cellular control answers f215

8/12/2019 Cellular Control Answers F215

1/33

1. (a) (i) genelength of DNA;codes for a (specific), polypeptide / protein / RNA; max 1

allele

alternative form of a gene;found at a, locus / particular position on, a chromosome; max 1

(ii) assume allele refers to coat colour allele

(coat colour) gene / alleles, only on chromosome;Ano (coat colour), gene / allele, on Y chromosome

male cats, ! / only have one chromosome;males have only one (coat colour) allele / cannot have t"o (coat colour)

alleles;need #lac$ and orange alleles for tortoiseshell colour; %

(#) parental genotypes &r&r' &"&";gametes &

r, &

";

F1genotypes and phenotypes 1 mark:

1genotypes (all) &

r&

"

1phenotypes (all) pin$;

F2genotypes and phenotypes 1 mark

gametes &r, &

"&

r, &

";

%genotypes &

r&

r&

r&

"&

r&

"&

"&

"

%phenotypes red pin$ (pin$) "hite;

%ratio 1%1;

accept other symbols if key given*accept r and as symbols ithout key! +

(c) (i) +; 1-.; +; -

(ii) .*1- 0 .*.. 0 .*.+1; (or other suitable orking).*%.+ 2 .*%.;

2 marks for correct value if no orking shonecf for both marks but calculated value must be to three decimal

places %

(iii) support, figure lo"er than *331 / figure lo"er than critical value;

R"support# on its on!

ecf applies if value in (ii) is incorrect 1[16]

The Henrietta Barnett School 1


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2. parental genotypes Rr4# ' Rr## ;

gametes R4 R# r4 r# R# r# ;

offspring genotypes RR4# Rr4# (Rr4#) Rr## RR## (Rr##) rr4# rr## ;

offspring phenotypes rough #lac$ rough "hite smooth #lac$ smooth "hite ;

e$pected ratio - - 1 1 ;accept correct gametes, offspring genotypes and offspring phenotypes in

%unnett s&uare

use ecf e$cept for ratioRejectthe ratio ' : ' : 2 : 2

ratio not a stand alone mark there must be some correct orking to support it[5]

3. DNA codes for ,protein / polypeptide;

transcription and translation (or descri#ed);en5yme is glo#ular (protein);

- #ases 1 amino acid;

se6uence of ,#ases / triplets ,determines , se6uence of amino acids /primary structure;

coiling / helix / 7pleated sheet / particular secondary structure;

determines pro8ecting side groups;folding / #onding ,for tertiary structure;-7D structure is tertiary structure;A9:; e*g* ref* active site related to shape

% or more genes produce 6uaternary structure max[4]

4. (a) provides sites for #inding ;

ref to, spindle fi#res / microtu#ules ;

ref to genes #eing spaced out along chromosome ;

places to #rea$ and re8oin (during meiotic division) ; Achiasmata formation


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5. 1 proteins needed for repair / AB ;

2 more transcription of, DNA / genes ;

3 more translation ;

4 protein synthesis ;

5 named protein ; e*g* actin / myosin / troponin / tropomyosinignore all refs to muscle contraction

6 more aero#ic respiration ;

7 so more, energy released / A>: produced ;

8 (energy re6uired for) condensation / ana#olic, reactions ;

9 (energy re6uired for) formation of peptide #onds ;

10 (energy re6uired for) formation of extra mRNA ; max [5]

6. 1 #oth result from changes in allele fre6uencies ;

2 selective #reeding often faster than evolution / ora ;

3 #oth re6uire selection of parents ;

4 to pass alleles to offspring ;

5 selective #reeding involves artificial selection ;

6 v* evolution involves natural selection ;

7 man selective agent in selective #reeding ;

8 v* "hole environment selective agent in, natural selection / evolution ;

9 selective #reeding for #enefit of man ;

10 may #e detrimental to organism / e*g* detriment ;

11 v* fitness for environment ;

12 single / fe", trait(s) in selective #reeding ;

13 v* "hole, phenotype / genotype ;

14 A9: ;

15 A9: ; max

QWC legible text with acc!ate "#elli$g, #$ctati%$ a$& g!a''a!; 1[9]

7. (i) mutation ;

chance / random / preexisting ;

insecticide acts as selective, agent / pressure ;

suscepti#les die / resistants survive ;

resistants pass, mutation / allele, to offspring ; Agene max -

(ii) mos6uito is vector ; Acarrier



4/33

o#ligatory / AB ;

part of life cycle is in mos6uito ;

not $illed #y insecticide ; max %[5]



