Download ANSWERS on Inheritance File

Biology Unit 10: Inheritance
1.
(a)
(b)
(i)
Year 11 Higher Level
gametes shown:
X
Y
X
X or X X
correctly constructed lines or Punnet square;
XX
XX
XY XY or XY XY
ANSWERS
X
XX
Y
;
XX ;;
3
(ii)
Probability = ½ / 50/50/ one in two/ 1:1 ;
1
(i)
X chromosome sinks further / is heavier/ (most) X chromosomes are
in layer B; ORA
1
male has just X chromosomes / sperm has no Y chromosome /
male has only one type / same chromosome
so all / most sperm X chromosomes are concentrated
at one point / there / no separation;
2
(ii)
[7]
2.
An explanation to include four from:
1.
radiation causes mutation / eq;
2.
results in new feature / new features arise /
variations naturally present in population / eq;
3.
new feature passed onto offspring / eq;
4.
gives better survival (in offspring) / advantage / selected for /
fittest survive / best adapted survive / eq;
5.
poor features selected against / disadvantaged / die out / eq;
6.
over many generations / takes a long time / eq;
plus one communication mark for using a suitable structure and style
of writing
4
1
[5]
3.
(a)
(b)
reference to alleles / genes / genetics / DNA;
they are different;
Ignore references to dominant / recessive
2
female
XX / two X chromosomes / sex chromosomes the same;
[Accept no Y chromosome]
[Reject the chromosomes are all XX]
1
[3]
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1
Biology Unit 10: Inheritance
Year 11 Higher Level
ANSWERS
4.
(a)
(b)
An explanation to include:
cf is caused by recessive alleles / is a recession condition;
parents are carriers / heterozygous;
An explanation to include two of:
bacteria / micro-organisms are trapped in mucus;
but not brought up / swallowed / killed in stomach acid;
too much mucus hinders action of cilia;
2
2
[4]
5.
(a)
normal
short
1
(b)
Nn
nn;
1
(c)
N
n
n
n;
combinations of genotypes, correctly derived;
if parental genotypes are incorrect, two marks max for Punn
square/diagram
(d)
Nn
nn
1
1
[4]
6.
(a)
only expressed/shown when homozygous/both recessive/both same;;
1
(b)
A
a
A
a ;
AA
Aa
Aa
aa ;
correct derivation;
[correct Punnett square]
1
1
1
(c)
has cystic fibrosis/disease/sufferer/ref to symptons (e.g. excessive mucus/
difficulty breathing);
1
(d)
½, half/ 50/50 / 1 in 2/50%/0.5/1:1/ 2/4;
1
credit any letter except X/Y
[6]
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2
Biology Unit 10: Inheritance
7.
Year 11 Higher Level
ANSWERS
(a)
6;
1
(b)
one long, one middling, one short (chromosome shown as a single line);
1
(c)
meiosis;
REJECT e.g. any spelling involving “t”
1
[3]
8.
An explanation to include four of:
initially most flies susceptible / die;
mutations;
some have resistance / show variation;
this is genetic / inheritable;
differential survival / survival of the fittest;
eventually most flies are resistant;
(reject immunity and acquired characteristics)
[4]
9.
(a)
(b)
(c)
(d)
(i)
polydactylous / has extra digits / toes / fingers / affected;
[Ignore single letter in answer but if genotype given, reject]
1
(ii)
does not have condition / normal / no extra / unaffected;
[Ignore single letter in answer but if genotype given, reject]
1
(i)
sex – male / boy;
phenotype – unaffected / normal / no extra;
[Ignore single letter in answer but if genotype given, reject]
2
(ii)
Dd / heterozygous;
dd / homozygous recessive;
[Deduct 1 mark for each additional incorrect genotype]
2
(iii)
Dd / heterozygous;
1
X (chromosome) from mother/ egg;
Y (chromosome) from father/ sperm;
2
(parents
Dd
dd)
gametes D
d
d
d;
children Dd
Dd
dd
dd;
probability - 50:50 / 1:1 / ½ / equal (chance) / evens / 0.5 / 50% eq;
3
[12]
10.
