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© James Torrance, James Fullarton, Clare Marsh, James Simms, Caroline Stevenson 2015

First published in 2015 by

Hodder Gibson, an imprint of Hodder Education,

An Hachette UK Company,

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Impression number |     5        4        3        2        1
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Illustrations by James Torrance

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Printed in Slovenia

A catalogue record for this title is available from the British Library

ISBN: 978 1 4718 4742 4
eISBN: 978 1 4718 4727 1

1 Structure of DNA

Matching test

Match the terms in list X with their descriptions in list Y.

list X

  1 3’ end

  2 5’ end

  3 adenosine (A)

  4 antiparallel

  5 cytosine (C)

  6 deoxyribose

  7 DNA

  8 double helix

  9 eukaryote

10 genotype

11 guanine (G)

12 nucleotide

13 plasmid

14 prokaryote

15 sugar–phosphate backbone

16 thymine (T)

list Y

a) advanced organism such as a plant or animal

b) simple organism such as a bacterium

c) small ring of DNA present in prokaryotes

d) phosphate end of DNA strand to which nucleotides cannot be added

e) deoxyribose end of DNA strand to which nucleotides can be added

f) basic unit of which nucleic acids are composed

g) the relationship between two strands of DNA with their sugar-phosphate backbones running in opposite directions

h) supporting structure of nucleic acid molecule formed by bonding between adjacent nucleotides

i) sugar present in DNA

j) base present in DNA which is complementary to guanine

k) base present in DNA which is complementary to adenine

l) base present in DNA which is complementary to cytosine

m) base present in DNA which is complementary to thymine

n) nucleic acid present in linear and circular chromosomes

o) genetic constitution of an organism determined by the sequence of bases in its DNA

p) two-stranded molecule of DNA wound into a spiral

Multiple choice test

Choose the ONE correct answer to each of the following multiple choice questions.

  1 The structure of one nucleotide is shown below.

      Which of the following diagrams shows two nucleotides correctly joined together?

  2 If a double-stranded DNA molecule is 50 000 base pairs long, how many nucleotides does it contain?

    A 25 000

    B 50 000

    C 100 000

    D 200 000

  3 If a DNA molecule contains 10 000 base molecules of which 18% are thymine, then the number of cytosine molecules present is

    A 1800

    B 3200

    C 6400

    D 8200

  4 If a DNA molecule contains 4000 base molecules and 1200 of these are adenine, then the percentage number of guanine bases present in the molecule is

    A 12

    B 20

    C 28

    D 30

  5 The following diagram shows part of one strand of a DNA molecule.

      Which of the strands in the diagram below is the complement of the original strand?

  6 The diagram below shows the stages that occur in an actively dividing mammalian cell.

    The drug aminopterin inhibits thymine production. When this drug is added to a culture of actively dividing cells, after 16 hours most of the cells are found to have been UNABLE to complete one of the stages in the cycle. This stage is number

    A 1

    B 2

    C 3

    D 4

  7 The diagram below represents Griffith’s bacterial transformation experiment.

    Which syringe in the following diagram would NOT lead to the death of a mouse?

  8 Applying Chargaff’s rules relating to the number of different bases in a DNA sample, which of the following is correct?

    A T = C

    B G = A

    C C + G = T + A

    D T + C = G + A

  9 A bacterial cell is

    A eukaryotic and all of its DNA is circular.

    C eukaryotic and all of its DNA is linear.

    B prokaryotic and all of its DNA is circular.

    D prokaryotic and all of its DNA is linear.

10 The accompanying diagram shows four stages employed during the separation of DNA by gel electrophoresis. The order in which they would be carried out is

    A 4,2,1,3

    B 2,4,3,1

    C 2,4,1,3

    D 4,2,3,1

2 Replication of DNA

Matching test

Match the terms in list X with their descriptions in list Y.

list X

  1 amplification

  2 complementary

  3 DNA

  4 DNA polymerase

  5 ligase

  6 polymerase chain reaction (PCR)

  7 primer

  8 replication

  9 specific target sequence

10 template strand

list Y

a) complex molecule present in chromosomes which stores genetic information

b) term used to refer to the unwound strand of DNA to be replicated

c) the relationship between two members of a base pair able to join by hydrogen bonding

d) increase in number of copies of a DNA molecule by PCR

e) process by which a molecule of DNA reproduces itself

f) enzyme required to promote DNA replication

g) laboratory technique used to create many copies of a piece of DNA

h) enzyme that joins replicated DNA fragments into a complete strand

i) short sequence of nucleotides needed by DNA polymerase to begin replication of DNA

j) region at the end of a DNA strand complementary to a primer

Multiple choice test

Choose the ONE correct answer to each of the following multiple choice questions.

Questions 1, 2, and 3 refer to the following diagram which shows the formation of the lagging strand of DNA during replication.

  1 Which structure is ligase?

  2 Which structure is DNA polymerase?

  3 Which structure is part of a replication fork?

  4 The following diagram shows a portion of DNA undergoing semi-conservative replication.

    If the products undergo a further round of semi-conservative replication, which of the sets of products shown in the diagram below would be the result?

  5 The steps given in the following list are involved in the first cycle of the PCR technique.

    1  Heat-tolerant DNA polymerase adds nucleotides to the primers.

    2  DNA to be amplified is heated to separate its two strands.

    3  Two identical copies of the original DNA molecule are formed.

    4  Following cooling, each primer binds to its target DNA sequence.

    Their correct sequence is

    A 1,4,3,2

    B 2,1,3,4

    C 2,4,1,3

    D 4,2,3,1

  6 The following diagram represents the early stages of the first cycle of PCR.

    Which of the answers in the diagram below shows the correct outcome at the end of the first cycle?

  7 Starting with a single DNA molecule, how many DNA molecules would be present after 8 cycles of the PCR procedure?

    A 16

    B 64

    C 256

    D 512

Questions 8 and 9 refer to the information in Figure 2.6 which shows three types of DNA molecule._________represents a single DNA strand labelled with ¹⁵N (a heavy isotope of nitrogen) and - - - - - represents a single DNA strand labelled with ¹⁴N (a common isotope of nitrogen). A mixture of these can be separated as indicated.

  8 If bacteria, grown for many generations in ¹⁵N, are transferred to ¹⁴N medium for one generation’s growth, which of the following will result on extracting and centrifuging their DNA?

  9 Imagine that a molecule of heavy DNA is replicated for two successive generations in ¹⁴N medium. Which line in the following table shows the DNA molecules that would be formed?

10 Evolutionary relationships between different groups of plants can be investigated following amplification of their DNA by

    A gel electrophoresis.

    B precipitation in alcohol.

    C degradation by protease.

    D polymerase chain reaction.