Inheritance Question
Booklet
Name………………………………….…..
Target Grade…………………..
Grade achieved……………….
__/94
__%
Unit 4- Woodford County High School
1.
The inheritance of ABO blood groups is controlled by three alleles of the same gene, IA
IB and IO. The alleles IA and IB are codominant. Both IA and IB are dominant to the allele
IO.
(a)
Explain what is meant by an allele.
....................................................................................................................................
....................................................................................................................................
(1)
(b)
(i)
Complete the table to show the missing genotypes.
Blood group
phenotype
Possible
genotype
A
IAIA, ..........
B
IBIB, ..........
AB
......................
O
......................
(2)
(ii)
Children of blood groups A and O were born to parents of blood groups A
and B. Complete the genetic diagram to show the possible ABO blood
group phenotypes of the children which could be produced from these
parents.
Parental phenotypes
Blood group A
Blood group B
Parental genotypes
Genotypes of gametes
Genotypes of children
Phenotypes of children
(3)
(Total 6 mark)
Unit 4- Woodford County High School
2.
The diagram shows the pathway by which phenylalanine is normally metabolised.
phenylalanine
enzyme A
tyrosine
DOPA
melanin
(dark pigment in skin, hair and eyes)
dopamine
(brain transmitter involved in motor coordination)
Phenylketonuria (PKU) is a condition which results from the absence of enzyme A.
People with PKU are homozygous for a recessive allele which fails to produce this
enzyme.
(a)
Use the information shown in the diagram to give one symptom you might expect
to be visible in a person who inherits PKU.
.....................................................................................................................................
(1)
(b)
Explain how gene mutation may result in an allele which fails to produce a
functional enzyme.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Unit 4- Woodford County High School
(c)
(i)
A child with PKU was born to two unaffected parents. Complete the genetic
diagram to show how this is possible.
Parental phenotypes
Parental genotypes
Genotypes of gametes
Genotypes of children
Phenotypes of children
(2)
(ii)
What is the probability that a second child born to these parents will have
PKU?
..........................................................................................................................
(1)
(Total 7 marks)
Unit 4- Woodford County High School
3.
(a)
Explain what is meant by
a recessive allele;
....................................................................................................................................
....................................................................................................................................
a sex-linked gene.
....................................................................................................................................
....................................................................................................................................
(2)
(b)
Nail-patella syndrome is an inherited condition caused by a single gene. Sufferers
have abnormal nail growth and underdeveloped kneecaps. The pedigree shows
how members of one family were affected by the syndrome.
Affected
male
1
2
Unaffected
male
Affected
female
3
5
6
7
4
8
9
Unaffected
female
10
Explain one piece of evidence from the pedigree which indicates that
(i)
the allele for the nail-patella syndrome is dominant;
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(ii)
the gene is not sex-linked.
..........................................................................................................................
..........................................................................................................................
(2)
(Total 6 marks)
Unit 4- Woodford County High School
4.
In a species of fruitfly, females have two X chromosomes, and males have an X and a Y
chromosome.
A gene controlling eye shape in fruitflies is sex-linked, and found only on the X
chromosome.
This gene has two alleles, R for round eyes and B for bar eyes.
A homozygous, round-eyed female (XR XR) was crossed with a bar-eyed male. In the
offspring (Offspring 1), all the female offspring had wide bar eyes (intermediate in size)
and all the males had round eyes.
The figure shows the head of three fruitflies
Wide
bar
eye
(a)
Bar
eye
Round
eye
Name the relationship between the two alleles that control eye shape.
.....................................................................................................................................
(1)
(b)
Give the genotype of the male parent.
.....................................................................................................................................
(1)
Unit 4- Woodford County High School
(c)
Offspring 1 were allowed to interbreed. Complete the genetic diagram to show the
phenotypic ratio you would expect in the resulting Offspring 2.
