MCV4U UNIT 4 – EXTENSIONS
ASSESSMENT OF LEARNING PRACTICE
EXAMINATION 2026 QUESTIONS
WITH ANSWERS GRADED A+
◍ Alleles that are neither dominant nor recessive to one another, so both
alleles are always expressed in the phenotype..
Answer: Codominant
◍ The inheritance of a single gene.
Answer: Monohybrid inheritance
◍ In an investigation into taxis, termites were split into 3 groupsGroup A had
their eyes covered (moved straight up)Group B had their antenna covered
(moved straight to light)Group C were the control (moved diagonally up and
towards light)What does Group A show about the factors controlling termite
movement?.
Answer: Antenna involved in response to gravityDon't respond to light as
eyes are covered
◍ In a graph of membrane permeability against time, the line for Na+ ions
increases rapidly between 0.5 and 0.7msExplain why.
Answer: Na+ gated channel proteins openNa+ move into axon by facilitated
diffusionNeurone depolarisedStimulates more Na+ channels to open
◍ Give 2 properties of stem cells.
Answer: UndifferentiatedCan keep dividing / replicating
◍ Physical, behavioural, biochemical expression of an organisms genotype.
Answer: Phenotype
◍ How might the insertion of DNA into a cell cause cancer?.
, Answer: DNA disrupts tumor suppressor geneTumor suppressor gene not
transcribed/inactivatedRate of cell division increases (not controlled)
◍ Succinate dehydrogenase catalyses a reaction in the Krebs Cycle In
micrograph A there was a high amount of the enzymeIn micrograph B there
was a lower amount of the enzymeWhich micrograph is of a slow muscle
fibre and why?.
Answer: AMore succinate dehydrogenaseSo more aerobic respiration /
mitochondria
◍ Explain the distribution of mitochondria in slow muscle fibres.
Answer: Distributed near the surfaceShort diffusion path for O2O2 for ETC
of aerobic respiration in mitochondria
◍ You could use an optical microscope and a slide of stained muscle fibres to
calculate the diameter of a muscle fibreExplain how.
Answer: Use a graticuleCalibrate against something of known size e.g ruler
◍ A student found the mean diameter of muscle fibresExplain two precautions
that should have been taken when sampling these.
Answer: Large sample size - representativeRandom sample - eliminate bias
◍ The type of genes an individual has.
Answer: Genotype
◍ A graph shows blood glucose concentration against urine concentration
measured using urine test(colour = range of 1-4) Evaluate the use of this
urine test to measure blood glucose concentration.
Answer: Positive correlationBut range of results for particular
values/overlapSubjective and arbitrary
◍ Explain how a DNA probe could be used to show if alleles of genes were
the same.
Answer: DNA probe has specific base sequenceComplementary to the
specific base sequence of the alleleBind to both allelesLabel would show up
in both
,◍ Alles that is always expressed in the phenotype.
Answer: Dominant
◍ Prey index is based on how much food is available to a predatorExplain why
this is better than biomass.
Answer: Wolves don't eat all prey Inedible bits make up DIFFERENT
PROPORTIONS
◍ Only expressed in the phenotype when homozygous.
Answer: Recessive
◍ both alleles are the same.
Answer: Homozygous
◍ In a graph of wolf numbers against number of animals in a given area, the
line of best fit increasesThere are some outliersExplain what these shows
about the factors affecting wolf numbers.
Answer: Limited by preyWhen number of prey increase, number of wolves
increasesLarge range so other factors involved
◍ Explain how acetylcholine contributes to a synapse being unidirectional.
Answer: Acetylcholine receptors only on post synaptic
membraneAcetylcholine released from pre-synaptic membraneDiffuses
across synpatic cleft from high to low concentrationOnly binds to
acetylcholine receptors
◍ Explain why the percentage of each base may differ in different parts of the
chromosomes.
Answer: Different genesDifferent base sequences
◍ Both alleles for a specific gene are different.
Answer: Heterozygous
◍ Position of a gene on a chromosome.
Answer: Loci
◍ A set of instructions for a specific polypeptide.
Answer: Gene
, ◍ Different forms of a gene.
Answer: Allele
◍ 1. Expected ratios are probability 2. Sexual reproduction is random due to
random fusion of gametes and random assortment homologous
chromosomes.3. Small sample size 4. Linked genes.
Answer: Suggest four reasons why observed ratios are not the same as
expected ratios (4).
◍ In restriction mapping what would be true if some of the DNA was not
digested fully.
Answer: Large pieces of DNA presentAdd up to more than total length of
original DNAUndigested added to original length
◍ 1. Homologous chromosomes pair up 2. Crossing over / chiasmata form;3.
Produces new combination of alleles4. Chromosomes separate at random5.
This produces varying combinations of genes6. Chromatids separated at
meiosis II.
Answer: Meiosis results in cells that have the haploid number of
chromosomes and show genetic variation. Explain how. (6)
◍ Why might siRNA be useful in treating some diseases?.
Answer: Some diseases are geneticsiRNA inhibits translation and
production of harmful protein
◍ 1. Refer to the specific individuals (using their number)2. Explain what
happened with the genes (passed on recessive/dominant)3. Describe the
genotype of your examples and mention their phenotype
(homozygous/heterozygous etc).
Answer: Pedigree Questions Mark Scheme (3)
◍ Group of organisms of the same species occupying a particular space at a
particular time that can potentially interbreed to produce fertile offspring..