(a)
phenotype
genotype
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– visible characteristics / alleles expressed / eq;
– genetic make-up / all alleles /
dominant and recessive alleles / eq;
2
3
Biology Unit 10: Inheritance
(b)
(c)
Year 11 Higher Level
ANSWERS
– widening blood capillaries to increase blood flow/
increases heat loss / more blood to skin /
arteriole open / eq;
vasoconstriction – narrowing of blood capillaries to reduce blood flow /
decreases heat loss / more blood to body core /
arteriole closed / eq;
[Reject blood vessel movement once only]
vasodilation
2
– chemicals / tablets / medicine to kill bacteria /
produced by microbes / eq;
– produced by wbc /
lymphocytes in response to an antigen /
produced by plasma cells / eq;
Antibiotics
Antibodies
[Reject viruses]
[Ignore fight infection]
2
[6]
11.
(a)
(b)
A suggestion to include:
1. some cacti have longer roots / long roots (qualified) / eq;
2. longer rooted cacti take in more water / eq;
3. longer rooted cacti more likely to survive /
survival of the fittest /eq;
4. longer rooted cacti reproduces / eq;
5. longer rooted cacti better adapted to environment /
shorter rooted cacti may die / become extinct / eq;
6. population of cacti changes over time /
evolve (to have longer roots) / eq;
[Allow complete reverse argument for shorter rooted cacti]
[Apply mark scheme to size of cactus]
4
(i)
→
(D)
→
A
C
→
→
B
modern
cat
[Deduct 1 mark for each error]
(ii)
An explanation to include two from:
1. teeth which are least similar are most distant ancestors / eq;
2. teeth become more similar to modern cat / bigger /
stronger (over time) /eq;
3 number of teeth less / shape of teeth changes /eq;
4. shape of jaw changes from flat to rounded over time / eq;
5. similar teeth suggest similar diet to modern cat / eq;
2
[8]
12.
(a)
AA
A
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aa
A
a
;
a
;
2
4
Biology Unit 10: Inheritance
(b)
(i)
Year 11 Higher Level
A
a
A
AA
Aa
Aa
[Deduct 1 mark for each error]
ANSWERS
a
aa
;
;;
3
Candidates’ answers in punnet square form only gain credit.
If both lines and punnet square given the answers on lines take precedence.
(c)
(ii)
3:1 / 3 in 4 yellow to white / 1 in 4 white to yellow;
1
(iii)
150 yellow;
50 white;
[Accept candidates’ ratios from (ii) applied to 200 seeds]
1
An explanation to include three from:
1. breed / “Peaches and Cream” / eq;
2. named good feature of other variety / larger seeds / more seeds /
more yellow / more white / sweeter / eq;
3. collect seeds / seeds produced / eq;
4. grow seeds / eq;
5. test new sweet corn / eq;
6. continue process / repeat / further selective breeding / eq ;
3
plus one communication mark for presenting relevant information that
suits its purpose;
1
[11]
13.
(a)
(b)
four chromosomes present in each;
two larger / two smaller;
[Chromosomes must be single as parent to get both], doubled
ones get 1 mark only]
Any two from:
1. meiosis produces haploid cells / half the chromosome
produces cells with single chromosomes / n;
2. four cells produced by meiosis / double division;
3. gametes / cells from meiosis show variation / ORA;
[Ignore reference to numbers of chromosomes]
2
2
[4]
14.
(a)
D
C
E
five/six correct
four correct
three correct
two correct
one correct
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B
F
-
A
5 marks
4 marks
3 marks
2 marks
1 mark
5
5
Biology Unit 10: Inheritance
(b)
(c)
Year 11 Higher Level
ANSWERS
2 cells /
chromosomes lie singly in the middle / diploid cells produced /
chromosomes in pairs in daughter cells / only one division / daughter cells
have 4 chromosomes / daughter cells identical to parent / eq;
1
mitosis – repair / replacement / growth / making body cells /
produces clones / eq;
[Ignore asexual reproduction]
meiosis – gamete production / sexual reproduction / produces sex cells /
reduction division / produces reproductive cells / production of
haploid cells / eq;
2
[8]
15.
