effective against the three stem borers collectively;
no type of Bt maize controlled Busseola well / vice versa , that is. Busseola
not well controlled by any types of Bt maize;
all types of Bt maize decreased Sesamia damage (significantly) / Bt
maize type E not damaged by Sesamia / vice versa;
Bt maize types C/H/I had more damage caused by Busseola (than
was caused in the control) / vice versa;
all types of Bt maize decreased Eldana damage (to some extent) / type
B was not damaged by Eldana / vice versa;
Eldana damage low in control / less effect;
cannot determine efficiency since data is about leaf damage and
stem borers may feed (preferentially) on other structures/stems/roots;	2 max
 
(d)	(268 – 215 =) 53 g
(Accept answers in range 51–57 g. Units required. No workings required.)	1
 
(e)	mass increases in all three groups;
increase is more rapid in beginning and tapers off later in the study;
mass seems to be levelling off in rats fed Bt and non-Bt maize / rate of
increase in mass is slowing down;
rats fed rat food always have higher mass/greater mass increase than
those fed either type of maize;	2 max
 
(f)	all three foods result in the same pattern of growth/mass gain / highest
rate of growth at start of study / tapering off later in the study;
Bt maize causes same amount of growth as non-Bt maize / appears to
be as good a food source as non-Bt maize / there is no significant
difference between Bt and non-Bt maize (in terms of mass gain);
corn (both types) appears to cause less growth/mass gain than rat
food / vice versa;
genetic modification does not affect growth/mass gain;
no evidence to support risk of Bt maize to growth/mass gain;
study does not investigate other possible risks of Bt maize to rats;
sample size is small / only 12 rats (in each group) so this may not
be enough to give trends;
only female rats tested, no males;	3 max
[13]

67.	(a)

	Award [1] for each labelled item shown above.
Award [2 max] if the two nucleotides are not shown in a single strand.	3 max
 
(b)	plasmid removed from bacteria;
plasmid cleaved/cut open by restriction enzymes;
desired gene/DNA extracted from donor;
DNA from donor cleaved using same restriction enzyme;
results in sticky ends;
with complementary base sequences;
pieces of DNA from two organisms mixed;
ligase used to splice pieces (DNA);
recombinant plasmids formed;
insertion into host cells;	6 max
 
(c)	translation is the synthesis of proteins/polypeptide chain/specific
sequence of amino acids;
translation occurs in cytoplasm/ribosomes;
uses information on the mRNA;
mRNA carries the genetic information of DNA;
mRNA binds to ribosome;
mRNA contains series of codons/base triplets;
tRNA binds with an amino acid and carries it to the ribosome;
tRNA has the anticodon that is complementary to the codon on the mRNA;
two tRNAs bind to a ribosome/mRNA at the same time;
(peptide) bond forms between two amino acids (carried by tRNA
molecules to the ribosome);
the first tRNA detaches, ribosome moves along mRNA and another
tRNA carrying an amino acid binds;
process repeats forming chain of amino acids/polypeptides;	9 max
	(Plus up to [2] for quality)
[20]

68.	(a)	transport against a concentration gradient / from low to high
concentration;
through protein pumps;
uses energy/ATP;	2 max

(b)	enzymes have a pH optimum;
active site works best at this pH;
activity decreases above and below the optimum;
by interfering with H-bonding/active site structure;
denaturing by extremes of pH so enzyme activity/reaction stops;	3 max
 
(c)	yeast: pyruvate to ethanol and carbon dioxide;
humans: pyruvate to lactic acid;
Award [1 max] if products are appropriately linked to organisms
without the mention of pyruvate.	2
[7]

69.	D
[1]

70.	A
[1]

71.	A
[1]

72.	B
[1]

73.	C
[1]

74.	B
[1]

75.	C
[1]

76.	C
[1]

77.	C
[1]

78.	A
[1]

79.	C
[1]

80.	B
[1]

81.	(a)	50 – 12 = 38 (mm^2); Accept 12–50 = –38
(38 ÷ 50) x 100 = (–)76%; (ECF)	2
 