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8. (a) (i) Aa## 7 pin$ ;

aa44 7 green ; %

(ii) (dominant) epistasis ;

ref to, epistatic / hypostatic, gene ;

ref to, promoter / gene s"itching ;increased, transcription / expression ; max -

A9: ; en5yme to alter pigment / change structure of pigment /ma$e more pigment / complementary action

(#) (i) parents (Aa4#) red spines ' (aa##) green spines ;

gametes A4 A# a4 a# ' a# ;Afrom %unnett s&uare

offspring genotypes ; ; minus 1 for each of first to mistakes

phenotypes related to genotypes ; Akey

ratio 1 red spines 1 pin$ spines % green spines ; max

gametes * b a* ab

ab a*b abb aa*b aabb

red spines pink spines green spines green spines

(ii) many Aa4# and aa## ;

ref 1 1 ratio of these ;

ref lin$age ;

ref parental types ;

fe" Aa## and aa4# ;

ref 1 1 ratio of these ;

ref recom#inants ;

ref crossing over ;

many red and green spined ;

fe" / no, pin$ spined ;

1 1 green red / more green than red ;

ref proportions depend on ho" close, loci / genes, are ; max

[15]

9. (a) R RR

R7 lo", do not have enough vitamin C in diet / ref to figures ;

RRR

7 high, ("arfarin resistant) and have enough vitamin C

/ ref to figures ;

RR

7 lo" , "ill #e $illed #y "arfarin / ref to effects of "arfarin ;

+f &uote probabilities for survival less than -. is lo and over -. is high -



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(#) (i) mutation / named mutation ;

change in DNA #ase se6uence ; max 1

(ii) variation "ithin population ;

some individuals produce en5yme not suscepti#le to "arfarin ;

these individuals survive / selective advantage ;reproduce / #reed ;

pass, resistance / advantageous allele , to offspring ; Rgene

those "ithout resistance die ;

ref to selective pressure of "arfarin ; max

(c) does not directly involve humans ;

environment selects individuals that "ill reproduce ; max 1

(d) resistant allele / RR, "ill decrease a$&, suscepti#le allele / R

, "ill

increase ;

RRR

Rat a disadvantage due to vitamin C re6uirements / R

R

at

an advantage due to "arfarin #eing removed ;

Afre6uencies of #oth alleles "ill stay the same ;

must be linked to second statement

no longer any selective pressure / no directional selection ; max %[12]

10. 1 ref to operon ;

2 normally repressor su#stance #ound to operator ;

3 prevents RNA polymerase #inding (at promoter) / prevents transcription ;

4 lactose #inds to repressor ;

5 changes shape of protein molecule ;

6 una#le to #ind (to operator) ;

7 RNA polymerase #inds (at promoter) / transcription occurs/ genes s"itched on ;

8 production of lactose permease ;

9 production of #eta 2 galactosidase ;[5]



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11. (i) length of DNA ;

codes for a (specific), polypeptide / protein / RNA ;

found at a, locus / particular position on, a chromosome ; %

variety / form of a gene ; Rtype of gene Atype of a gene 1

(ii) assume the allele coat colour allele(coat colour) gene / alleles, only on chromosome ;

Ano (coat colour), gene / allele, on ! chromosome

male cats, ! / only have one chromosome ;

(males have) only one (coat colour) allele / cannot have t"o(coat colour) alleles ;

need #lac$ and orange alleles for tortoiseshell colour ; max %[5]

12. (a) 1 % 1 ; 1

(#) 1 ref to, codominant / e6ually dominant (alleles) ;

Aincomplete dominance #ut Rgenes as alternative to alleles

2 appropriate sym#ols for t"o codominant alleles ; eg ?1and ?

%

Ra capital and a lo"er case sym#ol or t"o different letterssuch as ? and !

