Heredity, Inheritance and Evolution Revision Structured Questions

1. Li-Fraumeni syndrome is a rare inherited condition. lt makes someone much more likely to develop cancer at an early age. Li-Fraumeni syndrome is caused by the dominant allele of a gene (F).
Fig 1.1 shows the family history of a family affected by Li-Fraumeni syndrome. Parents A and B have 2 children, G and D.

st gabriels Q7.PNG

Figure 1.1

(a) Explain the terms gene and allele.

(b) Using info from Fig 1 .1, write down the genotype for the following people:
Person G:
Person A:
Person B:

(c) Persons A and B have a third child, Person E.
Using a genetic diagram, deduce the probability that person E does not have Li-Fraumeni syndrome.

What is the probability that person E does not have Li-Fraumeni syndrome?

It was recently discovered that a mutation in the gene coding for a particular protein is responsible for development of the Li-Fraumeni syndrome.
Apart from gene mutation, mutations may cause a change in the chromosome number.

Fig. 1.2 shows the chromosomes of an individual affected by Down’s syndrome.

st gabriels Q7 B.PNG

Figure 1.2 

(d) With reference to Fig. 1.2, how can we tell that the individual’s suffering from Down’s syndrome?

(e) What is the sex of the individual? Explain your answer.

2. Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan syndrome tend to be unusually tall, with long limbs and long, thin fingers.

Fig. 1.2 shows a family tree.

serangoon Q5.PNG

Figure 2.1

(a) Marfan syndrome is caused by a dominant allele. Jane and John have two children, Adam and Amy. Adam has Marfan syndrome but Amy does not. Use a genetic diagram to explain the difference. lndicate on the diagram who may be Adam and who may be Amy.

(b) Adam marries May who does not have Marfan syndrome. They have two children, Sandy and Danny. Danny does not have Marfan syndrome. What is the
chance of Sandy having Marfan syndrome? You may use the genetic diagram in Fig 2.2 or draw your genetic diagram.

Use M to represent the dominant allele and m to represent the recessive allele.serangoon Q5 B.PNGFigure 2.2

(c) A couple has ten children. Eight of these are boys and two are girls.

(i) Describe how the sex of each child is determined.

(ii)  Suggest why the numbers of boys and girls in this family are not equal. Use these ideas about the chance of a baby being a boy or girr in your answer.



1. (a) Gene is a small segment of DNA that contains information to make a protein OR a small segment of DNA where a specific genetic information is stored. Alleles are alternative/different forms of a gene.

(b) C: ff, A: Ff, B: Ff

(c) IMG20170827135825.jpg

(d) There are three copies of chromosome 21 OR an extra chromosome 21.

(e) The individual is a male. The chromosome for male is XY. The last pair/23rd pair is the sex chromosome and the chromosomes are different in size.




(c)(i) The sex is determined by sex chromosome. If the child has XX, she is a female, else if the child has XY, he is a male.

(ii) The expected ratio of boy or girl is 0.5 or 50%. The expected ratios only indicate the probability/chance of producing the genotypes/phenotypes in offspring. Fertilisation of the sperms with ova is a random event. with small number of offspring, the observed ratios often differ from expected ratios.


Heredity, Inheritance and Evolution Revision MCQ Questions


1. The figure below represents a pair of homologous chromosomes showing four sites where genes are located.

pasir ris crest Q16.PNG

Which numbered parts 1, 2, 3 and 4 are alleles?

A.    1 and 2
B.    3 and 4
C.    1 and 3
D.    1 and 4

2. Which of the following traits in humans is an example of continuous variation?

A.    eye colour
B.    height
C.    blood group
D.    ability to roll the tongue

Refer to the graph below to answer questions 4 and 5. the graph shows the height of a class of students. junyuan Q16.PNG

3. Which of the following can be deduced from the information shown in the graph?

A.    Height can be increased by doing more exercise.
B.    Height is not brought about by the combined effect of many genes.
C.    The mean height is 150 -159 cm.
D.   The height of this class shows discontinuous variation.

4. If the students in the 120-129 cm and 210—219 cm are of the same age and have the same degree of physical exercise and nutrition, what can be the main reason for their differences in height?

