Q1.
In humans, sex chromosomes control whether a person is male or female.
(a)
Use letters X and Y to complete the Punnett square for sex inheritance.
Eggs
or
Sperm
...........XX..........
............................
............................
............................
or
(3)
(b)
A couple already have three boys.
What is the probability that their next child will be a girl?
........................................................................................................................
........................................................................................................................
(1)
(Total 4 marks)
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Q2.
The diagrams show one of Mendel’s experiments.
He bred pea plants.
Mendel suggested that flower colour was controlled by inherited factors.
Draw a ring around the correct answer to complete the following sentences.
dominant.
(a)
The first generation plants show that the red factor is
environmental.
recessive.
(1)
dominant.
(b)
The second generation plants show that the white factor is
environmental.
recessive.
(1)
(c)
What do we call inherited factors?
........................................................................................................................
(1)
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(d)
How are inherited factors passed from generation to generation?
........................................................................................................................
(1)
(Total 4 marks)
Q3.
The diagram shows how cells from human embryos can be used to grow ‘replacement body
parts’ for humans.
(a)
Complete the sentence.
The fertilised egg divides to form the 5-day-old embryo by a process
called ............................................................ .
(1)
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(b)
Some statements about stem cells are given below.
Tick ( ) two advantages and two disadvantages of using stem cells to grow ‘replacement
body parts’ for humans.
Advantage
Tick ( )
Disadvantage
Tick ( )
Stem cells can grow into many different kinds
of body cells.
Stem cells may grow out of control.
Large numbers of stem cells can be grown in
the laboratory.
Stem cells may be used to treat some human
diseases.
Collecting and growing stem cells is
expensive.
Patients treated with stem cells may need to
take drugs for the rest of their life to prevent
rejection.
(4)
(Total 5 marks)
Q4.
The chromosomes for determining the gender or sex of a person are labelled X and Y.
(a)
Complete the Punnett Square to show the genotype of parent 2 and of the four offspring.
(3)
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(b)
Which parent is the mother?
.....................................................................................................................................
(1)
(c)
What are the chances of getting a baby boy?
.....................................................................................................................................
(1)
(Total 5 marks)
Q5.
Cystic fibrosis is an inherited disorder that can seriously affect health.
(a)
Which one of these is affected by cystic fibrosis?
Draw a ring around your answer.
blood
cell membranes
kidneys
nervous system
(1)
(b)
The diagram shows the inheritance of cystic fibrosis in a family. The allele that produces
cystic fibrosis is recessive.
(i)
Explain why Alice inherited cystic fibrosis.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
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(ii)
Explain why Ted did not inherit cystic fibrosis.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(c)
Bob and Carol know that there is a risk that their next baby will have cystic fibrosis.
Embryos can be screened for the allele that produces cystic fibrosis.
Many people support the screening of embryos, but others do not.
(i)
Suggest one reason why many people support the screening of embryos for the
cystic fibrosis allele.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(1)
(ii)
Suggest one reason why many people are against the screening of embryos for the
cystic fibrosis allele.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(1)
(Total 7 marks)
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M1.
(a)
(X)
(XX)
XX
Y
XY
XY
1 mark for Y in sperm box
1 mark if XX box correct
1 mark if both XY boxes correct
3
(b)
1 : 1 or 50% or ½ or 0.5 or 1 in 2 or 1 out of 2 or 50 : 50
do not accept 50/50
accept equal (probability)
1
[4]
M2.
(a)
dominant
1
(b)
recessive
1
(c)
genes
1
(d)
gametes
1
[4]
M3.
(a)
mitosis
1
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(b)
Adv.
Disadv.
Stem cells can grow into many
different kinds of body cells.
Stem cells may grow out of control.
Large numbers of stem cells can
be grown in the laboratory.
Stem cells may be used to treat
some human diseases.
Collecting and growing stem cells
is expensive.
Patients treated with stem cells
need to take drugs for the rest of
their life to prevent rejection.
1 mark for each correctly ticked advantage up to a maximum of
2 marks
1 mark for each correctly ticked disadvantage up to a maximum of
2 marks
deduct 1 mark each for every incorrect box ticked in each column
up to a maximum of 2 deductions in each column
4
[5]
M4.
(a)
clearly labelled ‘y’
1
mark the offspring in two horizontal
rows
1 mark for each fully correct row
allow transferred error if parent 2 is incorrect
XX XX
1
XY
XY
accept YX
1
(b)
parent 1
accept XX
1
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(c)
50:50
or
equal or even
or
1:1 or 50%
accept 1/2 or 2/4
1
[5]
M5.
(a)
cell membranes
1
(b)
(i)
two recessive / cystic fibrosis / faulty / diseased / the allele(s) / genes
two can be implied by second marking point
ignore chromosomes
1
from Bob and Carol / both parents / the parents
if no other marks awarded ‘Carol is a carrier’ gains 1 mark
1
(ii)
(inherited) dominant / normal allele / gene
1
from Carol / mother
ignore references to recessive allele / gene from father / Bob
if no other marks awarded he has just / only one recessive allele
gains 1 mark
1
(c)
(i)
reduce number of people with cystic fibrosis (in population)
or
reduce health-care costs
or
expensive to have baby with cystic fibrosis
accept to allow decision / emotional argument qualified
eg allows abortion
or
allows people to make choices about termination
or
help to prepare financially / emotionally etc
1
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(ii)
any one from:
•
possible damage / risk to embryo / fetus / baby
allow possible harm / risk to mother
•
screening / it is expensive
•
(may) have to make ethical / moral / religious decisions
ignore not natural / playing God / unethical / immoral / religious
unqualified
•
right to life
1
[7]
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