2017

Question 1

Suggest why it was not appropriate to estimate the number of jaguars using the
capture-recapture technique.

Answer 1

estimate will be inaccurate (because of low numbers)
dangerous (for collector or jaguar)
the technique only works well with large populations

Question 2

Suggest and explain one reason, other than epistasis, why the phenotype ratio might
not be 9 : 3 : 3 : 1.

(2)

Answer 2

(autosomal) linkage 
(both) genes / alleles , occur on same , chromosome / autosome / chromatid 

no independent assortment 
(so) alleles , inherited together / end up in same
gamete 

Question 3

The yellow colour in peas is the result of an enzyme that breaks down chlorophyll, which is
green.
* The Y allele codes for the production of an enzyme that breaks down chlorophyll.
* The y allele is the result of a mutation in the Y allele.
* The y allele codes for an inactive form of this enzyme.
(i)* Outline how the Y allele codes for the production of this enzyme and explain why the y
allele codes for an enzyme with a different primary structure.

Answer 3

Genetic code (G)
 DNA base sequence codes for amino acid
sequence
 reference to mRNA base sequence
 triplet code / 3 bases = 1 amino acid
 degenerate code
 substitution could result in same amino acid
Transcription (C)
 transcription then translation
 complementary base pairing
 synthesis of mRNA strand
 role of RNA polymerase
Translation (L)
 mRNA binds to ribosome
 tRNA binds to mRNA
 tRNA brings specific amino acid
 mRNA translated into polypeptide
Effect of y allele (M)
 substitution / frame-shift
 different base sequence of DNA
 different mRNA codon
 different tRNA anticodon
 tRNA brings different amino acid
 different sequence of amino acids
 amino acid sequence is primary structure

Question 4

With reference to the proteins coded for by the seed colour gene, explain why the y
allele is recessive.

Answer 4

(active) enzyme / protein / product , will still be synthesized
even if you only have one Y allele

Question 5

Potatoes are susceptible to infection by a pathogen called Phytophthora infestans, which causes a
disease known as potato late blight. The most visible sign of the disease is a brown discolouration
of the leaves.
Some varieties of potato are resistant to infection by P� infestans�
(a) State two ways in which an individual S� tuberosum plant could respond to infection by P�
infestans�

Answer 5

production / AW of , callose 
release / production , of (named / toxic) chemical 
leaf drop / abscission 
necrosis 

Question 6

why it is important to use clones in an investigation

Answer 6

no , genetic variation 
control (more) variables 
increases validity 

Question 7

The base sequences of homeobox genes in humans and chimpanzees are almost
identical.
What conclusions about the evolutionary relationship between humans and chimpanzees
can be drawn from this piece of evidence?

Answer 7

no / little , because , homeobox genes / they , are highly
conserved (within animal kingdom) 
(only) that humans and chimpanzees , belong to the same
kingdom / are animals 

Question 8

differences between the structures of lactose and
maltose

Answer 8

Lactose
one glucose , one galactose monomer
contains) beta / β-glucose
β-glycosidic bond
sugars in opposing orientation / flipped

Maltose
both monomers are glucose
(contains) alpha / αglucose
α-glycosidic bond
both (monomers) in same direction

Question 9

Explain how the structure of galactose allows it to be used as a respiratory substrate

Answer 9

bonds contain energy
(bonds) can be broken by (respiratory) enzymes
soluble so , can move (within cell)
H / OH , (groups) can form H bonds with water / allow
solubility

Question 10

A colorimeter can be used to measure the concentration of lactose.
The colorimeter first needs to be calibrated.
Describe how a method that uses Benedict’s reagent and a colorimeter could be calibrated to
measure the concentration of lactose in an unknown sample.

Answer 10

zero the colorimeter / set to zero
using blank
use known concentrations (of lactose)
(produce) serial / series , dilutions
construct calibration curve
test unknown sample (using the same method)
use / read from , graph / calibration curve , to determine
(unknown) concentration

Question 11

Many individual bacteria are not transformed successfully during this procedure.
Explain how scientists can determine the success of step D in this procedure.
step d is when the genetically modified bacteria with the desired gene is inserted back in

Answer 11

use of marker (gene) 
(genes for) fluorescence / colour change 
(examine fluorescence under) UV , light / radiation 
antibiotic resistance (gene) 
(then) grow on agar containing antibiotic 