A.    genetic drift
B.    genetic variation
C.    mutation
D.    natural selection

5. The shape of a person’s earlobes is determined by a single gene. This gene has dominant and recessive alleles.

The allele for detached earlobes is dominant to the allele for attached earlobes.

The diagram shows the inheritance of earlobe shape in a family.

CHIJ katong Q38.PNG

What is the probability of the next child from the same parents having detached earlobes?

A.    0%
B.    25%
C.    50%
D.    75%

6. The diagram below shows the inheritance of fast twitch muscles (which are useful for sprinting) and slow twitch muscles (which are useful for long distance running) in three generations of horses.

seng kang Q37.PNG

What are the likely gene types of individuals 2, 4 and 8?seng kang Q37 B.PNG

7. In fruit flies, the allele for grey body, G, is dominant over the allele for black body, g. The result of a mating between two flies is shown.

st joseph q35.PNG

What are the genotypes of the parents?

A.    Gg x gg
B.    Gg x Gg
C.    GG x gg
D.    GG x Gg

8. The diagram below shows the inheritance of a recessive characteristic that is controlled by a single pair of alleles T and t.

yuying Q19.PNG

T represents the dominant allele and t represents the recessive allele.

What are the most likely genotypes of individuals P and Q?yuying Q19 B.PNG




Molecular Genetics Revision Structured Questions

1. The diagram below shows part of a DNA molecule.yuying Q6.PNG

(a) Identify the following labelled components: W, X, Y and Z.

(b) DNA molecules are double-stranded molecules held in a specific direction.

(i) Identify the bonds that exist between each DNA strand.

(ii) State the process by which the bonds stated in b(i) are formed.

(iii) Briefly explain how the process stated in b(ii) leads to specificity in proteins.



1. (a) W: Phosphate group, X: Deoxyribose, Y: Cytosine, Z: Adenine

(b) (i) Hydrogen bonds

(ii) Complementary base pairing

(iii) Specific nucleotide sequence is transcribed to a mRNA which is translated to give a polypeptide with specific amino acid sequence determined by the mRNA sequence.

Molecular Genetics Revision MCQ Questions

1.    The diagram below shows part of a DNA molecule.kuo chuan Q38 A.PNG

Which letters indicate cytosine, deoxyribose, phosphate and thymine?

kuo chuan Q38 B.PNG


2.    Which of the following lists (A, B, C or D) has its items organised from largest to smallest by size?
Largest ————————————————-> Smallest
A.    nucleotide, nucleus, base, chromosome, cell, gene
B.    cell, nucleus, chromosome, gene, base, nucleotide
C.    chromosome, nucleus, gene, cell, nucleotide, base
D.    cell, nucleus, chromosome, gene, nucleotide, base

3.    Which of the following correctly describes the relationship between gene, chromosome and DNA?

A.    chromosomes are polypeptides found in genes
B.    gene is a sequence of nucleotide that is found in DNA but not in chromosome
C.    DNA is made up of condensed chromosome which in turn is made up of genes
D.    chromosome is made up of condensed DNA strands which contains genes

4.    The following is a non-template strand of the DNA.


Which one of the following shows the correct sequence of the mRNA strand after transcription?


5.    DNA was extracted from the salivary glands of a fruit fly and a human cheek cell. In which way did the DNA molecules differ?

A.    in the ratio of adenine to thymine
B.    in the sequence of the nucleotides
C.    in the types of nucleotides
D.    in the type of pentose sugar


Answer: BDDBB


The eye (Receptors) Revision Structured Questions

  1. Figure 1.1 shows a section through the eye.

St Patricks Q5.PNG

Figure 1.1

(a) On Fig. 1.1, label the pupil, the iris and the optic nerve. Use label lines and the words ‘pupil’, ‘iris’ and ‘optic nerve’.

(b) Fig. 1.2 shows two front views, S and T, of a human eye in two different light intensities.

St Patricks Q5 B.PNG

Figure 1.2

(i) Suggest how the light intensity changes from S to T.

