MUSINGU SCHOOL
FORM 3 BIOLOGY REVISION QUIZ ON GENETICS: 2012
1. What is Genetics?
(1 mk)
2. State the first law of inheritance
(2 mks)
3. Distinguish between continuous and discontinuous variation. Give an example of each (4 mks)
4. What is meant by the following terms?
a. Test cross
(2 mks)
b. Allele
(1 mk)
c. Hybrid vigour
(2 mks)
5. In rabbits, the allele for long ears is dominant to the allele for short ears. What percentage of
offspring would have short ears from a cross between a heterozygous long-eared rabbit and a
short-eared rabbit? Use letter E to represent the allele for long ears
(4 mks)
6. In a breeding experiment, a plant with red flowers was crossed with another one with white
flowers. All the offspring had pink flowers. Using the letter R to represent the gene for red and
letter W for the gene of white colour:
i.
Work out the genotype of the F1 generation
(5 mks)
ii.
What will be the phenotypic ratio of F2 generation if the F1 generation was selfed? (2
mks)
iii.
What type of genetic inheritance is shown by the experiment above?
(1 mk)
7. A haemophiliac man marries a carrier woman for haemophilia. What is the probability that their
first born daughter will be haemophilic? Show your working
(5 mks)
8. Why is haemophilia and colour blindness more frequent in males than female humans? (2 mks)
9. Briefly explain how the following mutations occur
i.
Translocation
(2 mks)
ii.
Inversion
(2 mks)
iii.
Insertion
(2 mks)
10. Give 4 applications of genetic knowledge to modern society
(4 mks)
11. Yellow fur colour in mice is controlled by a dominant allele Y. T he normal grey fur colour is
controlled by the recessive gene. Homozygous mice for yellow fur colour abort shortly before
birth. However, heterozygous mice for yellow colour survive. Heterozygous yellow mice were
crossed with each other. Using a genetic cross, determine the phenotypic ratio and the genotypic
ratio of the offspring produced from this cross
(6 mks)
12. In a family with four children, the father had blood group AB and the mother had blood group B
(heterozygous)
i) State the possible genotypes of the children
(1 mk)
ii) Name the type of inheritance exhibited by these results
(1 mk)
iii) With a reason, state the genotype of the child who can receive blood from any member of the
family
(2 mks)
13. In a certain plant species, which is normally green, a recessive gene for colour (n) causes the
plant to be white. When present in homozygous state, such plants die at an early stage. The
plants are pale green in colour when in heterozygous state and grow to maturity
a) Give a reason for the early death of plants with homozygous recessive gene
(1 mk)
b) If a normal green plant was crossed with the pale green plant, what would be the genotypes
of the F1 generation?
(2 mks)
c) If seeds from the heterozygous plants were planted and the resulting plants crossed, work out
the phenotypic ratio of plants that would grow to maturity
(3 mks)
d) Explain the occurrence of the pale green colour in the heterozygous plants
(1 mk)
1
14. John and Mary are married and have four children. Three of the children have normal skin
pigmentation while one child is an albino. Using letters A to represent the gene for normal skin
pigmentation and letter a to represent the gene for albinism;
i) State the parental genotypes
(2 mks)
ii) Work out the genotypes of the normal pigmented children
(3 mks)
15. Black colour is due to a dominant gene in rats. Two black rats were crossed and their F 1
generation was in the ratio of 3 black: 1 white. Using letter B to represent the gene for black
colour and b for white colour, give the:
a) i) Genotypes of the parents
(2 mks)
ii) Gametes of the parents
(2 mks)
iii) Genotypic ratio of the F1 generation
(3 mks)
b) What is meant by the term test cross as used in genetics?
(1 mk)
16. A farmer crossed a black bull and a white cow and discovered that the resulting calf had black
and white spots which were equally distributed. He concluded that the genes for colour are
codominant
a) Using letter B to represent black colour and W for white colour, write down the parental
genotypes
(1 mk)
b) Write down the genotypes for F1 calves
(1 mk)
c) If F1 offspring were crossed, work out a cross between the F1 cattle
(4 mks)
d) Give the phenotypic ratio of the F2 cattle
(1 mk)
e) If the farmer wanted white cows only in all generations, select the genotype that he would
use in subsequent crosses
(1 mk)
17. Haemophilia is a sex-linked characteristic. A normal man married a carrier woman for this
characteristic
a) Work out the nature of the offspring born to these parents (use letter H for normal and h for
haemophilia)
(3 mks)
b) What is the probability of one of the sons being a haemophiliac?
(1 mk)
c) What would be the expected parents’ genotypes for one of their daughters to be haemophilic?
