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1. The diagram below shows the general structure of a bacterial cell.

C

A

BD

E

F

Use the letters on the diagram to identify the structures described below.

(i) Contains antibiotic resistance genes which may be transferred to other bacteria.

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(ii) ites of !rotein synthesis.

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(iii) Contains the en"ymes for res!iration.

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(Total 3 marks)

Al-NAjah Private School 1

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2. The bases in a gene code for the synthesis of a !rotein. #ene mutations can influence the

metabolism of an organism.

(a) (i) The diagram below shows the bases on the tem!late strand of D$A in the !art of a

gene that codes for a short se%uence of amino acids in an en"yme.

A A C T A # T T # # C A A # T # # T C A C

Each of the following statements is about this se%uence of bases. For each

statement& !lace a cross in the a!!ro!riate bo' to show whether it is true or false.

Statement True False

This se%uence of bases could be used

as a tem!late during translation

A strand of m$A could be synthesised

using this se%uenceThis se%uence codes for amino acids

during !rotein synthesis

(3)

(ii) $ame and describe the structures where the !oly!e!tide chain of this en"yme

would be synthesised.

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(b) Chlamydomonasis a single*celled !hotosynthetic organism that li+es in well*illuminated

!onds. ,n !o!ulations of Chlamydomonas& a gene mutation occasionally occurs. This

mutation enables Chlamydomonasto ta-e in organic com!ounds !roduced by other

organisms and use them as a source of energy.

(i) E'!lain what is meant by the term gene mutation.

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(ii) A !o!ulation of Chlamydomonaswas found in a !ond in the centre of a de+elo!ing

forest of fast*growing trees. uggest how the allele fre%uency for this mutation

could change as the forest de+elo!s. #i+e reasons for your answer.

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(Total 11 marks)


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3. rotein synthesis in cells in+ol+es molecules of D$A and $A.

(a) The table below describes some features of the molecular structure of D$A and $A.

lace a tic- ( ) in the bo' ne't to each statement to show whether it a!!lies to D$A

only& $A only or to both D$A and $A.

Description DNA only RNA only ot! DNA

an" RNA

olymer formed from a single

strand of nucleotides

entose !resent in the

nucleotides

Adenine& cytosine& guanine

and thymine !resent

$ucleotides lin-ed by!hos!hodiester bonds

(2)

(b) The diagram below shows the se%uence of the lastsi' amino acids in a !rotein molecule.

The t$A anticodon that corres!onds to each amino acid is also shown.

amino acids Alanine/#lutamine/#lycine/As!aragine/roline/0aline

tRNA anticodon CGA GUU CCA UUA GGA CAA

Using this information, explain how each of the following processes leads to thesynthesis of this sequence of amino acids.

(i !he formation of mRNA during transcription in the nucleus

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(3)


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(ii !he translation of mRNA into the sequence of amino acids in a ri"osome

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(3)

(c #uggest why the final triplet of nucleotides, on the strand of mRNA in$ol$ed in thesynthesis of this sequence of amino acids, did not correspond with any anticodonon tRNA.

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(2)(Total 10 marks)

4. !he %NA sequencing of the gene responsi"le for cystic fi"rosis (C& has led to thepossi"ility of genetic screening to identify carriers of the disease. %NA can "e extracted

from cells and cut into fragments using specific en'ymes. !he fragments can then "eseparated "y gel electrophoresis.


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(a Name the type of en'yme used to cut %NA into fragments.

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(1)


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(" %escri"e how the following techniques can "e used to separate the fragments of%NA and allow the faulty gene to "e identified.

Gel electrophoresis

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A gene pro"e

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(6)(Total 7 marks)


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5. An in$estigation was carried out into the mating preferences of cichlid fish from threepopulations (A, and C ta)en from *a)e +alawi. !he fish were all the same species,"ut the males of each population showed distinct physical differences.

+ale fish were separated into different areas of a tan) "y transparent plastic sheets.

!he plastic sheets had holes which allowed any female to enter, "ut pre$ented themales from lea$ing.

!he diagram "elow shows the arrangement of the tan).

T r a n s ! a r e n t

! l a s t i c s h e e t s

1 o l e b i g

e n o u g h

f o r f e m a l e

t o ! a s s

t h r o u g h

2 a l e f i s h F e m a l e f i s h

A

B

C

# l a s s t a n -

&emales from each population were allowed to choose one mate, and their offspringwere collected. !he male parent of the offspring was determined using %NA analysis.

!he ta"le "elow shows the num"er of times mating occurred "etween indi$iduals of thedifferent populations in a range of trials.

Female from population

Male from population A B

A -

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(c #uggest how the data support the hypothesis that population A is the most li)elyto "ecome a separate species.

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(4)(Total 11 marks)

6. &ollowing the introduction of %NA fingerprinting into forensic testing, many people ha$e"een freed from prison as a result of new e$idence pro$ided "y the technique.

(a Gi$e reasons why confidence in the new e$idence was strong enough to ena"lethe release of these prisoners.

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(2)


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(" Gi$e one example of physical e$idence that could "e retained from the originalin$estigation and explain why the sample is suita"le for a %NA test to "e carriedout.

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(2)


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