3 parent plant sho"n or stated to #e hetero5ygous ; Aif it is explainedthat any sunny plant is hetero5ygous

4 gamete genotypes sho"n appropriately ;

5 correct offspring genotypes ;

6 the


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9 chi s6uared test could #e used ;

10 A9: ; max -



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(d) credit ora here

Achloroplast as alternative to chlorophyll

yello" seedlings have, no / very little, chlorophyll ;

cannot photosynthesise ;

die "hen, energy reserve / car#ohydrate (accept food), in seed isexhausted ;

dar$ green gro" more #ecause they have more chlorophyll(than the yello"7green) ;

so dar$ green have more, photosynthetic products / named product ;

ref to competition #et"een the seedlings ;

ref to, selection / selective advantage ; max -[12]

13. (i) economy of, materials / resources ;

economy of energy ;

saves unnecessary, transcription / translation ; % max

(ii) random / chance / preexisting, mutation (for resistance) ;

resistants survive / suscepti#les die ;

natural selection ;

insecticide selective agent ;Aselective pressure

resistants pass, mutation / allele for resistance, to offspring ; Rgenefre6uency of, mutation / allele for resistance, increases in population ; max

[7]

14. (i) RNA(i) com#ines "ith mRNA ;

e*g* of #ase pairing (#ut not >) A7@ / ?7& ;

stops translation ;

ref to stops mRNA com#ining "ith ri#osomes ;

stops protein synthesis ; max -

(ii) chemicals / en5ymes in, mouth / toothpaste / #acteria ;

denature / degrade, RNA ;

RNA not normally ta$en up #y #acterial cells ;

short life of RNA ;

RNA not replicated in #acteria "hen #acteria reproduce ;

toothpaste in mouth only for short time ;

A9: ;

A9: ; e*g* "ashed a"ay #y saliva max %[5]



10/33



11/33

15. plant signal used #y ear"orms ;

)s"itches on gene coding for *;

can then #rea$ do"n insecticide ;

effect on transcription ; (' *)

reduces mortality ;even in a#sence of insecticide ;

in a#sence of ), mortality, high / c* F ;

ref to comparative figures ;

e*g* to F / almost halved, in presence of insecticide

1+ to F / more than halved, in a#sence of insecticide

slight expression of *in a#sence of )caused #y insecticide ; max[4]

16. increase in use of, ? crop / ?G crop / 4t cotton ;

no / less, insecticide needed ;

reduced num#er of cases of pesticide poisoning ;

ref to figures (e*g* #y x *) ;

reduced cost (insecticide) ;

ref to figures (e*g* #y .*+% @H $g71

/ ' 1*-) ;

ref to limitations of survey ;

A9: ;

Areverse arguments max [4]

17. (a) (i) Aa(("hite ;

aa((#lac$ ;

Aabb"hite ;

aabb#ro"n ;

(ii) (dominant) epistasis ; 1

(iii) codes for inhi#itor ;

protein ;

#loc$s transcription (of allele coding for pigment) ;

ref to, regulator / promoter ;

#loc$s en5yme (producing pigment) ;

A9: ; e*g* detail max -



12/33

(#) (i) Aa4# ' Aa4# / Aa4# ' Aa## ;

#oth must have A #ecause they are "hite ;

I #oth must, have a / not #e homo5ygous AA, #ecause some$ittens coloured ;

I #oth must have # to give #ro"n $ittens ;J "must be hetero0ygous at both loci# 1 only

at least one / one or #oth, must have 4 to give #lac$ $ittens ;

credit ref to :unnett s6uare sho"ing genotypes ;

credit ref to :unnett s6uare sho"ing phenotypes ; max

(ii) Aa4# ' Aa4# 1% "hite - #lac$ 1 #ro"n ;;

Aa4# ' Aa## + "hite 1 #lac$ 1 #ro"n ;; max %[15]

18. A/


13/33



14/33

(c) (i) #inds RNA polymerase ;

allo"s, transcription / production of mRNA ;

s"itches gene on / allo"s gene expression ; % max

(ii) (protect against) more than one, strain / disease / pathogen / AB ;

stronger immune response ;less li$ely mutant form "ill escape immune response / AB ;

A9: ; cheaper / reduces num#er of vaccinations % max

(iii) ?olgi modifies protein / polypeptide / AB ;

forms glycoproteins / add sugars orcar#ohydrate ;

?olgi forms vesicles ;

incorporated into cell mem#rane ; Rexocytosis

A9: ; % max

(d) cells that take up vaccine might

1 function less "ell ;

2 #e $illed #y immune system / trigger auto7immune response ;

3 have genes disrupted / mutation ;

4 ne" gene might #e inherited / AB ;

5 plasmid could enter #acteria ;

6 super#ug / create ne" disease / AB ;

7 effects un$no"n / ne" technology / no human trials ;8 A9: ; ref ethics, ref irreversi#le - max

