1 [75 marks]
1.
[Maximum mark: 1]
22N.1.SL.TZ0.16
[1]
Markscheme
D
2.
[Maximum mark: 1]
22N.1.SL.TZ0.24
[1]
Markscheme
D
3.
[Maximum mark: 1]
22M.1.SL.TZ1.14
[1]
Markscheme
A
4.
[Maximum mark: 1]
22M.1.SL.TZ2.14
[1]
Markscheme
C
NOTE FOR TEACHERS: The credit line under the image may give students an indication of the
correct answer. Teachers may wish to adjust their quizzes/exams accordingly.
5.
[Maximum mark: 1]
21N.1.SL.TZ0.16
[1]
Markscheme
C
6.
[Maximum mark: 1]
21M.1.SL.TZ1.17
[1]
Markscheme
D
7.
[Maximum mark: 1]
22M.1.SL.TZ2.16
[1]
Markscheme
B
8.
[Maximum mark: 1]
21M.1.HL.TZ1.35
[1]
Markscheme
B
9.
[Maximum mark: 1]
20N.1.HL.TZ0.12
[1]
Markscheme
D
10.
[Maximum mark: 1]
21M.1.HL.TZ1.35
[1]
Markscheme
B
11.
[Maximum mark: 1]
20N.1.HL.TZ0.12
[1]
Markscheme
D
12.
[Maximum mark: 1]
17N.1.HL.TZ0.10
[1]
Markscheme
D
13.
[Maximum mark: 1]
17M.1.SL.TZ1.14
[1]
Markscheme
C
14.
[Maximum mark: 1]
17M.1.SL.TZ1.16
[1]
Markscheme
A
15.
[Maximum mark: 1]
17M.1.SL.TZ2.14
[1]
Markscheme
A
16.
[Maximum mark: 1]
17M.1.HL.TZ1.35
[1]
Markscheme
D
17.
[Maximum mark: 1]
17M.1.HL.TZ2.21
[1]
Markscheme
D
18.
[Maximum mark: 4]
17M.3.SL.TZ1.17
(a.i)
[1]
Markscheme
infants from mothers with low levels of vitamin D have an increased chance of developing
seizures
Accept answers in the converse.
(a.ii)
[1]
Markscheme
lack of vitamin D in breast milk OR lack of vitamin D leads to lack of bone
mineralization/calcium uptake
(b)
[1]
Markscheme
it can be synthesized by humans «in skin»
(c)
[1]
Markscheme
a. they cannot be synthesized by humans
b. they must be present in the diet
19.
[Maximum mark: 3]
17M.3.HL.TZ2.18
[3]
Markscheme
a. determine the initial and final/change in mass of the food sample
b. determine initial and final/change in temperature of water
c. ignite sample and place burning sample under a known volume/mass of water
d. energy content is determined using formula
e. divide energy of water by mass of the food sample OWTTE
20.
[Maximum mark: 7]
18M.2.HL.TZ2.3
(a.i)
[2]
Markscheme
a. anaphase II
b. as four daughter cells are being formed
OR
the centromeres split / sister chromatids separate
OR
sister chromatids/ chromosomes are pulled «by the spindle microtubules» to opposite poles
(a.ii)
[2]
Markscheme
a. two «or more» traits/genes are inherited independently of one another. Accept vice versa.
b. observed for traits/genes that are not linked/far apart on the chromosome
Can be shown in annotated diagram.
c. «due to homologous» chromosomes aligning independently/randomly on equator during
metaphase I/meiosis I
d. during anaphase I homologues pulled to separate poles
Can be shown in annotated diagram.
(b)
[3]
Markscheme
a. correct parental genotypes shown / Ff ii, FfIA IB
b. Punnett square with correct gametes shown
c. correct probability:
1
8
OR
12.5%
Must use blood type symbols IB IA and i. No specific letters required to represent cystic fibrosis
allele though dominant and recessive must be apparent.
21.
[Maximum mark: 10]
19M.2.HL.TZ1.2
(a)
[2]
Markscheme
a. prokaryotes have circular DNA/chromosome but eukaryote chromosomes linear/OWTTE ✔
OR
eukaryotes have telomeres/centromeres whereas prokaryotes do not ✔
b. some prokaryotes have plasmids whereas eukaryotes do not ✔
c. eukaryotes have multiple chromosomes whereas prokaryotes «typically» have only one ✔
d. histones/nucleosomes/proteins associated with DNA in eukaryotes but not in
prokaryotes/naked DNA in prokaryotes
OR
eukaryote DNA can coil/supercoil/condense «due to histones» but not prokaryote DNA ✔
(b)
[2]
Markscheme
a. genetic disease/caused by a gene
OR
inherited «from parents»
OR
caused by mutation «of a gene» ✔
b. base substitution
OR
GAG → GTG ✔
c. hemoglobin gene mutated / different allele/form/version of hemoglobin gene
OR
HbA → HbS ✔
d. leads to change in amino acid sequence «in hemoglobin»
OR
glutamic acid → valine ✔
e. only homozygotes have full disease/sickled cells / heterozygote has milder form
OR
hemoglobin crystallizes at low oxygen concentration ✔
f. «selected for/spreads in population» as it gives resistance to malaria ✔
(c.i)
[1]
Markscheme
male because «X and» Y chromosome present
OR
male because sex chromosomes/last two chromosomes/pair 21 are unpaired/different «from
each other»/not homologous ✔
The answer must include “male” and the reason.