(b)	Sesamia (was most successfully controlled);
in control plants Sesamia caused most damage;
all types of Bt/genetically modified maize/A–I show (significant) decrease
in damage by Sesamia;
mark for correct numerical comparison;
Sesamia caused no damage to type E/ in one instance;
Busseola not controlled/affected by Bt/genetically modified maize/
caused largest amount of damage in types A–I/increased damage in
some varieties;
Eldana controlled by some types of maize / B/C/D but not others /
Eldana caused least damage in control and not much difference in
many maize types;	3 max
 
(c)	males: (440 – 325 =) 115 g; (Accept answers in range 105–125 g)
females: (268 – 215 =) 53 g; (Accept answers in range 51–57 g)
Units required, no workings required.	2

(d)	(promotes) highest rate of growth at start of study / tapering off later in
the study;
Bt maize appears to cause less growth/mass gain than rat
food / vice versa;
more pronounced difference in females;
no difference in growth/mass gain between Bt and non-Bt maize;	2 max
 
(e)	(Bt) maize may not be as good as the (commercially prepared) rat food;
Bt maize appears to be as good a food source as non-Bt maize;
Bt maize an acceptable/safe food source;
Answers require a judgement about Bt maize as a food source rather
than a description.	1 max
 
(f)	decomposers / recycle nutrients / cause decay / nitrification/nitrogen
fixation / denitrification	1
 
(g)	(for both groups) overall biomasses were higher during flowering than
harvest / vice versa
the microbial biomass for the Bt crop was (slightly) lower than for the
non-Bt crops at flower time;
the microbial biomass for the Bt crop was (slightly) higher than for
the non-Bt crops at harvest time;	2 max
 
(h)	data does not support the hypothesis as there is little difference between
biomass found in the soil (surrounding) roots (of the Bt and non-Bt) at
either time;
data does not support the hypothesis as there is a slightly positive effect
at harvest;
data supports hypothesis as there is a slightly negative effect at flowering;	2 max
 
(i)	(i)	α helix / alpha helix	1
 
(ii)	hydrogen bonds;
between the turns of the helix (rather than between R-groups);
bonds between carboxyl and NH groups/C-O---H-N;	2 max
 
(iii)	non-polar amino acids/R-groups;
(inner part of phospholipid) bilayer is hydrophobic/non-polar;	2
[20]

82.	(a)	(i)		1
 
(ii)	unenclosed seeds, starchy and tunica present, sugary /
 and  (both needed)	1
 
(iii)	crossing over;
between non-sister chromatids (in prophase I);
results in exchange of alleles / change in linkage groups;
so some gametes are T     e or t     E; (linkage notation not expected)
test cross expect ratio of two phenotypes / correct Punnett Square
showing test cross;
but instead get four phenotypes with smaller percentage of
recombinants;
Above points can be shown in diagrams.	2 max
 
(b)
angiospermophytes | bryophytes
flowering | non-flowering;
(true) roots | rhizoids/no true roots;
(true) leaves | scales / thallus/no true leaves;
seeds produced | spores produced (in capsule);
waxy cuticle | no cuticle;
vascular (tissue) | non-vascular/no vascular tissue
		2 max
[6]

83.	(a)	non-disjunction (can cause Down syndrome);
occurs when pair of homologous chromosomes fails to separate
during meiosis;
one gamete/daughter cell receives two chromosomes / diagram
showing this;
occurs in anaphase I/II of meiosis;
fertilization involving this gamete leads to change in chromosome
number/47 chromosomes;
most common form of Down is trisomy 21/extra chromosome 21;
increase risk of Down syndrome with increased age of mother;	4 max

(b)	oogenesis is process by which female gametes/eggs are produced;
begins during fetal development;
oogonia/large number of cells formed by mitosis;
oogonia/cells enlarge/undergo cell growth/become primary oocytes;
begin first meiotic division but stop in Prophase I;
until puberty;
(at puberty) some follicles develop each month in response to FSH;
(primary oocyte) completes first meiotic division;
forms two cells of different/unequal sizes / unequal distribution
of cytoplasm;
(creating a) polar body;
polar body eventually degenerates;
larger cell/secondary oocyte proceeds to meiosis II;
stops at prophase II;
meiosis II completed if cell is fertilized;
ovum and second polar body formed;	8 max
 