[14]

20. (i) (334 / macrophages)(siRNAs continue to "or$) in long7lived cells ;only one treatment needed for macrophages / &&R ;(siRNAs diluted) as lymphocytes divide ; orarepeat treatments needed for, lymphocytes / &D ; %

(ii) (334)#ecause no essential function in #ody / a#sence not a pro#lem ; 1

[3]



15/33

21. (i) P, , :, N, , R ; 1

(ii) accept correct names of stages

P ; Aprophase 1

; Aanaphase %

P / ; Aprophase 1 / metaphase 1 ; Ametaphase 1

R ; Atelophase %

(iii) DNA replication ;

synthesis of proteins / named protein ; Atranscription / translation

synthesis of mem#rane ;

synthesis of, organelle(s) / named organelle ;

respiration ;

A9: ; e*g* centrioles replicate ; % max [8]

22. (a) estimate of role of genotype in phenotypic variation / AB ;

herita#ility L 9?

/ 9:;

"hen herita#ility high much of variation is, genetic / not environmental/ ora ;

high herita#ility "ill result in successful selective #reeding / ora ; % max

(#) single / ma8or / endelian, gene ;

large effect ;

little environmental effect ;

dominant allele > expressed in homo7 and hetero5ygote ;

not polygenic ;

not additive ;

discontinuous variation / not continuous variation ;

6ualitative / not 6uantitative ; % max

(c) (i) triplet of #ases that does not code for an amino acid ;

A>> / A>& / A&> ;

code to mar$ end of gene ;

code to stop transcription / ref to disengagement RNA polymerase ; % max

(ii) transcription halted early / AB ;

protein "ill, #e smaller / have fe"er amino acids ;

tertiary structure / -D shape different ;

#inding / affinity, different ;



16/33

protein inactive ; - max

ref to lacoperon ;

(iii) ref to, promoter / operator / / AB , increases num#er of tillers per plant ;

and num#er of #ranches per tiller ;

ref to comparative figures ; % max

(ii) inserted into genome randomly / cannot choose "here it is inserted ;

may #e "ithin a fre6uently expressed gene ;

may #e after an


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10 reproduce ;

11 pass alleles on (to, offspring / next generation) ;

12 ref to sta#ilising selection (in #oth ha#itats) ;

13 ref to other $a'e&selection pressure(s) ;

14 not a very mo#ile population orlittle, immigration / emigration ;

15 separate gene pools descri#ed ;

16 little mutation ta$ing place ; Ano ne" camouflage method over time

17 ha#itat sta#le ;

18 ref to "hy unfavoura#le alleles have not disappeared ;

19 A9: ; e*g* calculated average figures for #oth ha#itats max

QWC clea! well %!ga$i"e& "i$g "#eciali"t te!'" ;

clear and "ell organised and must include mar$ing points and 1[11]



18/33

24. pigmented #irds more li$ely to #e damaged;at all percentages;more damage as percentage of pigmented #irds increases to %-F;more damage as percentage of "hite #irds increases to %F;fall in damage of "hite #irds at, %F/highest percentage; max -

[3]

25. (i) Qndividual % 7 O

! ;

Qndividual 7 h! ;

Qndividual + 7 O

! ;

Qndividual 3 7 O

h;

ma$ 2 if se$ chromosomes not shon

(ii) half / .* / .F / 1 in % ; A11, .. R1% 1

(iii) carriers have, #oth / O and h / dominant and recessive, alleles ; Aarehetero5ygous Rt"o alleles

females have t"o chromosomes / ora ; %[7]

26. (a) (i) @ A & & ? ? A @ @ & A &;;

1 error 1, 2 errors -

allo 1 mark for giving 7 throughout instead of 8

(i!e! 7 3 3 6 6 7 7 3 3 1 mark) %

(ii) transcription / transcri#ed;R transcriptase 1

(#) (i) ) anticodon;R anticodons+ transfer RNA / tRNA; ri#osome / rRNA;- codon;R codons



19/33

(ii) 1 DNA triplet / codon / -/ mRNA triplet,codes forspecific amino acid;

2 order of, triplets / #ases, determines the order of amino acids;

3 tRNA / C, has, corresponding / complementary,triplet / anticodon;

4 (tRNA / C) attached to specific amino acid;

5 activation of amino acid;

6 % (tRNA) #inding sites on the ri#osome;

