Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
Answers to end-of-chapter questions
Answers to EOCQs
Chapter 5
The mark schemes, suggested answers and
comments that appear in this CD-ROM were written
by the author(s). In examinations, the way marks
would be awarded to answers like these may be
different.
Notes about mark schemes
A or accept indicates an alternative acceptable
answer.
R = reject. This indicates a possible answer that
should be rejected.
; The bold semi-colon indicates the award of 1 mark.
/ This indicates an alternative answer for the same
mark. The alternatives may be separated from the
rest of the answer by commas.
( ) Text in brackets is not required for the mark.
Underlining This is used to indicate essential
word(s) that must be used to get the mark.
AW means ‘alternative wording’. It is used to
indicate that a different wording is acceptable
provided the essential meaning is the same, and is
used where students’ responses are likely to vary
more than usual.
AVP means ‘additional valid point’. This means
accept any additional points given by the student
that are not in the mark scheme, provided they are
relevant. But accept only as many additional points
as indicated by the bold semi-colons, e.g. AVP;;
means award a maximum of 2 extra marks.
ORA means ‘or reverse argument’ and is used when
the same idea could be expressed in the reverse
way. For example: ‘activity increases between pH
2 and pH 5 ORA’ means accept ‘activity decreases
between pH 5 and pH 2’.
max. This indicates the maximum number of marks
that can be given.
1 D; [1]
2 B;[1]
3 D;[1]
4 centrosome is a microtubule organising
centre;
makes spindle during mitosis;
contains two centrioles;
located just outside nucleus;
centriole has 9 triplets of microtubules;
no function (during mitosis);
centromere is region of a chromosome that
holds two 2 chromatids together;
point of attachment for microtubules during
mitosis;
point of attachment of chromatids to
spindle;
AVP; [max. 6]
5 a A anaphase; B prophase; C metaphase;[3]
b Information for this answer can be found in
Figure 5.10 on page 92.
1 mark for each correct summary.[3]
[Total: 6]
6 a i metaphase;[1]
ii prophase drawing shows two single
chromosomes, each with a centromere
(not paired chromatids), ‘randomly’
distributed, surrounded by cell surface
membrane but with no spindle;[1]
b a long and a short chromatid, each with
a centromere, are shown inside each
new nucleus;[1]
c six chromatids about half-way between
equator and each pole (12 chromatids in all);
two long, two short, two hooked in each
direction;
centromere leading for each chromatid;[3]
[Total: 6]
7 a microtubules are made out of tubulin
molecules;
the tubulin molecules stick together in a
particular pattern to form the microtubules,
Cambridge International AS and A Level Biology © Cambridge University Press 2014