(ii)  The iris is responsible for controlling the amount of light entering the eye. The changes in the appearance of the pupil are known as the “pupil reflex”. Explain how the reflex action in Fig. 1.2 takes place. Use the following terms in your answer.

     motor neurone    relay neurone    muscle    retina    optic nerve    sensory neurone

2.  The figure below shows the change in the tension of suspensory ligament of a person who observed four different objects, one at a time within a period of 12 seconds.

P: a book on the desk 20 cm from his eyes
Q: a tree at the far corner of the garden
R: a dog running towards him
S: a car driving away from him

pasir ris crest Q4.PNG

(a) Using the letters P, Q, R and S, indicate which object is being observed during the following periods:

(i) 0 – 3 seconds

(ii) 3 – 6 seconds

(iii) 6 – 9 seconds

(iv) 9 – 12 seconds

(b) Describe how the parts of the eye produce a focussed image of object Q.

(c)(i) Name the stimulus which would cause the release of insulin.

(ii) Name the effectors that would respond to the stimulus of bright light shining into the eye.

(iii) State one way in which nervous and hormonal control are different.




St Patricks Q5 ans.PNG

(b)(i) The light intensity increases from S to T.

(ii) Photoreceptors in the retina detect the light stimulus and transmit the information in the form of nerve impulses along the sensory neuron found in the optic nerve, to the relay neurons in the brain. The relay neurons from the brain transmit nerve impulses via/along/through the motor neurons to the circular muscles in the iris (the effector), causing it to contract. When the circular muscles in the iris contract, radial muscles in the iris relax and make the pupil smaller.

2. (a) (i) S  (ii) R  (iii) P  (iv) Q

(b) As the ciliary muscles relax, the suspensory ligaments becomes taut which pulls on the lens and cause it to become thinner/less convex. This results in the the formation of a focussed image on the retina.

(c) (i) When the glucose level in the blood goes higher than normal

(ii) Iris muscles

(iii)  Nervous control involves nerve impulses but hormones are chemicals produced by glands.OR

Hormones are transported by the blood but impulses are transmitted by neurons. OR
Nervous response is short lived but hormonal response is long lived. OR

Hormonal response in usually slow but nervous response in fast. OR

Nervous response may be voluntary or involuntary but hormonal response in involuntary

The eye (Receptors) Revision MCQ Questions

1.    The diagram below shows the front view of the eye. What are the numbered structures?

o level 1.12A Pg 3 Q15 table.PNGO level 1.12A Pg 3 Q15.jpg

2.    The diagram shows a section through the eye.northland Q30.PNGWhich structure(s) refracts light rays onto the retina?

A.    P only
B.    P and R
C.    P and Q
D.    P, R and S

3.    Which diagram shows how light from a distant object falls on the back of the eye to form a clear image?

A.    o level 1.12A Pg 5 Q 21 A.jpg
B.     o level 1.12A Pg 5 Q 21 B.jpg
C.     o level 1.12A Pg 5 Q 21 C.jpg
D.     o level 1.12A Pg 5 Q 21 D.jpg

4.    The events listed occur during contraction of the pupil of the eye in response to increased light intensity.

1      Impulses pass along motor neurone    
2      Contraction of circular iris muscles    
3      Stimulation of the retina                         
4      Impulses pass along sensory neurone

Which is the correct order of these events?

A.    1 –> 4 –> 2 –> 3
B.    2 –> 1 –> 3 –> 4
C.    3 –> 1 –> 4 –> 2
D.    3 –> 4 –> 1 –> 2

5.    The eye responses to light intensity when a person enters a dark room from outside during a bright sunny afternoon. What changes occur inside the eye?

geylang Q32.PNG

6. The diagram show two sections through the eye of the same person.

serangoon Q36 A.PNG

What happens to achieve the changes from the eye in Diagram 1 to the eye in Diagram 2 under the different conditions?

serangoon Q36 B.PNG


Answer: DBCDDC

Nervous System (Reflex Action) Structured Questions

1.    A person touches a hot object and immediately pulls away his hand. the figure below shows this response.

gelang Structured question.PNG

(a)    Explain how structures A, B, C and D enable this response to occur. Identify these four structures in your answer.

(b)    The response to the hot object is a nervous response.