7 codon and anticodon #ind;Amatch

8 A to @ and & to ?;

9 ad8acent amino acids 8oin;

10 peptide #ond; max

(c) 1 attaches to ri#osome;

2 removes,#ase / portion, of ri#osome;Astops ri#osome assem#ling / changes shape of ri#osome

3 prevents ri#osome,attaching to / reading, mRNA;

4 prevents codons #eing exposed;

5 prevents,tRNA / anticodon,attaching to,mRNA / codon;

6 prevents / inhi#its en5yme responsi#le for,formation ofpeptide lin$ages;

7 A9:;e*g* further detail of any of the a#ove points % max[13]

27. (i) A, (and *; 1

(ii) apply ora throughout

produced #y, sexual reproduction / fusion of gametes / fertilisation ;

ref to random mating ; random fertilisation 2 marks

contain chromosomes from t"o individuals / diploid organisms ;

more alleles ; % max

(iii) Cand are haploid organisms ;

haploid cells have, one set of chromosomes / half the num#er ofchromosomes ;

meiosis re6uires pairing of homologous chromosomes ;

ref to maintaining chromosome num#er "hen gametes fuse / gametesmust #e haploid ; % max

[5]



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28. (a) any to of the folloing

(monomer) not glucose ;

contains nitrogen ;

contains, sulphur ;

A9: ; Rref to #ranching % max

(#) amount of glycoprotein varies (in different cells) ;

(cells carry out) endocytosis to different extents ;

cells have different life spans / example ;

no time for polysaccharide to accumulate in short lived cells ;

num#er / role, of lysosomes not same in all cell types ;

A9: ; 1 max

(c) ith 9unter#s syndrome, lysosomes / vesicles, might be

larger ;

more numerous ;

have different shape ;

stain differently ;

A9: ; e*g* granular cytoplasm 1 max

(d) (i) unaffected parents can have an affected child ; orae*g* -, , / 11, 1%, 1+, 1 ; 1 max

(ii) only males affected ; ora

mothers pass it on ; ora

on the chromosome ;

carrier "omen asymptomatic / dominant normal allele mas$s trait ;

/ 11 / 1 , could #e carriers ; % max

(e) there are only - cases / too small a sample ;mostly female line sho"n ;

A9: ; e*g* pedigree of, - / 1%, not $no"n

progeny of, 1- / 1 / 1, not $no"n 1 max



21/33

(f) drug must act in all cells ;

lysosomes are "ithin cells ;

hard for drug to reach ;

if drug acts as en5yme, polysaccharide on cell mem#ranes may #e #ro$endo"n ;

tissue mechanical support "ould #rea$ do"n ;

A9: ;

A9: ; e*g* no animal model

protein drug digested in gut

rare condition (6ualified), economic argument % max[10]

29. (a) (i) steep increase, for the first 1 7 % hours / till %*% 7 -* (a*u) ; Alinear,steady #ecame constant at, - hours / *- (a*u) ;

if no figs in description, e!g! "rose then constant# aard 1 mark ma$ %

(ii) (increased as) en5yme "or$ing / rate of reaction high / reactionproceeding ;

(increased as) su#strate converted into, drug / product ;

(levelled off / #ecame constant, after the) en5yme, #ecame inactive /"as denatured;

(levelled off / #ecame constant) #ecause product inhi#its, reaction /

en5yme ;Rreferences to en5yme or su#strate #eing used up R> & limiting %

(#) pO ;

degree of mixing ;

en5yme concentration ;

A9: ; e*g* ref to concentration of inhi#itors 1 max

(c) ma$ of 2 marks for predicting ore$plaining/1 concentration of drug higher / AB ;

/2 rate of reaction slo"er / AB ;

/3 may not level off (in time scale sho"n on graph) ;

/4 time ta$en to reach the maximum yield (approximately)dou#les ; (c*f* 1 &)

*1 not denatured ;

*2 adapted to & / optimum / #ody / usual, temperature ;

*3 ref to P1.

of a#out % ;

*4 ref to lo"er $inetic energy / AB ;

*5 ref to G7, collisions / complexes ;