(1 mk)
d) Explain why there are no carrier males
(1 mk)
18. Write the type of gene mutation represented by the following analogues:
a) Intended message: BRING THERMOS ON OUTING
Actual message: BRING MOTHERS ON OUTING
b) Intended message: PLEASE SAY WHERE YOU ARE
Actual message: PLEASE STAY WHERE YOU ARE
19. The following diagrams represent examples of chromosomal mutations:
A
B
C
D
E
H
A
B
C
D
E
A
B
A
B
C
D
E
I
II
I
A
B
C
E
D
II
X
Y
Name the types of chromosomal mutations represented by X and Y
(2 mks)
20. In an experiment, a variety of garden peas having a smooth seed coat was crossed with a variety
having wrinkled coat. All the plants obtained in the F1 generation had a smooth seed coat. F1
2
generation plants were selfed. The total number of plants with smooth seed coat in the F2
generation was 7323
a) Using letter R for smooth seed coat, work out the genotype of the F2 generation
(4 mks)
b) From the information in a) above, work out the following for F2 generation:
i) Genotypic ratio
(1 mk)
ii) Phenotypic ratio
(1 mk)
iii) Total number of plants with wrinkled seed coats
(2 mks)
21. Broad and thin lips in humans are characteristics that are inherited. When a homozygous broadlipped man is crossed with a homozygous thin-lipped woman, all the children in the family are
broad-lipped. In a particular family, a woman who is heterozygous for broad lips is married to a
man whose parents were both thin-lipped. Using letter B to represent genes for broad lips:
a) Work out the genotypic ratio of the children in that family
(6 mks)
b) What is the phenotypic ratio of the children in a) above?
(1 mk)
c) Distinguish between gene mapping and sequencing of genes
(2 mks)
22. In cats, sex is determined by X and Y chromosomes in the same way as in humans. On gene for
coat colour in cats is present on the X chromosome but not on the Y chromosome. This gene
has two alleles, orange (B) and black (b) and the X chromosome bearing the B allele is
represented by XB while the one bearing the b allele by Xb. Female cats that are homozygous for
the Xb allele have black coats while female cats that are heterozygous have tortoiseshell coats
(orange with dark patches)
a) Give the genotype for:
i) A female cat with tortoise coat
(1 mk)
ii) A male cat with an orange coat
(1 mk)
iii) A male cat with a black coat
(1 mk)
b) A black-coated male cat was mated with a tortoiseshell-coated female cat. Use a genetic
diagram to explain what would be the expected ratios of the genotypes and the phenotypes
of the kittens that could be produced by this cross
(5 mks)
23. In Drosophila spp, the gene for wing length is sex-linked. The allele for normal wings is
dominant over the short wings. A short-winged male fly was crossed with a homozygous
normal-winged female. The F1 offspring were then inbred through several generations under
ultraviolet light in a laboratory. After several generations, wingless flies appeared amongst the
progeny. In addition, many eggs laid by the mated females would not hatch
a) Work out and then state what portion of the F1 flies exhibited the dominant phenotype (3
mks)
b) From the descriptions given:
i) Name the process that caused the appearance of the wingless flies
(1 mk)
ii) State two general effects of the process named in b) i) above
(2 mks)
24. A primary school girl whose father is a well-known politician accused a Form 4 boy of being
the biological father to her baby. The girl has blood group B while the baby has blood group O.
The accused boy has blood group AB. Is the accusation valid? Explain your answer
(4 mks)
25. Name the two types of mutations represented below:
A
B
C
D
E
F
P
B
C
D
D
E
F
i) Original strand
ii) Mutated strand
26. In Andulusian chicken, the genes for black feathers and white feathers are co-dominant. A white
chicken was crossed with a black chicken; all the F1 chicks were blue-feathered. Using the
symbols B and W to represent the genes for black colour and white colour respectively:
a) What is the phenotypic ratio if the F1 offspring were selfed?
(3 mks)
3
b) State the possible genotypes when a black-feathered cock is crossed with a blue-feathered
hen
(2 mks)
27. In an experiment, the approximate distribution of blood groups in a sample of 100 people in a
population was investigated. The results are shown in the table below.
Blood Group
A
B
AB
O
Frequency
26
20
4
50
Rhesus +ve
22
18
3
42
Rhesus -ve
4
2
1
8
a) Calculate the percentage of Rhesus negative (Rh-ve) individuals in the population
(2 mks)
b) Account for:
i) The large number of blood group O individuals in the population
(3 mks)
ii) The small number of individuals with blood group AB
(2 mks)
28. Give and briefly explain one of the human diseases/disorders associated with non-disjunction
type of mutation
(4 mks)
29. A certain species of a flowering plant relies entirely on sexual reproduction for propagation. The
chromosome number of a cell in the ovarian wall is 16. State the chromosome number of:
a) The pollen tube nucleus -------------------------------------------------------------------------- (1 mk)
b) A cell of the endosperm -------------------------------------------------------------------------- (1 mk)
30. A true-breeding purple maize variety was cross-pollinated with a true-breeding yellow maize
variety. The offspring produced all purple fruits. The plants grown from these F1 generation
grains were interbred among each other. A typical cob of F2 generation is shown below where
the yellow fruits are shaded while the purple ones are un-shaded
a) i) In terms of flowers only, state why it is easier to work out genetic crossings using maize (1
mk)
ii) Count separately the yellow and purple grains and therefore find the ratio of purple grains
to yellow grains
(1 mk)
b) Using appropriate symbols, work out a genetic cross for F2 generation
(4 mks)
c) From the above information, give the dominant gene
(1 mk)
d) State two practical applications of genetics in identity determination
(2 mks)
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