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INTERACTIVE
MULTIPLE CHOICE
QUESTIONS
Genetics
The answers are provided.
Explanations of why the alternatives
are unsatisfactory are also offered
These multiple choice questions are similar to the ones
set by the GCSE and IGCSE Examination Boards
except that, in some cases, there may be more than one
acceptable answer
For this reason, even if you select a correct answer at
your first attempt, it is worth looking at all the
alternatives
(a) to see if there is a better answer and
(b) to see why some of the alternatives are
unacceptable
Question 1
A father’s blood group is AB; the mother’s is O.
Which of the following blood groups could appear in their
offspring?
(a) A
(b) B
(c) AB
(d) O
Question 2
Yes
The father’s genome must be iAiB
The mother’s genome will be iOiO
The combination iAiO is possible and will be expressed
as group A because iA is the dominant allele
Yes
The father’s genome must be iAiB
The mother’s genome will be iOiO
The combination iBiO is possible and
will be expressed as group B
because iB is the dominant allele
No
The father’s genome must be iAiB
The mother’s genome will be iOiO
The offspring will all inherit either iA or iB from their
father and iO from their mother. Their genomes will be
either iAiO (expressed as group A) or iBiO (expressed as
Group B. Group AB is not possible
No
The father’s genome must be iAiB
The mother’s genome will be iOiO
The offspring will all inherit either iA or iB from
their father and iO from their mother. Their
genomes will be either iAiO or iBiO. The alleles
iA and iB are both dominant to iO so group O is
not possible
Question 2
A pure-breeding male black mouse is mated with a female brown
mouse and they produce a litter of 12. The allele for black fur is
dominant to the allele to brown fur.
What is the expected distribution of colour and sex in their litter?
(a) 6 brown females and 6 black males
(b) 9 black and 3 brown, all male
(c) 6 black males and 6 black females
(d) 12 black males
Question 3
No
The pure-breeding male’s genome must be BB and the brown
mouse’s genome must be bb. The allele for black fur is
dominant over the brown allele. Therefore all the offspring
will be black (Bb)
gametes
Black
male
Brown
female
B
B
b
Bb
Bb
b
bB
bB
No
As explained in the previous slide, the allele for black fur is
dominant to the brown allele, so there can be no brown mice
in the litter from this cross
gametes
Black
male
Brown
female
B
B
b
Bb
Bb
b
bB
bB
Yes
Inheritance of colour is explained in the first answer. The male
mouse carries the X and Y chromosomes. The female mouse
carries two X chromosomes. At meiosis, only one of each
chromosome pair goes to the gametes.
gametes
Black
male
Brown
female
BX
BY
bX
BbXX BbXY
bX
bBXX bBXY
No
Certainly all 12 mice will be black as explained in the first
answer, but the sex is inherited as explained in the third answer, so
the expectation is that there will be 6 males and 6 females in the
litter
Question 3
A male heterozygous black mouse (Bb) is mated with a female
heterozygous black mouse (Bb) and the litter consists of 12
pups. B is the allele for the black colour. The allele for brown
colour is b. The dominant allele is B.
Which of
these ratios is closest to the expected ratio for the distribution
of colour among the offspring?
(a) All black
(b) 6 black and 6 brown
(c) 4 black and eight brown
(d) 8 black and 4 brown
Question 4
X
Not very close
From the Punned square you can see that the expected
ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes
B
b
B
BB
Bb
b
Bb
bb
These are only the chance combinations. It would be
possible to produce 12 black pups, since ‘black’ is the
dominant allele but this is not close to the expected ratio
Not very close
From the Punnett square you can see that the expected
ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes
B
b
B
BB
Bb
b
Bb
bb
These are only the chance combinations. It would be
possible to produce 6 black and 6 brown pups but this
is not very close to the expected ratio of 9:3
Close but …
From the Punnett square you can see that the
expected ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes
B
b
B
BB
Bb
b
Bb
bb
These are only the chance combinations.
A
combination of 4 black to 8 brown is close to the expected
ratio of 3:9 but since black is the dominant allele it seems to
be the wrong way round
The closest
From the Punnett square you can see that the expected
ratio is 3 black (BB or Bb) to 1 brown (bb)
gametes
B
b
B
BB
Bb
b
Bb
bb
These are only the chance combinations.
A
combination of 8 black to 4 brown is closest to the expected
ratio of 9:3
Question 4
The diagrams represent stages in cell
division by mitosis. (only one
chromosome is represented). What is
the correct sequence of events?
