Biology 9700/43 — October/November 2013

Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme

questions

100

marks

120

minutes

Topics Classification, Biodiversity and Conservation · Control and Coordination · Inheritance · Selection and Evolution · Energy and Respiration · (outdated) Aspects of Human Reproduction · +4 more

Q1InheritanceFree sample

A mutation in a gene in the fruit fly, Drosophila melanogaster, gives rise to white-eyed flies instead of the normal red-eyed flies. The allele for red eyes ( $R$ ) is dominant to the allele for white eyes ( $r$ ).

A student crossed a red-eyed fly with a white-eyed fly.

The results are shown in Table 1.1.

Table 1.1

phenotype of fly	number of offspring
red-eyed female	54
red-eyed male	0
white-eyed female	0
white-eyed male	46

(a)

In Drosophila, males possess two different sex chromosomes, X and Y, as in humans.

Complete the genetic diagram below to show how the results in Table 1.1 could have been produced.

Fig. 1.1

(b)

(i)

The chi-squared ( $\chi^2$ ) test can be used to analyse the results in Table 1.1.

The expected ratio of red-eyed females to white-eyed males is $1:1$ .

Complete Table 1.2 and use this to calculate a value for chi-squared ( $\chi^2$ ).

\chi^2 = \sum \frac{(O-E)^2}{E}

$v = n-1$

key

$\sum$ = sum of
$v$ = degrees of freedom
$n$ = number of classes
$O$ = observed value
$E$ = expected value

Table 1.2

phenotype of fly	O	E	O-E	$(O-E)^2$	$\frac{(O-E)^2}{E}$
red-eyed female
white-eyed male

$\chi^2$ = ______

(ii)

Use your calculated value of $\chi^2$ and the table of probabilities below, to test the significance of the difference between observed and expected results.

degrees of freedom	probability
	0.90	0.50	0.10	0.05
1	0.02	0.45	2.71	3.84
2	0.21	1.39	4.61	5.99

The rest of this paper

10 more questions

Q2Selection and Evolution15M
Q3Energy and Respiration7M
Q4(outdated) Aspects of Human Reproduction15M
Q5Selection and Evolution · Classification, Biodiversity and Conservation · Inheritance10M
Q6Control and Coordination · Classification, Biodiversity and Conservation10M
Q7Photosynthesis8M
Q8Classification, Biodiversity and Conservation5M
Q9Control and Coordination7M
Q10Genetic Technology15M
Q11Homeostasis · Control and Coordination · (outdated) Biotechnology15M

Loading the full paper…