Parental phenotypes
male
Parental genotypes
Offspring 1 phenotypes
male
Round-eyed female
Bar-eyed
XR XR
Wide bar-eyed female
Round-eyed
Offspring 1 genotypes
Gametes
Offspring 2 genotypes
Offspring 2 phenotypes
and ratio
(3)
(Total 5 marks)
Unit 4- Woodford County High School
5.
(a)
Explain what is meant by
(i)
a recessive allele;
..........................................................................................................................
..........................................................................................................................
(ii)
codominant alleles.
..........................................................................................................................
..........................................................................................................................
(2)
(b)
Chickens homozygous for black feathers were crossed with chickens homozygous
for white feathers. These colours are determined by alleles of a single gene. All the
F1 offspring had blue feathers.
When the blue-feathered F1 chickens were crossed with each other, there were
black-feathered, white-feathered and blue-feathered chickens in the F2 offspring.
(i)
Complete the genetic diagram to explain. how the F1, and F2 phenotypes
were produced.
Parental phenotypes
Parental genotypes
Black-feathered
FBFB
White-feathered
FWFW
F1 genotype
F1, gametes
F2 genotypes
F2 phenotypes
feathered
Black-feathered
White-feathered
Blue(4)
(ii)
The number of black-feathered, white-feathered and blue-feathered chickens
in the F2 offspring was counted. The observed ratio of black : white : blue
was similar to the ratio expected from theory but not the same. Explain why
observed ratios are often not the same as the expected ratios.
..........................................................................................................................
..........................................................................................................................
(2)(Total 8 marks)
Unit 4- Woodford County High School
6.
(a)
Explain what is meant by
(i)
an allele;
..........................................................................................................................
..........................................................................................................................
(ii)
a sex-linked gene.
..........................................................................................................................
..........................................................................................................................
(2)
(b)
Becker muscular dystrophy is an inherited condition caused by an allele of a gene.
Sufferers experience some loss of muscle strength. The diagram shows how
members of one family were affected by the condition.
1
Affected
male
2
Unaffected
male
3
6
7
(i)
4
8
9
Unaffected
female
5
10
11
Explain one piece of evidence from the diagram which shows that the allele
for Becker muscular dystrophy is recessive.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(ii)
The allele for Becker muscular dystrophy is sex-linked. Explain how
individual 9 inherited the condition from his grandfather.
..........................................................................................................................
..........................................................................................................................
...........................................................................................(2)(Total 6 marks)
Unit 4- Woodford County High School
7.
The production of pigment in rabbit fur is controlled by two genes.
One gene controls whether any pigment is made. This gene has three alleles. Allele A
codes for the production of one form of the enzyme tyrosinase, which converts tyrosine
into a black pigment. Allele Ah codes for the production of a second form of the enzyme,
which becomes inactive at temperatures close to a rabbit’s core body temperature, so
only the face, ears, legs and tail are pigmented. A third allele, a, fails to code for a
functional tyrosinase.
The other gene controls the density of pigment in the fur. This gene has two alleles.
Allele B is dominant and results in the production of large amounts of pigment, making
the fur black.
Allele b results in less pigment, so the fur appears brown.
(a)
How do multiple alleles of a gene arise?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
The table shows some genotypes and phenotypes.
Genotype
Phenotype
A–B–
all fur black
aaB–
all fur white (albino)
ahabb
white body fur with brown face, ears, legs and tail (Himalayan)
(i)
What do the dashes represent in the genotype of the black rabbit?
..........................................................................................................................
..........................................................................................................................
(1)
(ii)
Give all the possible genotypes for a Himalayan rabbit with black face, ears,
legs and tail.
..........................................................................................................................
(2)
(iii)
Suggest an explanation for the pigment being present only in the tail, ears,
face and legs of a Himalayan rabbit.
..........................................................................................................................
..........................................................................................................................
(2)
Unit 4- Woodford County High School
(c)
Using the information given, explain why the phenotypes of rabbits with AABB
and AahBB genotypes are the same.
.....................................................................................................................................
(2)
(Total 9 marks)
8.S
A woman comes from a family with a history of the sex-linked condition haemophilia. A
test was carried out to discover the sex of one of the embryos produced by IVF.
