2020

Question 1

Suggest two other reasons why fruit flies are chosen for research into genes controlling the development of body plan

Answer 1

low cost 
rapid reproduction (rate)
idea that fruit fly genetics / development is well
understood

Question 2

There are some public concerns about the ethics of using mice in these investigations.
Suggest two reasons why mice are chosen as a suitable species for investigation.

Answer 2

low cost / rapid reproduction (rate)
genetics / development , well understood 
(more) similar / AW , to humans 
idea that can show effects are generalisable to more than
one species 

Question 3

Tannase is an enzyme produced by some microorganisms. Tannase is useful in many industrial
applications including food production.
The tannase used in food production can be free in solution or immobilised.
(a) State one method by which tannase could be immobilised.

Answer 3

in , (named) matrix / gel 
adsorption / bonding to (named) carrier 
membrane separation 
cross-linking / covalent bonding 

Question 4

The results suggested that immobilised tannase was more stable over a range of pH
values than free tannase.
Explain why immobilised tannase is more active at pH8 than free tannase.

Answer 4

(immobilised enzymes are) less easily denatured 
shape / tertiary structure , supported / AW (by support
material) 
idea that part of enzyme not fully exposed to pH (8) )

Question 5

Suggest two reasons why using immobilised enzymes in industrial processes could be
cheaper than using free enzymes.

Answer 5

product not contaminated with enzyme 
extraction of , product / enzyme , not needed 
recycling (of enzyme)

Question 6

State one disadvantage of using immobilised enzymes in industrial processes

Answer 6

high(er) , initial / set-up , costs 
fewer exposed active sites 
idea that immobilization method might affect shape of
active site 
idea of leakage

Question 7

The population of students varies from year to year and so cannot be said to be stable.
State two other reasons why it might be inappropriate to use the Hardy–Weinberg
principle to estimate allele frequencies for the results in the table.

Answer 7

(population) not (sufficiently) large 
(population) not randomly mating / not subject to
selection 

Question 8

Suggest why Hydra reproduces asexually when conditions are favourable

Answer 8

genetically identical offspring 
offspring produced , rapidly / in large numbers 
(all) offspring will , find conditions favourable / have
same adaptations

Question 9

When conditions are not favourable, Hydra reproduces sexually. This often happens in the
winter.
Cells in the body wall produce sperms and eggs by meiosis.
Large numbers of sperms are released into the water. These sperms can fertilise eggs from
different individuals. Each egg forms a tough outer coat, and can lie dormant at the bottom of
the water until conditions improve.

Explain how sexual reproduction in Hydra leads to genetic variation in the offspring

Answer 9

AO1.1 Demonstrate knowledge and
understanding of scientific ideas
* genetic variation is the variety of alleles
* offspring have alleles from more than one parent
* random fertilisation
* meiosis produces genetically unique gametes
AO1.2 Demonstrate knowledge and
understanding of scientific processes
* crossing over in prophase 1
* alleles swapped between non-sister chromatids
* base sequence of chromosomes altered
* independent assortment / random segregation
* in metaphase 1
* also relevant in metaphase 2 if crossing over has occurred
AO2.5 Apply knowledge and understanding of
scientific processes in a theoretical context
when handling qualitative data
* the sperm from one Hydra can fertilise an egg from any other individual Hydra
* the two Hydra can have different alleles

Question 10

Complete the table below to show the main differences in structure between glucose and
starch.

Answer 10

Glucose
monomer
monosaccharide
no glycosidic bonds
C6H12O6 / more H and O

starch
polymer
polysaccharide
glycosidic bonds
C6H10O5 / less H and O

Question 11

The nitrogen cycle shares many similarities with the carbon cycle.
Describe the similarities between the nitrogen cycle and the carbon cycle

Answer 11

AO2.5 Apply knowledge and understanding of
scientific processes in a theoretical context when
handling qualitative data
* inorganic gases
o CO2 and N2
* in atmosphere
* elements fixed to organic compounds
o C and N both form proteins /
nucleic acids
* incorporated into plants (producers) then
animals (consumers)
* animals obtain element by feeding on
plants
* decomposing microorganisms
* break down organic macromolecules in
living things
* release inorganic molecules
o carbon dioxide and ammonium
ions
* microorganisms return element to
atmosphere
o CO2 released during
decomposition
o N2 released by denitrifying bacteria

Question 12

what do cytokines do

Answer 12

attract phagocytes