Answer: Populations
◍ In the first 40% of the time spent as a pupa, the RNA concentration
ASSESSMENT OF LEARNING PRACTICE
EXAMINATION 2026 QUESTIONS
WITH ANSWERS GRADED A+
◍ Alleles that are neither dominant nor recessive to one another, so both
alleles are always expressed in the phenotype..
Answer: Codominant
◍ The inheritance of a single gene.
Answer: Monohybrid inheritance
◍ In an investigation into taxis, termites were split into 3 groupsGroup A had
their eyes covered (moved straight up)Group B had their antenna covered
(moved straight to light)Group C were the control (moved diagonally up and
towards light)What does Group A show about the factors controlling termite
movement?.
Answer: Antenna involved in response to gravityDon't respond to light as
eyes are covered
◍ In a graph of membrane permeability against time, the line for Na+ ions
increases rapidly between 0.5 and 0.7msExplain why.
Answer: Na+ gated channel proteins openNa+ move into axon by facilitated
diffusionNeurone depolarisedStimulates more Na+ channels to open
◍ Give 2 properties of stem cells.
Answer: UndifferentiatedCan keep dividing / replicating
◍ Physical, behavioural, biochemical expression of an organisms genotype.
Answer: Phenotype
◍ How might the insertion of DNA into a cell cause cancer?.
, Answer: DNA disrupts tumor suppressor geneTumor suppressor gene not
transcribed/inactivatedRate of cell division increases (not controlled)
◍ Succinate dehydrogenase catalyses a reaction in the Krebs Cycle In
micrograph A there was a high amount of the enzymeIn micrograph B there
was a lower amount of the enzymeWhich micrograph is of a slow muscle
fibre and why?.
Answer: AMore succinate dehydrogenaseSo more aerobic respiration /
mitochondria
◍ Explain the distribution of mitochondria in slow muscle fibres.
Answer: Distributed near the surfaceShort diffusion path for O2O2 for ETC
of aerobic respiration in mitochondria
◍ You could use an optical microscope and a slide of stained muscle fibres to
calculate the diameter of a muscle fibreExplain how.
Answer: Use a graticuleCalibrate against something of known size e.g ruler
◍ A student found the mean diameter of muscle fibresExplain two precautions
that should have been taken when sampling these.
Answer: Large sample size - representativeRandom sample - eliminate bias
◍ The type of genes an individual has.
Answer: Genotype
◍ A graph shows blood glucose concentration against urine concentration
measured using urine test(colour = range of 1-4) Evaluate the use of this
urine test to measure blood glucose concentration.
Answer: Positive correlationBut range of results for particular
values/overlapSubjective and arbitrary
◍ Explain how a DNA probe could be used to show if alleles of genes were
the same.
Answer: DNA probe has specific base sequenceComplementary to the
specific base sequence of the alleleBind to both allelesLabel would show up
in both
,◍ Alles that is always expressed in the phenotype.
Answer: Dominant
◍ Prey index is based on how much food is available to a predatorExplain why
this is better than biomass.
Answer: Wolves don't eat all prey Inedible bits make up DIFFERENT
PROPORTIONS
◍ Only expressed in the phenotype when homozygous.
Answer: Recessive
◍ both alleles are the same.
Answer: Homozygous
◍ In a graph of wolf numbers against number of animals in a given area, the
line of best fit increasesThere are some outliersExplain what these shows
about the factors affecting wolf numbers.
Answer: Limited by preyWhen number of prey increase, number of wolves
increasesLarge range so other factors involved
◍ Explain how acetylcholine contributes to a synapse being unidirectional.
Answer: Acetylcholine receptors only on post synaptic
membraneAcetylcholine released from pre-synaptic membraneDiffuses
across synpatic cleft from high to low concentrationOnly binds to
acetylcholine receptors
◍ Explain why the percentage of each base may differ in different parts of the
chromosomes.
Answer: Different genesDifferent base sequences
◍ Both alleles for a specific gene are different.
Answer: Heterozygous
◍ Position of a gene on a chromosome.
Answer: Loci
◍ A set of instructions for a specific polypeptide.
Answer: Gene
, ◍ Different forms of a gene.
Answer: Allele
◍ 1. Expected ratios are probability 2. Sexual reproduction is random due to
random fusion of gametes and random assortment homologous
chromosomes.3. Small sample size 4. Linked genes.
Answer: Suggest four reasons why observed ratios are not the same as
expected ratios (4).
◍ In restriction mapping what would be true if some of the DNA was not
digested fully.
Answer: Large pieces of DNA presentAdd up to more than total length of
original DNAUndigested added to original length
◍ 1. Homologous chromosomes pair up 2. Crossing over / chiasmata form;3.
Produces new combination of alleles4. Chromosomes separate at random5.
This produces varying combinations of genes6. Chromatids separated at
meiosis II.
Answer: Meiosis results in cells that have the haploid number of
chromosomes and show genetic variation. Explain how. (6)
◍ Why might siRNA be useful in treating some diseases?.
Answer: Some diseases are geneticsiRNA inhibits translation and
production of harmful protein
◍ 1. Refer to the specific individuals (using their number)2. Explain what
happened with the genes (passed on recessive/dominant)3. Describe the
genotype of your examples and mention their phenotype
(homozygous/heterozygous etc).
Answer: Pedigree Questions Mark Scheme (3)
◍ Group of organisms of the same species occupying a particular space at a
particular time that can potentially interbreed to produce fertile offspring..
Answer: Populations
◍ In the first 40% of the time spent as a pupa, the RNA concentration