(a)
(i)
(ii)
(b)
make sure results reliable / make more certain of results /
make results more valid / representative / avoid anomalies /
to get a more representative average / to see a pattern /
wider range of outcomes / OWTTE;
[Ignore to get a better average / make results more accurate]
A suggestion to include two from:
1. method / how he did experiment / how he grew plants /
draw apparatus;
2. results / description of results / genetic diagrams;
3. conclusions /what he found out;
4. suggested other experiments / criticisms / evaluated;
5. drawings of his observations / peas / plants / eq;
A suggestion to include two from:
1. fewer offspring idea;
2. ethical objections/ cruelty/
named ethical objection to working with humans animals /
religious objection;
3. animals harder to grow / keep alive / look after /
difficult to mate / harder to manage /
qualified cost e.g. more to feed / house;
4. animals can pass on diseases to humans;
[Ignore reference to unqualified cost/
time to maturity i.e. animals take longer to grow]
1
2
2
[5]
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6
Biology Unit 10: Inheritance
16.
(a)
Year 11 Higher Level
ANSWERS
Nn;
NN;
2
(b)
two;
1
(c)
zero/eq;
1
(d)
half/eq;
1
[5]
17.
(a)
C/Lucy and Daniel have same coloured eyes;
(b)
(i)
(ii)
1
male;
blue;
2
X from ovum/mother;
Y from sperm/father;
2
(c)
bb;
1
(d)
(i)
Lucy;
1
(ii)
Rachel’s twin must:
 be a girl/Lucy or Sarah;
 have brown eyes/can’t have blue eyes;
2
[9]
18.
(a)
(b)
Bb X bb;
BB X bb;
(i)
Bb
X
B b
2
Bb;
B
b;
2
(ii)
3:1/ 31/ 3 to 1 / 3 in 4 / ¾ /75%/0.75/eq;
1
(iii)
12 000;
8 000/4 000;
2
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7
Biology Unit 10: Inheritance
(c)
Year 11 Higher Level
ANSWERS
(i)
An explanation to include six from:
1. more light (than dark) in 1888/more dark (than light) in 1998/ORA;
2. camouflaged/not seen/better adaption/ORA;
3. light surface/unpolluted/little pollution/ORA;
4. not eaten/killed/survive/survival of fittest/selected for/ORA;
5. predators/birds/eq;
6. reproduce/breed/eq;
7. DNA/allele/genes/passed on/eq;
8. (to) offspring/eq;
9. reference to change in environment/background/pollution/eq;
10. mutation/change in DNA/eq;
6
(ii)
mutation/change in DNA/change in genes/eq;
1
[14]
19.
(a)
1
J
(b)
K
An explanation to include two from:
 have the cystic/recessive allele/masked by the dominant allele/eq;
[Reject gene]
 do not have cystic fibrosis/abnormal mucus/have normal mucus/does not
suffer (symptoms)/not affected/can breathe/digest properly/eq;
 can be passed on/eq;
2
(c)
three;
1
(d)
female with cystic fibrosis;
1
(e)
1 in 4 /
1
/ 0.25 / 25% / 1:3 /eq;
4
[Reject 1:4]
1
1
/ 0.125 / 12.5% / 1:7 /eq;
8
[Reject 1:8]
1
(f)
1 in 8 /
[7]
20.
nucleus;
chromosome;
allele;
variation;
environment;
5
[5]
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8
Biology Unit 10: Inheritance
21.
Year 11 Higher Level
ANSWERS
(a)
A
T
C
C
C
G
T
A
G
G
G
C
;;
2
All six correct - 2 marks
five correct - 1 mark
four or less correct - 0 marks
(b)
(double) helix/spiral/twisted ladder;
(c)
(i)
(ii)
(d)
1
gene transfer/genetic modification/genetic
engineering/transgenic/genetic manipulation/(gene) splicing;
1
asexual reproduction/cloning/mitosis/binary fission;
1
insulin/growth hormone/any named human hormone;
1
[6]
22.
(a)
(i)
numbers remain constant/eq;
over a long period of time;
2
A suggestion to include two from:
 predation;
 some survive;
 to continue the species/eq;
2
(iii)
mutation/environmental factor/eq;
1
(iv)
A description to include three from:
 environmental pressure/eq;
 competition;
 individuals with beneficial characteristics;
 survive;
 reproduce;
 pass on characteristic to offspring;
4
(ii)
plus one communication mark for ensuring that spelling, punctuation and grammar
are accurate, so that the meaning is clear;
(b)
nature plays an important part in artificial section;
1
(C)
lecture;
publish (in journal);
2
[12]
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9