(i)
Explain how observation of the chromosomes from an embryo cell could enable
the sex to be determined.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(ii)
The mother is known to carry the haemophilia allele. The father does not have
haemophilia. What is the probability of their first child having haemophilia?
Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 5 marks)
9.
In a breed of cattle the H allele for the hornless condition is dominant to the h allele for
the horned condition. In the same breed of cattle the two alleles CR (red) and CW (white)
control coat colour. When red cattle were crossed with white cattle all the offspring were
roan. Roan cattle have a mixture of red and white hairs.
(a)
Explain what is meant by a dominant allele.
.....................................................................................................................................
.....................................................................................................................................
(1)
(b)
Name the relationship between the two alleles that control coat colour.
.....................................................................................................................................
(1)
Unit 4- Woodford County High School
(c)
Horned, roan cattle were crossed with white cattle heterozygous for the hornless
condition. Compete the genetic diagram to show the ratio of offspring phenotypes
you would expect.
Parental phenotypes
Horned, roan
×
hornless, white
Parental genotypes
Gametes
Offspring genotypes
Offspring phenotypes
Ratio of offspring
phenotypes
(4)
(d)
The semen of prize dairy bulls may be collected for in vitro fertilisation. The
sperms in the semen can be separated so that all the calves produced are of the
same sex. The two kinds of sperms differ by about 3% in DNA content.
(i)
Explain what causes the sperms of one kind to have 3% more DNA than
sperms of the other kind.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(ii)
Suggest one reason why farmers would want the calves to be all of the same
sex.
..........................................................................................................................
..........................................................................................................................
(1)
(Total 9 marks)
Unit 4- Woodford County High School
10.
In cats, one of the genes for coat colour is present only on the X chromosome. This gene
has two alleles. The allele for ginger fur, XB, is dominant to that for black fur, Xb
(a)
All the cells in the body of a female mammal carry two X chromosomes. During
an early stage of development one of these becomes inactive and is not expressed.
Therefore female mammals have patches of cells with one X chromosome
expressed and patches of cells with the other X chromosome expressed.
Tortoiseshell cats have coats with patches of ginger and patches of black fur.
(i)
What is the genotype of a tortoiseshell cat?
..........................................................................................................................
(1)
(ii)
Explain why there are no male tortoiseshell cats.
..........................................................................................................................
(1)
(b)
A cat breeder who wished to produce tortoiseshell cats crossed a black female cat
with a ginger male. Complete the genetic diagram and predict the percentage of
tortoiseshell kittens expected from this cross.
Parental phenotypes:
black female
Parental genotypes:
.........................
........................
Gamete genotypes:
.........................
........................
ginger male
Offspring genotypes: ..................................................................................................
Percentage of tortoiseshell kittens:
.............................................................................
(3)
(Total 5 marks)
Unit 4- Woodford County High School
11.
In the flour beetle, the allele for red body colour (R) is dominant to the allele for black
body colour (r). A mixed culture of red beetles and black beetles was kept in a container
in the laboratory under optimal breeding conditions. After one year, there were 149 red
beetles and 84 black beetles in the container.
(a)
Use the Hardy-Weinberg equation to calculate the expected percentage of
heterozygous red beetles in this population.
Answer: ..............................................
(3)
(b)
Several assumptions are made when using the Hardy-Weinberg equation. Give
two of these.
1..................................................................................................................................
2..................................................................................................................................
(2)
(Total 5 marks)
12.
The diagram shows three generations of a family.
1
2
5
6
3
4
7
8
9
10
11
Key:
Unaffected male
Unaffected female
Affected male
Affected female
No member of the family showed the symptoms of cystic fibrosis (CF) until the son was
born in the third generation. A single gene is responsible for the inheritance of cystic
fibrosis.
Unit 4- Woodford County High School
(a)
Assume that no gene mutations have occurred in these generations. Use F for the
dominant allele and f for the recessive allele to give the possible genotype or
genotypes of:
individual
7;.................................................................................................................
individual
11................................................................................................................
