OCR A LEVEL BIOLOGY PAPER 2
EXAMINATION TEST 2026 QUESTIONS AND
CORRECT SOLUTIONS
◉ Heterozygous. Answer: When an organism has two different
alleles of the same gene.
◉ Genotype. Answer: Description of an organism's alleles.
◉ Phenotype. Answer: Characteristics of an organism as a result of
the expression of its genotype and the environment.
◉ Gene. Answer: Section of a chromosome that codes for a
polypeptide.
◉ Allele. Answer: Alternative version of the same gene.
◉ Gene locus. Answer: Location of a gene on a chromosome.
◉ Dominant allele. Answer: Allele that is always expressed in the
phenotype.
,◉ Recessive allele. Answer: Allele that is only expressed in the
phenotype when there are two of them i.e. in a homozygote.
◉ Codominant allele. Answer: Both alleles are expressed in the
phenotype.
◉ Multiple alleles. Answer: More than 2 alleles for a particular gene.
◉ Sex linkage. Answer: Characteristic or trait controlled by a gene
found on the sex chromosomes.
◉ Homologous chromosomes. Answer: Pair of chromosomes that
carry genes for the same characteristics, at the same gene loci.
◉ Autosome. Answer: Any chromosome that is NOT a sex
chromosome.
◉ Autosomal linkage. Answer: Genes coding for different
characteristics, found on the same non-sex chromosome, are said to
be linked.
◉ Independent assortment. Answer: During metaphase I of meiosis,
the arrangement of one pair of homologous chromosomes on the
equator of the spindle is independent of the arrangement of any
,other pair of chromosomes. A key event that produces GENETIC
VARIATION in gametes.
◉ Crossing over. Answer: Where chromatids twist around each
other and exchange genetic material. Happens during prophase I of
meiosis which increases the amount of GENETIC VARIATION in
gametes by producing new combination of alleles.
◉ Carrier. Answer: Individual who has an allele, often for a disease,
which is not expressed in the phenotype i.e. they are heterozygous.
◉ True breeding. Answer: Individuals that are true breeding are
homozygous for a particular characteristic or trait.
◉ Epistasis. Answer: A type of gene interaction, where the allele of
one gene masks the effect of the allele of a different gene.
◉ Hemizygous. Answer: Having a single copy of a gene instead of the
normal two. For example, if there is heterozygous inheritance of the
sex chromosomes, XY.
◉ Variation. Answer: The range of differences in characteristics
between organisms
, ◉ Phencopy. Answer: When environmental conditions alter the
phenotype to resemble the effects of genotypic change
◉ Discontinuous variation. Answer: Variation where there are 2 or
more distinct categories with no intermediates. Determined by a
small number of genes with little or no environmental influence.
◉ Continuous variation. Answer: Variation where there are two
extremes and all possible intermediate forms. Determined by many
genes (polygenic) and influenced by the environment.
◉ Etiolation. Answer: When plants grow abnormally long and
spindly because they are not getting enough light.
◉ Chlorosis. Answer: When plants don't produce enough chlorophyll
and turn yellow eg due to lack of magnesium in the soil.
◉ Artificial selection. Answer: When humans select which
individuals in a population to breed together in order to get
desirable traits.
◉ Stabilising selection pressure. Answer: Factor that reduces the
range of phenotypes by selecting against individuals with the
extreme phenotype.
EXAMINATION TEST 2026 QUESTIONS AND
CORRECT SOLUTIONS
◉ Heterozygous. Answer: When an organism has two different
alleles of the same gene.
◉ Genotype. Answer: Description of an organism's alleles.
◉ Phenotype. Answer: Characteristics of an organism as a result of
the expression of its genotype and the environment.
◉ Gene. Answer: Section of a chromosome that codes for a
polypeptide.
◉ Allele. Answer: Alternative version of the same gene.
◉ Gene locus. Answer: Location of a gene on a chromosome.
◉ Dominant allele. Answer: Allele that is always expressed in the
phenotype.
,◉ Recessive allele. Answer: Allele that is only expressed in the
phenotype when there are two of them i.e. in a homozygote.
◉ Codominant allele. Answer: Both alleles are expressed in the
phenotype.
◉ Multiple alleles. Answer: More than 2 alleles for a particular gene.
◉ Sex linkage. Answer: Characteristic or trait controlled by a gene
found on the sex chromosomes.
◉ Homologous chromosomes. Answer: Pair of chromosomes that
carry genes for the same characteristics, at the same gene loci.
◉ Autosome. Answer: Any chromosome that is NOT a sex
chromosome.
◉ Autosomal linkage. Answer: Genes coding for different
characteristics, found on the same non-sex chromosome, are said to
be linked.
◉ Independent assortment. Answer: During metaphase I of meiosis,
the arrangement of one pair of homologous chromosomes on the
equator of the spindle is independent of the arrangement of any
,other pair of chromosomes. A key event that produces GENETIC
VARIATION in gametes.
◉ Crossing over. Answer: Where chromatids twist around each
other and exchange genetic material. Happens during prophase I of
meiosis which increases the amount of GENETIC VARIATION in
gametes by producing new combination of alleles.
◉ Carrier. Answer: Individual who has an allele, often for a disease,
which is not expressed in the phenotype i.e. they are heterozygous.
◉ True breeding. Answer: Individuals that are true breeding are
homozygous for a particular characteristic or trait.
◉ Epistasis. Answer: A type of gene interaction, where the allele of
one gene masks the effect of the allele of a different gene.
◉ Hemizygous. Answer: Having a single copy of a gene instead of the
normal two. For example, if there is heterozygous inheritance of the
sex chromosomes, XY.
◉ Variation. Answer: The range of differences in characteristics
between organisms
, ◉ Phencopy. Answer: When environmental conditions alter the
phenotype to resemble the effects of genotypic change
◉ Discontinuous variation. Answer: Variation where there are 2 or
more distinct categories with no intermediates. Determined by a
small number of genes with little or no environmental influence.
◉ Continuous variation. Answer: Variation where there are two
extremes and all possible intermediate forms. Determined by many
genes (polygenic) and influenced by the environment.
◉ Etiolation. Answer: When plants grow abnormally long and
spindly because they are not getting enough light.
◉ Chlorosis. Answer: When plants don't produce enough chlorophyll
and turn yellow eg due to lack of magnesium in the soil.
◉ Artificial selection. Answer: When humans select which
individuals in a population to breed together in order to get
desirable traits.
◉ Stabilising selection pressure. Answer: Factor that reduces the
range of phenotypes by selecting against individuals with the
extreme phenotype.