(c.ii)
[1]
Markscheme
21
(d.i)
[2]
Markscheme
(d.ii)
[2]
Markscheme
a. not a 1:1:1:1 ratio «because of linkage»
OR
not independent assortment
OR
grey normal and black vestigial types/parental combinations/double dominant and double
recessive were commoner than 25 %/commoner than expected ✔
b. «linked genes» so were on the same chromosome ✔
c. grey body vestigial wing and black body normal wing are recombinants
OR
2 % plus 3 % of the offspring are recombinants ✔
d. recombinants due to crossing over/exchange of genes between «non-sister» chromatids
OR
2 % and 3 % of offspring were due to crossing over
OR
genes inherited together unless separated by crossing over ✔
e. crossing over between the two loci/between the two genes on the chromosomes ✔
f. few recombinants/not much crossing over because genes/gene loci close together ✔
Accept any of these points from an annotated diagram.
22.
[Maximum mark: 15]
22M.2.SL.TZ1.7
(a)
[3]
Markscheme
a. ribose drawn as a pentagon and labelled;
b. base linked correctly (to C1) of ribose and labelled;
c. phosphate linked correctly (to C5) of ribose and labelled;
Award [2 max] if more than one nucleotide drawn.
“Sugar” alone is insufficient.
(b)
[5]
Markscheme
(c)
[7]
Markscheme
a. antibiotics can (generally) kill/destroy bacteria;
b. some bacteria show variation/antibiotic resistance;
c. variation/resistance is due to a random mutation;
d. resistant bacteria are not killed/destroyed by the antibiotic
OR
bacteria without the mutation die;
e. (resistant) bacteria have a selective advantage / unequal success;
f. the bacteria with this variation/resistance reproduces/multiplies;
g. mutation/gene is passed on to the offspring / the offspring will be resistant to the
antibiotic;
h. resistant bacteria become more common;
i.
bacteria have evolved to be resistant to the antibiotic;
Award [6 max] if pathogen is used instead of bacteria throughout the answer with no mention of
bacteria.
23.
[Maximum mark: 4]
18M.3.SL.TZ1.19
[4]
Markscheme
Causes:
a. deficiency in an essential nutrient
b. excess of a nutrient
c. may be due to social/socioeconomic/political factors
d. unbalanced diet can result from malfunction of the hypothalamus
Consequences:
e. starvation can lead to breakdown of body tissues
f. obesity can lead to other health problems/diabetes/CHD
g. anorexia can lead to organ failure/serious health problems
h. consequence of a named excess/deficiency
Maximum 3 marks if both causes and consequences not mentioned.
24.
[Maximum mark: 15]
17M.2.HL.TZ2.8
(a)
[4]
Markscheme
a. mitosis is the division of a nucleus to produce two genetically identical daughter nuclei
b. consists of four phases: prophase, metaphase, anaphase, telophase
c. cytokinesis occurs after mitosis
d. interphase is the metabolically active phase between cell divisions OWTTE
e. the interphase consists of the S phase, G1 and G2
f. DNA replicates in the S phase
g. cell growth
OR
preparation for mitosis
OR
duplication of organelles in G1 and G2
(b)
[3]
Markscheme
a. «crossing over/chiasmata shown between» homologous chromosomes
b. centromere drawn and labelled
c. single strand break «SSB»/DNA cut between homologous chromosomes
d. non-sister chromatids labelled
OR
sister chromatids labelled
e. chiasma between homologous chromosomes labelled «shown forming after SSB»
Homologous chromosomes must be labelled and correctly drawn.
It is likely that more than one diagram will need to be included to demonstrate the stages.
(c)
[8]
Markscheme
a. mRNA conveys genetic information from DNA to the ribosomes «where it guides
polypeptide production»
b. gene expression requires the production of specific mRNA «through transcription»
c. most genes are turned off/not being transcribed at any one time/regulated
OR
some genes are only expressed at certain times
d. some genes are only expressed in certain cells/tissues
OR
«cell» differentiation involves changes in gene expression
e. transcription factors/proteins can increase/decrease transcription
f. hormones/chemical environment of cell can affect gene expression
g. example of cell environment
eg: auxin/insulin/cytoplasmic gradient in embryo
h. transcription factors/proteins may prevent or enhance the binding of RNA polymerase
i. nucleosomes limit access of transcription factors to DNA/regulate gene
expression/transcription
OR
activate or silence genes
j. DNA methylation/acetylation appears to control gene expression «as epigenetic factor»
OR
methylated genes are silenced
k. «some» DNA methylation patterns are inherited
l. introns may contain positive or negative gene regulators
OR
gene expression can be regulated by post-transcriptional modification/splicing/mRNA
processing
© International Baccalaureate Organization, 2023