(2)
(b)
Give the probability that the next child of parents 7 and 8 will be a girl with cystic
fibrosis.
Show how you arrived at your answer.
Probability that child will be a girl with cystic fibrosis: ............................................
(2)
(c)
In the UK, 1 in every 2 500 children has cystic fibrosis. What is the frequency of
the cystic fibrosis allele in children in the UK? Show how you arrived at your
answer.
Frequency of cystic fibrosis allele: ...........................
(2) (Total 8 marks)
Unit 4- Woodford County High School
13.
In cats, some aspects of the inheritance of fur colour are sex linked. When a ginger male
cat was crossed with a black female, all the female kittens were tortoiseshell (a pattern of
black hairs and ginger hairs) and all the male kittens were black. However, in the
reciprocal cross, although all the female kittens were again tortoiseshell, the male kittens
were ginger.
(a)
Complete the following genetic diagrams to explain the results of these two
crosses.
Use the following symbols:
XB = an X-chromosome carrying an allele for black hair.
XG = an X-chromosome carrying an allele for ginger hair.
Cross 1
Cross 2
Parental phenotypes
Ginger x Black
male
female
Black
male
x Ginger
female
Parental genotypes
..........
..........
..........
..........
Gametes
................... ...................
................... ...................
Offspring genotypes
........................................
........................................
Offspring phenotypes
.......................................
.......................................
.......................................
.......................................
(4)
(b)
Why were no male tortoiseshell cats produced in these crosses?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 5 marks)
Unit 4- Woodford County High School
14.
Huntington’s disease is a human inherited condition resulting in gradual degeneration of
nerve cells in the brain. It is caused by a dominant allele but usually no symptoms are
evident until the person is at least 30 years old. It is very rare in most populations.
However, in one isolated area in Venezuela, 48% of the population possess a genotype
which gives rise to Huntington’s disease. Many of the inhabitants of this area can trace
their origins back to a common ancestor 200 years ago.
(a)
Use the Hardy-Weinberg equation to estimate the percentage of this Venezuelan
population which is heterozygous for Huntington’s disease. Show your working.
Answer = ....................................... %
(3)
(b)
Suggest why
(i)
there is such a high incidence of Huntington’s disease in this population;
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(ii)
Huntington’s disease has not been eliminated from this population by
natural selection.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(3)
(Total 6 marks)
Unit 4- Woodford County High School
15.
Red-green colour blindness is caused by a mutation in the gene coding for one of the
opsin proteins which are needed for colour vision. The diagram shows the inheritance of
red-green colour blindness in one family.
1
5
2
6
3
7
10
8
11
4
9
12
14
13
15
16
Key
= colour-blind male
= unaffected male
= unaffected female
Person 12 is pregnant with her fourth child. What is the probability that this child will be
a male with red-green colour blindness? Explain your answer by drawing a genetic
diagram. Use the following symbols
XR = an X chromosome carrying an allele for normal colour vision
Xr= an X chromosome carrying an allele for red-green colour blindness
Y = a Y chromosome
Probability = ......................................
(Total 4 marks)
Unit 4- Woodford County High School
Mark Scheme
1.
(a)
(different) forms of a gene;
(b)
(i)
(ii)
1
IAIO; IBIO; IAIB; IOIO;
(4 correct = 2 marks; 3 or 2 correct = 1 mark; 1 correct = 0)
IAIO
genotypes
IBIO
max 2
1
gametes
IA
IO
IB
IO
1
genotypes
phenotypes
IAIB
AB
IAIO
A
IBIO
B
IOIO
O;
1
[6]
2.