22/33

A9: ; e*g* ref to active site - max

(d) (i) (shaded amino acids) form the active site ;

su#strate may not attach to the active site ;

en5yme7su#strate complex may not #e formed / AB ; 1 max

(ii) and ++ not part of active site ;

hold, active site / - structure / -D structure, in shape ; Astop denaturinghydrogen #onds "ea$ ;

easily #ro$en #y, vi#ration / heat ; ApO

disulphide #ridge strong ;

not #ro$en #y heat ; % max

(e) nucleotide / #ase/ DNA, se6uence codes for, protein / amino acid, se6uence ;

changes DNA ; Achange triplet

ma$es different mRNA ; Achange codon

transcription ;

different tRNAs line up ; Achange anticodon

translation ;

different (amino acid se6uence in), en5yme / protein / polypeptide ; % max[13]

30. (a) penetration of #iofilm difficult ;

ref to diffusion of anti#iotic ;

detail of diffusion ;

larger A of separate #acteria / ora;

does not reach all #acteria in film / ora;

anti#iotic trapped #y film ;

detail of entrapment ;

dead #acteria in film form #arrier ;A9: ; e*g* hori5ontal transmission / con8ugation, easier in #iofilm

A9: ; max

(#) #oth strains have identical sensitivity "hen in suspension ;

to all three anti#iotics ;

#oth, less sensitive / more resistant, "hen in #iofilms (ora) ;

strain 1 much, less sensitive / more resistant ;

comparative figures ;& most effective / AB ;

4 least effective / AB ; max



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(c) mutation ;

random / chance / pre7existing ;

detail of mutation ; e*g* #ase su#stitution, addition, deletion

ref to, selection / selective advantage ;

codes for different, glucan / #iofilm ;

affects all three anti#iotics ;

#loc$s anti#iotic from reaching cells ;

#inds anti#iotics ; max



24/33

(d) hori5ontal transmission ;

(copy of) plasmid ;

via con8ugation ;

detail ; con8ugation tu#e /


25/33

34. (a) linkage(t"o or more) genes / loci, on same chromosome ; Rallelesdo not assort independently (in meiosis) / inherited together ;

crossing over

reciprocal exchange of portions of, chromatids / DNA ; As"apping alleles#et"een (paternal and maternal) homologous chromosomes ; A#ivalent

in prophase Q (of meiosis) ; ma$ 2 max -

(#) anthers removed (#efore maturity) (to produce male sterility) ;male sterilisation ;genetic or, %6 / hormone

pollen transferred #y hand ;plants isolated ;flo"ers #agged (#efore and after pollination) ; max -

(c) (i) R


26/33

35. genetically isolated populations ;allopatric speciation / AB ;ref to genetic drift ;ref to, founder effect / founder population ;loss of alleles / genetic erosion / reduced gene pool / loss of geneticdiversity / AB ;

ref to, disease / population crash ;A9: ; e*g* ref to exposure to different selection pressures max [4]

36. (i) semi7conservative replication ;DNA, polymerase / helicase ;

#rea$s hydrogen #onds #et"een t"o DNA strands / un5ips DNA ;each DNA strand acts as a template / #oth strands copied ;complementary #ase7pairing ("ith free DNA nucleotides) ;sugar7phosphate #ac$#one forms ; % max

(ii) crossing7over ;in prophase ;recom#ination of, non7sister / maternal and paternal, DNA ;A9: ; e*g* matching cuts in DNA

DNA ligase % max

(iii) synapsis / to hold, (homologous) chromosomes / #ivalent, together ;(so close enough) for crossing7over ;so can #e evenly segregated ;A9: ; e*g* to pac$age or support chromosomes,

avoid DNA #rea$ing,easier to move DNA % max

[6]

37. description

D1 chosen male and female mated ;D% ref to desired characteristic / named desired characteristic ;D- ref to AQ ;

D advantage of using AQ ;D offspring inspected and #est mated ;D+ several / many, generations ;D ref to pro#lem in#reeding ;D ref to "ay of minimising in#reeding ;D3 ref to herita#ility ;D1. easier to select for traits "ith high herita#ility / ora ;D11 easier to select for discontinuous variation / ora continuous variation ;D1% ref to polygenes / additive effect ; ma$ ' "describe# marks



27/33

e$planation

G1- selective #reeding involves "hole genomes ;G1 hence other traits follo" selected trait(s) ;G1 ref to lin$age ;G1+ artificial selection ;G1 selection, different from natural selection / for #enefit of humans ;

G1 starter population, small / not representative ;Afounder principle ma$ ; "e$plain# < marks