(c)	To award full marks, discussion must contain both pro and con
considerations.
	pros/positive considerations: [3 max]
chance for infertile couples to have children;
decision to have children is clearly a conscious one due to difficulty of
becoming pregnant;
genetic screening of embryos could decrease suffering from genetic diseases;
spare embryos can safely be stored for future pregnancies/used for
stem cell research;
	cons/negative considerations: [3 max]
IVF is expensive and might not be equally accessible;
success rate is low therefore it is stressful for the couple;
it is not natural/cultural/religious objections;
could lead to eugenics/gender choice;
could lead to (unwanted) multiple pregnancies with associated risks;
production and storage of unused embryos / associated legal issues /
extra embryos may be used for (stem cell) research;
inherited forms of infertility might be passed on to children;
Accept any other reasonable answers.	6 max
	(Plus up to [2] for quality)
[20]

84.	(a)	character affected/influenced/defined/determined/controlled by
two or more genes	1

(b)	human skin colour can vary from pale to very dark / amount of
melanin varies;
skin colour/melanin controlled by (alleles from) at least three/several
genes;
no alleles are dominant / alleles are co-dominant / incomplete dominance;
many different possible combinations of alleles;
skin colour controlled by cumulative effect/combination of genes/alleles;
Award the above marking points for any other valid example.	2 max
 
(c)	sex linked condition;
carried on an X chromosome / absent from Y chromosome;
if present in male causes colour blindness;
(allele is) recessive so heterozygous females are not colour blind;
homozygous females are colour blind;
Do not allow carried on sex chromosome.	3 max
[6]

85.	A
[1]

86.	C
[1]

87.	B
[1]

88.	C
[1]

89.	C
[1]

90.	(a)	cells undergoing mitosis are used for karyotyping;
process of mitosis is stopped at (mitotic) metaphase;
chromosomes (cut from photographs) are arranged in pairs of similar
structure/homologous chromosomes;
allows abnormalities in the chromosome number/appearance to be seen;
any valid example (e.g. in Down syndrome / gender of fetus);
detected by identifying unique feature (e.g. trisomy 21 / one extra
chromosome / 47 chromosomes);
Award [3 max] for an example with no description of karyotyping.	4 max
 
(b)	restriction enzymes/endonucleases cut a small fragment of DNA from
an organism;
same restriction enzymes used to cut DNA of plasmid / e.g. E. coli;
sticky ends are the same in both cases;
fragment of DNA is inserted into the plasmid;
spliced together by ligase;
to make recombinant DNA/plasmids;
recombinants can be inserted into host cell and cloned;	5 max
 
(c)	genetic modification is when the DNA/genotype of an organism is
artificially changed;
genetic modification alters some characteristic/phenotype of the organism;
named example with modification (e.g. salt tolerance in tomato plants);
	benefits: [5 max]
allows crops to be grown where they would not grow naturally;
provides more food;
economic benefits;
expands world’s productive farmland;
reduces the need to clear rainforests to grow crops;
lowers cost of production;
less pesticides/fertilizers/chemicals needed so better for environment;
Award marks for any valid benefit consistent with a named example.
	harmful effects: [5 max]
may be released into natural environment;
may affect food chains / unintended effects on other organisms;
may affect consumers e.g. allergies/health risks;
unfair to smaller farmers who cannot compete;
long-term effects are unknown;
risk of cross-pollination;
risk of long-term contamination of soil;
Award marks for any harmful effect consistent with the named example.	9 max
	(Plus up to [2] for quality)
[20]

91.	D
[1]

92.	D
[1]

93.	B
[1]

94.	A
[1]

95.	(a)	genes that are located on the same chromosome (form a linkage group)	1
 
(b)	;
;
Award [1 max] if the candidate does not use the same format, but
gives the correct letters Ggff and ggFf.	2
 
(c)	(recombination) occurs in prophase 1 of meiosis;
homologous chromosomes come together in pairs;
chiasmata form between the (non-sister) chromatids;
chromosomes exchange segments / crossing over takes place;	3 max
 