(a)
lack of skin / eye / hair pigment/ fair skin/ hair/poor co-ordination;
1
(b)
alteration in sequence / deletion / substitution / addition of nucleotides/bases;
incorrect amino acids inserted into polypeptide / protein;
alters active site / substrate cannot bind;
3
(c)
(i)
(ii)
Parental pheno types
Parental genotypes
Genotypes of gametes
normal
Nn
N+n
Genotypes of children
Phenotypes of children
NN Nn
Normal Normal
x
x
x
normal
Nn
N+n;
1
Nn
nn
Normal Affected;
1
25% / ¼ / 0.25 / 1 in 4;
1
[7]
3.
(a)
(b)
recessive only expressed (in the phenotype) when
homozygous
1
sex-linked gene is on the X chromosome (in humans)/
Y chromosome.
1
(i)
(ii)
3 and 4 produce unaffected male/8 / female/10, so must
carry recessive;
but both affected by nail-patella which must be dominant.
3 inherits X from mother, who is not affected;
Unit 4- Woodford County High School
2
if sex-linked, 3 would have nail-patella on X chr and
would pass on to all female offspring;
10 is recessive female, so gene not sex-linked.
max 2
[6]
4.
(a)
Condominance;
(Allow incomplete / inheritance without dominance)
1
(b)
XBY OR B(-);
1
(c)
Parental genotypes are given:
XR XR
(XB Y) - no mark
Offspring 1 genotypes:
XR XB
XR Y
XR XB
X RY
XR XR
Offspring 2 genotypes:
Offspring 2 phenotypes: round eyed
female
Ratio:
1
;
XB Y
;
wide-bar round eye bar-eye
female
male
male;
:
1
:
1
:
3
1
(Ignore ratio unless it contradicts: be alive to other possible ratios)
(No marks as such for “gametes”, though may inform markers where unclear.)
[5]
5.
(a)
(b)
recessive,
only expressed in phenotype if homozygous;
codominant alleles,
both expressed (in phenotype), if both present,
(i)
(ii)
2
F1, - FB FW;
gametes clearly indicated – FB and FW;
F2 genotypes correct and in correct order –
FBFB FWFW FBFW
working clearly set out;
4
chance related to mating;
random fusion of gametes;
small sample size;
differential mortality;
2 max
Unit 4- Woodford County High School
6.
(a)
allele,
one form of a (specific) gene;
sex-linked,
on sex chromosomes/X/Y;
b)
(i)
3 and 4 do not show the condition but 9/one male does;
4 must be carrier;
OR
1 affected but not daughter/4;
who gets X from father;
(ii)
grandfather/1 passed on his (affected) X chromosome
to his daughter/4;
who was unaffected, because of the ‘normal’ X
inherited from her mother/2;
9 inherited his X chromosome from his mother/4;
1
1
2
2 max
[6]
7.
(a)
(b)
(c)
mutations;
which are different/at different positions in the gene;
2
(i)
either dominant or recessive allele;
1
(ii)
ahah BB, ahaBB, ahah Bb, ahaBb;;
(allow 1 mark for 2 or 3 correct answers)
2
(iii)
temperature lower at extremities;
enzyme active/ not denatured;
if allele A is present (normal) tyrosinase/enzyme is produced, so it does
not matter what other allele is present / explanation of why heterozygote is
same phenotype as double dominant in terms of enzyme produced;
phenotype/rabbit is black as both have alleles A and B;
2
2
[9]
(i)
female XX, male XY;
Y shorter/smaller than X;
(ii)
haemophilia is a recessive allele;
defective allele (gene) present on X, missing from Y;
male 0.5(50%/½) probability of haemophilia;
female 0/no chance;
(0.25(25%/¼) first baby having haemophilia);
or
Unit 4- Woodford County High School
2
XHXhXHY;
XHXH + XHXh + XHY + Xh Y;
XhY is a sufferer
3 max
[5]
9.
(a)
is always expressed(in the phenotype) / produces (functional) proteins;
1
(b)
codominance;
1
(c)
Parental geneotypes -
hhCRCw,
hCR
HhCwCw;
hCW
HCW
hCW
GametesOffspring geneotypes - HhCRCw, hhCRCw, HhCwCw, hhCwCw;
Offspring pheneotypes - hornless horned hornless horned
roan
1
Ratio of offspring -
(d)
(i)
(ii)
roan
1
white
1
white
1;
4
sperm(with more DNA) have X chromosome;
X is larger / has more genes than Y;
2
female for milk / males for meat / male or female for breeding;
1
[9]
10.