A9: either D or G mar$ ;e*g* ref to use of, Q9 / surrogate, "ith reason

ref to loss of alleles / genetic erosion max

QWC legible text with acc!ate "#elli$g, #$ctati%$ a$& g!a''a!; 1[9]

38. (i) production of desired changes in phenotype of an organism ;

selection of appropriate alleles / AB ;#y artificial selection ;use as parents / mate, those sho"ing desired phenotype(to larger degree) ; max %

(ii) measure of value of individual=s genotype (for #reeding) ;mate "ith num#er of proven individuals ;assess phenotypes of offspring ; Rgenotypesaverage value ;especially useful for sex7limited traits ; Rsex7lin$ede*g* sex7limited trait ; max

[6]

39. ma$ = from points 1 to

1 limited, food supply / space ;% competition ;- predation ; disease ; reached carrying capacity / death rate L #irth rate ;

marking points 1 linked to keeping population stable

+ individuals sho" variation ; variation due to, com#ination of alleles / mutations ; #est adapted survive / ora ; Asurvival of fittest idea3 reproduce ;1. pass alleles to offspring ;11 fre6uency of favoura#le alleles "ill, increase / #e maintained ; Aora max

[5]



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40. chinchilla &&h

&&h

&&h

&O

&&h

&a;

agouti &A

&A

&A

&&h

&A

&O

&A

&a; %

[2]

41. (i) for #enefit of humans;to improve, trait(s)/named trait;to produce desira#le, phenotype/genotype;to increase num#er of desira#le alleles;to increase homo5ygosity;A9:; max %

(ii) ref* self7pollination;ref* in#reeding;limited gene pool; max %

(iii) ref* different num#ers of chromosomes;hy#rid is -n;sterile;gametes have %% and 11 chromosomes/hy#rid has -- chromosomes;some chromosomes unpaired;failure of meiosis;ref* uneven distri#ution of chromosomes;ref* other #arrier to interspecific cross; max %

[6]

42. (i) ;

;(tic$);;

(ii) discontinuous; Sdo notallo if no reason givenT 1

reason

one, gene/locus; Ama>or/?endelian,genediscrete phenotypes/ora;6ualitative/large effect/little environmental effect; max 1

[6]

43. named characteristic;named environmental factor; (mark first anser only) %

[2]

44. t"o different genes represented in each gamete ie P or 6 and R or r;four correct com#inations ie P and R, P and r, 6 and R, 6 and r; %



29/33

[2]

45. stated advantage;detail; e*g* particular character (not hole phenotype)/can alter one trait

only (ithout affecting background genes)/can add allele fromdifferent ta$on ith hich breeding may not be possible/&uicker

(than the many generations of, selective breeding/backcrossing) %

stated disadvantage;detail; e*g* cannot precisely position insert (so) unknon/unanticipated

effect/may pass to other species (ith unknon/undesirable,

effect)/regarded as ethically undesirable (no market/crop

destroyed by protesters)/cannot breed from 6? (re&uires cloning) %[4]

46. 1 ref to operon;% normally repressor su#stance #ound to operator;- prevents RNA polymerase #inding (at promoter) / prevents

transcription; lactose #inds to repressor; changes shape of protein molecule;+ una#le to #ind (to operator); RNA polymerase #inds (at promoter) / transcription occurs / genes

s"itched on; A9:; e*g* production of lactose permease / production of #eta7

galactosidase; max

[5]

47. deficiency gives resistance to malaria;deficient/resistant, individuals more li$ely to survive;alleles, passed to next generation;natural selection;

presence of%lasmodiumis selection pressure;fre6uency of this allele increases;

phenotype more common in population;A9:; e*g* others more li$ely to die of malaria - max

[3]



30/33

48. gene #an$;source of alleles;for future (selective) #reeding;to counteract, genetic erosion/loss of genetic variation;to counteract, in#reeding/homo5ygosity;to counteract extinction;

for changed conditions;example of changed conditions; e*g* climate/environment/disease/fashionto preserve as yet unidentified, alleles/traits; max

[4]

49. (a) (dominant) epistasis; 1

(#) ref* frame shift;ref* three extra, triplets/amino acids;may introduce stop code so shorter, polypeptide/protein;

may increase length of, polypeptide/protein;may alter, shape/-= structure, of, polypeptide/protein;affects active site;

protein/polypeptide, may lose function;protein/polypeptide, may have different function; max

(c) (i) %arental phenotypes: 5hite @eghorn $ 4ed Aunglefol%arental genotypes: QQ&& x ii&& or QQcc x ii&&;