(d)	tRNA attaches to (specific) amino acid;
tRNA (with amino acid) moves to the ribosome;
anticodon of tRNA binds with codon of mRNA;	2 max
[8]

96.	D
[1]

97.	C
[1]

98.	D
[1]

99.	C
[1]

100.	A
[1]

101.	(a)	polymerase chain reaction and electrophoresis	1
Both required for [1]
 
(b)	all bands on the DNA profile of E / evidence match those of S2 / no agreement
between DNA fragments and S1;
suspect 2 / S2 was present at the crime scene;	2
[3]

102.	(a)	Award [1] for two of the following
pre-natal development of male genitalia;
development of male secondary sexual characteristics / name of
specific characteristic;
maintenance of sex drive;	1 max
 
(b)	red-green colour-blindness is a sex-linked character / gene located on
X-chromosome;
boy inherits X chromosome from mother, only inherits Y chromosome
from father;
boy’s mother must have been carrying the gene;
he inherited it from mother’s father / maternal grandfather;	3 max
[4]

103.	(a)	Award [1] for each of the following clearly drawn and correctly labelled.
Simple shapes may be used but must have a key or be clearly labelled.
	two nucleotide strands (note that strands must be drawn antiparallel
although it does not need to be labelled as such);
alternating sugar-phosphate backbone;
complementary base pairs shown, A-T and C-G;
hydrogen bonds between base pairs;
covalent bonds between sugar and phosphate groups / between sugar and bases;
	nucleotide including sugar, phosphate and base (with parts correctly
connected);	4 max
 
(b)	mutation is a change in the genetic make-up;
base substitution mutation occurs when one (nitrogenous) base in DNA chain is
replaced by another;
this is a gene mutation / change in the base sequence of a gene;
effect of mutation ranges from no effect / no change in amino acid sequence to
drastic changes;
sickle-cell anaemia involves change in gene for one of polypeptides in
hemoglobin / Hb / HB^A;
GAG has mutated to GTG (on DNA);
adenine replaced by thymine in DNA;
transcription of DNA produces the triplet GUG instead of GAG on mRNA;
one codon is different in mRNA;
new codon is for valine rather than glutamic acid;
tRNA brings amino acid to ribosome during translation;
different amino acid placed in polypeptide chain being formed by translation;
the two amino acids differ in solubility / have different properties / valine causes
HB^S to be less soluble;
causes red blood cells to become sickle shaped / carry oxygen less efficiently;
HB^S allele causes sickle-cell anaemia but gives resistance to malaria;	8 max
 
(c)	comparative anatomy of groups of animals or plants shows certain
structural features are basically similar;
homologous structures are those that are similar in shape in different types
of organisms;
structural similarities imply a common ancestry;
(homologous structures) used in different ways;
	example is pentadactyl limb in vertebrates / modification of ovary wall or
pericarp to aid seed dispersal / other suitable example;
	adapted to different mode of locomotion in particular environment / 
example of two differences such as bat’s wing and human hand;
illustrates adaptive radiation since basic plan adapted to different niches;
the more exclusive the shared homologies the closer two organisms are related;
certain homologous structures in some species with no apparent function such as
human appendix (homologous with functional appendix in herbivores);	6 max
(Plus up to [2] for quality)
[20]

104.	(a)	reverse transcriptase obtained from viruses;
used to convert mRNA to cDNA;
mature mRNA will not contain introns;
bacteria cannot undertake post-transcriptional modification;
cDNA can be inserted into bacterial host;
example of use;	3 max
 
(b)	production of beer;
wine;
bread;		2 max
[5]

105.	(a)	DNA and protein	1
 
(b)	crossing over / chiasmata;
shuffles alleles;
random orientation of chromosomes;
at metaphase I:
at metaphase II;	2 max
 
(c)	all four genotypes shown: TTRr, TTrr, TtRr, Ttrr;
phenotype individually identified / 2 tall round and 2 tall wrinkled;	2
Cannot use genotype letters by themselves to mean phenotypes eg cannot state that the phenotype of a tall round plant is TR etc
 
(d)	non-disjunction	1
[6]

IB Questionbank Biology