(a)
(b)
(i)
XBXb /XBXb
(ii)
Need two X chromosomes / males have only one X /
male has a Y / X and Y chromosome / no allele on Y;
Parental genotypes
gamete genotypes
offspring genotypes
1
XbXb
Xb
1
XBY
XB
Y;
XX
X Y / correct from
given gametes
if sex-linked;
percentage of tortoiseshell kittens = 50% / correct from offspring genotype
given;
b B
b
3
[5]
11.
(a)
EITHER:
q2 = 0.36 / q = 0.6/0.61;
p = (1 – 0.6) = 0.4/0.39;
48/47.9 = 3 marks
OR (If no correct calculations)
Unit 4- Woodford County High School
(b)
Allow 1 mark for use of H – W equation:
p + q = 1 /p2+2pq + q2 = 1
max. 3
No selection;
random mating/no sexual selection;
large population/gene pool;
no emigration/immigration/no migration/isolated population;
no mutation;
equally viable gametes/all equally fertile;
generations do not overlap;
max. 2
[5]
12.
(a)
1ndividual 7 Ff,
individual 11 FF and Ff,
(b)
Working shows probability next child will have cystic fibrosis =
and M/F = 50% / 0.5/½;
1
answer given as
/ 0.125 / 1 (chance) in 8 / 12.5%;
8
(c)
(d)
1
1
1
4
or 0.25
2
(i)
Able to insert nucleic acid/DNA into cells/viruses enter/invade cells;
1
(ii)
Difficult to get DNA/modified gene (or equivalent) into sufficient
cells/DNA may be inserted but not expressed;
correct reference to use of method on somatic/body cells not at
gamete/zygote stage;
DNA only inserted into differentiated cells;
treatment must be repeated;
correct reference to effects of cystic fibrosis on other organs;
max. 1
Calculation attempts to find square root of 2 500 or 1/2500 or 0.0004;
0.02;
A 1/50 or 1 in 50 or 2%
2
[8]
13.
(a)
Parental genotypes and gametes correct:
XGY XBXB
XBY XGXG
;
XG
;
Y
XB
XB Y
XG
Offspring genotypes and phenotypes correct:
XBXG
X BY
XBXG
XGY
ONLY these. BUT if error, then award phenotypes if
Unit 4- Woodford County High School
;
correct re. candidate’s genotypes
tortoiseshell
black
tortoiseshell
female
male
female
Must relate to stated genotypes
(b)
ginger
male ;
Male has Y with no gene / allele for colour / must have both
B and G to be tortoiseshell / male cannot have B and G /
2 colour alleles / male can only have B or G / only 1 colour
allele;
4
1
[5]
14.
(a)
(q2 = 0.52 / q = 0.72)
(p = 1 – 0.72 = 0.28)
p + q = 1 / p2 + 2pq + q2 = 1 ;
Answer = 2pq / use of appropriate numbers;
Answer = 40%;
(b)
3
Any three from: (MARK AS A WHOLE)
Small founder population / common ancestor;
Genetic isolation / small gene pool / no immigration /
no migration / in-breeding;
High probability of mating with person having H-allele;
Reproduction occurs before symptoms of disease are apparent;
Genetic argument – Hh x hh  50% / Hh x Hh  75% affected
offspring;
No survival / selective disadvantage;
Ignore ‘survival of the fittest’
3 max
[6]
15.
parental genotypes correct: XRXr AND XRY;
gametes correct for candidate’s parental genotypes;
offspring genotypes correct and colourblind male identified as XrY /
correct genotypes derived from cand’s gametes and identify XrY;
correct probability = ¼ / 0.25 / 25% / 1 in 4 / 1:3 ;
4
[4]
Unit 4- Woodford County High School