A hormonal response would not be as effective as a nervous response in preventing injury from the hot object. Use your knowledge of hormonal and nervous responses to suggest why.

2.    A to E below show five pathways in the nervous system of a mammal.

A. forebrain –> motor neurone –> effector (muscle)
B. sense organ –> sensory neurone –> spinal cord –> motor neurone –> effector (muscle)
C. sense organ –> sensory neurone –> brain –> motor neurone –> gland –> chemical secretion into blood stream –> effector (muscle)
D. sense organ –> sensory neurone–> brain –> motor neurone –> effector (muscle)
E. sense organ –> sensory neurone–> brain –> motor neurone –> effector (gland)

Using the appropriate letter A to E, indicate which of the actions below are brought about by the pathways above. (Each letter may be used once, more than once, or not at all)

(a) A student smells an onion and his eyes water.

(b) A student walks from the dark into a lighted room and his pupils constrict.

(c) A student sits on a drawing pin and leaps up from the chair.

(d) A student sees a swining branch approaching his eye and blink.

(e) A student decides to lift his arm.

(f) A student notices a large dog running towards him, his heart starts to beat faster.

(g) Using the appropriate letters A to E, indicate which of these nervous pathways represent:

(i) voluntary action

(ii) spinal reflex action

(iii) cranial reflex action



1 (a) Upon touching the hot object, heat receptors in the skin of the hand will be stimulated and produce nerve impulses.
The nerve impulses will be transmitted by A, the sensory neurone into the spinal cord. In the grey matter of the spinal cord, the nerve impulses are transmitted across a synapse into B, the relay/ intermediate neurone. Which in turn transmits the nerve impulses across another synapse into C, the motor neurone. The motor neurone in turn transmits the nerve impulses out of the spinal cord to D, the upper arm muscles.
Upon receiving the nerve impulses, the upper arm muscles contract, causing the hand to be pulled away from the hot object.

(b) A hormonal response involves the transport of hormones which are chemical in nature, released by a hormonal gland and transported by blood to the target organ(s) which take some time.
A nervous response on the other hand involves the transmission of nerve impulses which are electrical in nature by neurones. Hence a nervous response would be comparatively faster than a
hormonal response in general. The ability to pull the hand away quickly upon touching a hot object through the nervous response would therefore be more effective than a hormonal response in preventing injury from the hot object.

2 (a) E (b) D (c) B (d) D (e) A (f) C (g)|(i) A (ii) B (iii) E/D



Nervous System (Reflex Action) MCQ Questions

1.    The brain has many functions. What is the part that controls involuntary actions and is also a link with the spinal cord?

Marshall Perfect Guide Question 4.jpg

A.    Medulla oblongata
B.    Cerebrum
C.    Midbrain
D.    Pituitary gland

2.    The diagram shows part of a spinal reflex arc.


A.    1 –> 2 –> 3
B.    1 –> 5 –> 4
C.    3 –> 2 –> 5 –> 4
D.    4 –> 5 –> 2 –> 3

3.    Which of the following is not involved in voluntary actions?

A.    Math Neurone
B.    Relay Neurone
C.    Sensory Neurone
D.    Synapse

4.    The diagram given shows chemicals being released across a space in the spinal cord. These chemicals are ________________.

Marshall Perfect Guide Question 4.jpg

A.    waste substances
B.    neurones
C.    hormones
D.    neurotransmitters

5.    A local anaesthetic is a drug used to block nerve impulses. The diagram represents part of the nervous system. X, Y, and Z show sites where the anaesthetic can be injected. yuying Question 5.PNG

A.    at X
B.    at Y
C.    at Z
D.    at X and Z

6.    A man injures his arm in an accident. Afterwards, he can feel objects touching his hand, but he cannot move his hand away from them. What could cause this?

A.    Receptors in his hand are damaged.
B.    The nerve connection is cut only between the receptors in his hand and his central nervous system.
C.    The nerve connection is cut only between his central nervous system and the effectors in his arm.
D.    The nerve connection between the receptors in the hand and his central nervous system; and the nerve connection between the central nervous system and the effector are cut.


Answer: ACCDBC