(a) a b c d e
a
d
(b) b a c e d
(c) b a d c e
b
(d) d b a c e
e
c
Question 5
No
The chromosomes shorten and thicken (b) after they
have appeared in the nucleus (b). Similarly at the end
of cell division, the chromosomes extend and become
less visible (d) after the cell divides (e)
Yes
This is the correct sequence
No
The cell does not start to divide (d) until the chromatids
have separated (c). Also, cell constriction (e) precedes
cell division (d)
No
Cell division (d) does not take place until the chromatids
have appeared (b) and separated (c). Also, cell
constriction (e) precedes cell division (d)
Question 5
The process of cell division by meiosis takes place only…
(a) in skin cells
(b) in red bone marrow
(c) in reproductive organs
(d) in lymphocytes
Question 6
No
Although the cells in the basal layer of skin divide rapidly, it is
by mitosis
No
Cells in the red bone marrow divide rapidly to produce
red and white blood cells, but this is by mitosis
Yes
The cells in the reproductive organs which produce
gametes will undergo a meiotic division and produce
haploid gametes
No
The lymphocytes are capable of dividing rapidly to
produce clones of cells but this involves only mitosis
Question 6
In a DNA molecule, which of the molecules listed
below pairs with adenine?
(a) thymine
(b) guanine
(c) valine
(d) cytosine
Question 7
Yes
adenine
thymine
No
Guanine pairs with cytosine
guanine
cytosine
No
Valine is an amino acid and not an organic base
No
Cytosine pairs with guanine
cytosine
guanine
Question 7
If L is the allele for long hair and l is the allele for short hair,
B is the allele for black hair and b is the allele for white hair,
S is the allele for straight hair and s is the allele for curly hair
What will be the phenotype for a small dog with the
genotype LLBbss?
(a) Long, white, straight fur
(b) Short, black, straight fur
(c) Long, white, curly fur
(d) Long, black, curly fur
Question 8
No
The allele for black fur is dominant to the allele for
white fur
No
The dog carries both dominant alleles for long hair
No
The dog is heterozygous for the colour gene, but the allele
for black fur is dominant to the allele for white fur
Yes
The dog is homozygous recessive for the curly allele,
homozygous dominant for hair length and heterozygous for the
colour gene but the black allele is dominant
Question 8
Bacteria can be genetically modified to produce human
insulin. The steps involve …
(a) cutting out the insulin gene from human
DNA with restriction enzymes,
(b) extracting plasmids from the bacterium,
(c) returning the modified plasmid to the bacterium,
(d) inserting the insulin gene into the plasmid,
(e) cutting open the plasmid with the same restriction enzyme
Which of the following is the correct sequence?
(1) e, b, d, a, c
(3) b, e, a, d, c
(2) b, c, e, a, d
(4) b, d, e, a, c
Question 9
No
The plasmids cannot be cut open (e) until they are
extracted from the bacterium (b)
No
The insulin gene must be inserted in the plasmid (d)
before it is returned to the bacterium (c)
Yes
This is the correct sequence
b, a, e, d, c would also be acceptable because the
restriction enzyme can cut the plasmid DNA and human
DNA in any order
No
The plasmid DNA must be opened (e) before the insulin
gene can be inserted (d)
Question 9
Before natural selection can take place in an animal,
there has to be either …
(a) a gene mutation or
(b) a change of habitat or
(c) a gene recombination or
(d) a climate change
Question 10
Yes
A gene mutation which caused a change in the organism could
be subject to natural selection
No
A change of habitat might favour a variation resulting
from a genetic change, such as a mutation, but selection
could not result from an organism simply changing its
habitat
Yes
A new combination of genes could produce a variation that
had a selective advantage
No
A climate change might favour some variants in a
population but could not, itself, produce those variants.
There has to be a genetic change for the climate change to
act upon
Question 10
Which of the following can be inherited?
(a) Cystic fibrosis
(b) AIDS
(c) Sickle cell disease
(d) Tuberculosis
Yes
Cystic fibrosis is caused by a gene mutation. The gene
controls the movement of salts and water into and out of the
cells. The mutated form of the gene causes thick mucus to be
secreted by the lungs, airways and pancreas, plus many other
symptoms.
The
mutated gene is recessive to the normal gene..
No
AIDS is caused by a virus, the human immunodeficiency
virus (HIV). The virus is transmitted by sexual intercourse
or by infected syringe needles.
An infected mother may pass the disease on to her baby, so
the disease may, superficially, appear to be inherited
Yes
Sickle cell anaemia is caused by a mutation in a gene
controlling the composition of haemoglobin. This mutation
causes the red cells to become distorted in low oxygen
concentrations and so block small blood vessels.
The mutated gene is recessive to the normal gene
No
Tuberculosis is an infectious disease caused by a
bacterium Mycobacterium tuberculosis. The bacteria are
carried in the air.
In most cases, the disease affects the lungs.
End of questions
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