Paper 2 2023

Question 1

Answer 1

• swapping of {alleles / genetic material} (1)
• between non-sister chromatids (1)
• of a {homologous pair of chromosomes/
bivalent} (1)
• resulting in different combinations of
alleles (1)

Question 2

Answer 2

• a group of genes / a section of DNA (1)
• (controlled by a single) {operator/
promotor} / that are transcribed together
(1)

Question 3

Answer 3

• lactose allows the lac operon to function (1)
• RNA polymerase can now bind to promoter
(region) / repressor (molecule) no longer
binds to operator (1)
• allowing {transcription / mRNA to be
synthesised} (1)
• so enzymes involved in {metabolising /
breaking down} lactose are made (1)

Question 4

Answer 4

• selecting one embryo over another / loss of a
potential life (1)
• risk of identifying other conditions / selecting
for other characteristics (1)
• {costly / emotional strain } as not always
accurate (1)

Question 5

Answer 5

• (produces) sticky mucus (1)
• (which) { blocks / reduces } flow of {pancreatic
juice / enzyme
from pancreas } (1)
• (so) reducing digestion (1)
• {blocks / reduces } flow of bile (1)

Question 6

Answer 6

Similarity
• (both) look for any genetic condition (so
parents can make informed decisions) (1)
Differences
• PGD before implantation / amniocentesis
after implantation (1)
• (increased) risk of miscarriage with
amniocentesis (1)
• embryo tested in PGD / amniotic fluid
tested in amniocentesis (1)

Question 7

Answer 7

• doubling of the DNA (1)
• with each original DNA strand acting as a
template (onto which a new strand is
formed) (1)
• (so) (each double-stranded) DNA formed
contains one original strand of DNA and
one new strand of DNA (1)

Question 8

Answer 8

• less thromboplastin (released from fewer
platelets) (1)
• (so less/slower) prothrombin converted to
thrombin (1)
• (so less/slower) {fibrinogen converted to
fibrin / fibrin formed} (1)
• fewer platelets to be trapped in the fibrin
mesh (1)

Question 9

Answer 9

• predominance of {type I / slow twitch} muscle fibres (1)
• (long duration activity so) require muscle fibres that are slow to
fatigue (1)
• low level of anaerobic respiration reduces lactic acid build up (1)
• {ATP needed over a longer time frame / (overall) more ATP
needed} so provided by (more efficient process) {aerobic
respiration / oxidative phosphorylation / chemiosmosis} (1)
• high mitochondria concentration for (more) aerobic respiration
(1)
• {type II / fast twitch} muscle fibre allows runner to run faster
(towards the end) (1)

Question 10

Answer 10

• genetic modification has {only occurred
in cells of the eye / not occurred in
gametes} (1)
• (person treated) has gametes with the
allele for the condition (1)
• {partner / other gamete} also supplies a
recessive allele (1)
• mutation occurs in gene of offspring (1)

Question 11

Answer 11

Question 12

Answer 12

• this (mutation) leads to a different
{primary structure (of protein) / amino
acid sequence} (1)
• for the protein opsin (1)
• (so) a {different / misfolded} tertiary
structure of protein / altered shape of the
protein (1)
ALLOW different R group interactions
ALLOW therefore less retinal binding to the
protein
• (resulting in) more light of 280nm being
absorbed (than 500nm) (1)

Question 13

Answer 13

• increased red light (due to a long day / short
night) / limited exposure to far-red light (1)
• phytochrome red converted to phytochrome
far-red in the day / little conversion of far
red form to red form during the (short) night
(1)
• {accumulation / high concentration} of
phytochrome far red stimulates flowering (1)

Question 14

Answer 14

• grow in conditions with different periods of
time in light (per day) / range of hours in light
(1)
• control a relevant abiotic factor (1)
• record whether plants flower or not (1)