Cambridge International A Level Biology Revision Guide

Chapter 5: The mitotic cell cycle
g
As stated in Question 8b, the total length of DNA in the 46 chromosomes of an adult human cell
is 1.8 m. The average adult human contains about 100 trillion cells (100 million million, or 10 14 ).
i What is the total length of DNA in a human? Express your answer in km. [1]
ii How many times would this stretch to the Sun and back?
(Average distance to Sun = 149 600 000 km = about 150 million km = 1.5 × 10 8 km.) [1]
[Total: 18]
9 Which of the following statements are true and which are false?
A Centrosomes are replicated before M phase of the cell cycle begins.
B Sister chromatids contain identical DNA.
C The microtubules attached to a given kinetochore extend to both poles of the spindle.
D Microtubule polymerisation and depolymerisation is a feature of the S phase of the cell cycle.
E Kinetochores are found in the centrosomes.
F Telomeres are the sites of attachment of microtubules during mitosis.
G Sister chromatids remain paired as they line up on the spindle at metaphase.
[1 mark each]
[Total: 7]
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