1genotype Qi&& or Qi&c; %

(ii) - "hite 1 pigmented or 1- "hite - pigmented; 1[8]

50. (i) crossing over; treat chiasma(ta) as neutral 1

(ii) prophase; 1

(iii) have different, alleles/#ase se6uence of DNA;Asister chromatids have same alleles/non sister have different alleles 1

[3]



31/33

51. (i) (parental genotypes) Aa4# ' aa##;

(gametes) A4, A#, a4, a# (all) a#;

(offspring genotypes) Aa4#, Aa##, aa4#, aa##;

(offspring phenotypes) grey #ody/normal "ing, grey #ody/#ent "ing,#lac$ #ody/normal "ing, #lac$ #ody/#ent "ing;

Bse&uence of phenotypes must match genotypes for markT

(phenotypic ratio) 1 1 1 1;

apply ecf!

accept alternative symbols if a key is given, but if no key given ma$ ;

(ii) .,.,.,.; 1

(iii) ("or$ing) .*11% 0 .*-1% 0 .*. 0 .*;L .*3%; A-!C/-!C2/-!C=

2 marks for correct anser ith no orking!

ecf if correctly use rong figures from (ii) %

(iv) yes (but no mark for yes on on)

as calculated figure is smaller than *%;

ecf applies to value calculated in part (iii) 1[9]

52. (a) (i) sympatric; 1

(ii) ranges of t"o species, overlap/close together/AB;no geographical #arrier;ref to #ehavioural/genetic/physiological/pre5ygotic #arrier;correct ref to named area of map; max %

(#) ref to mate selection #y si5e; ie large "ith large or small "ith smallref to monogamy;ref to intermediate si5es, at disadvantage/selected against/ora;

intermediate do not pass on alleles/ora;suggested reason "hy intermediate at disadvantage/ora max -



32/33

(c) female produces a lot of eggs;selects male, that can store lots of eggs/has a large pouch/ora;large males fertilise many eggs/ora;chance of more offspring surviving;

or

large female and small male produce intermediates/ora;

intermediates at disadvantage/ora; max %[8]

53. a change in the genetic material;unpredicta#le / AB;extra detail; e*g* addition / su#stitution / deletion / frame shift / small

part of chromosome / may code for different protein /may code for no protein %

[2]

54. 1 mark ma$ for general effect of mutations:

mutation may give different, amino acid / primary structure;Aref stop codon

some mutations alter, molecular shape / tertiary structure / #inding;

ma$ = for e$plaining data in 7able:

so una#le to, accept / transport, O&-

7;

una#le to #ind A>:;

so increase in acidity / decrease in pO;effect on mucus;effect on en5yme(s) /ref pO optimum of en5yme(s);

poor digestion of, protein / lipid / starch;

A9:; e*g* some mutations, give some transport / have less effect*M --F (of norm) allo"s normal digestive function / K +FSAvery loT does not* max -

[3]

55. allo ma$ for folloing:transcription;DNA un5ips / O #onds #rea$;exposing re6uired, gene / se6uence of #ases;RNA nucleotides align "ith DNA;@ "ith A, A "ith >, & "ith ?, a$&? "ith &;RNA polymerase;mRNA formed (using DNA strand as template);leaves nucleus through pore;



33/33

allo ma$ for folloing:

translation;mRNA attaches to ri#osome;tRNA #rings amino acid (to, ri#osome / mRNA);each tRNA attached to specific amino acid;tRNA #inds to mRNA using complementary, #ase triplet / anticodon;

peptide #ond formed #et"een amino acids;DNA / mRNA, (nucleotide / #ase) se6uence determines se6uence ofamino acids;

A9:; e*g* %, #ase triplets / codons, in ri#osomeA9:; e*g* ref* to start / stop, codons

polysomeslarge and small su#unit in ri#osome

g%0

1.[10]

56. 1 mark per correct ro

@ook for both ticks and crosses!

+f a table consists of ticks D@Y or crosses D@Y, then assume that the blank spaces are the

other symbol!

+f a table consists of ticks, crosses and blanks then the blanks represent no attempt at the

anser!

Nucleotides line up along an exposed DNA strand* ;

>he "hole of the dou#le helix he original DNA molecule is unchanged after the process* ;

Adenine pairs "ith thymine* ;[8]

cellular control answers f215

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