genetics - biology form 4 topical questions and answers.pdf...

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GENETICS
1. 1989 Q13 P1
In an experiment, a variety of garden peas having a smooth seed coat was crossed with
a variety with a wrinkled seed coat. All the seeds obtained in the f generation had a
smooth seed coat. The f generation was selfed. The total number of f2 generation was
7324.
(a) Using appropriate letter symbols. Work out the genotype of the f1 generation
(b) From the information above, work out the following for the f2 generation
2. 1990 Q2 P1
The figure below is a structural diagram of a portion from anucleic acid stand.
-----S – P – S – P – S – P – S -----
C G U
(a) Giving a reason, name the nucleic acid to which the portion belongs
C
…………………………………………………………………………………………………
…………………………………………………………………………………………………
(b) Write down the sequence of bases of a complementary strand to that show above
…………………………………………………………………………………………………
…………………………………………………………………………………………………
3. 1990 Q12 P1
A garden pea plant having green round seeds was crossed with another garden pea plant
NAME INDEX NUMBER
SCHOOL DATE

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having yellow wrinkled seeds. The seeds produced in the f1 generation were all green
and round
(a) State the dominant traits in these plants
………………………………………………………………………………………………
(b) If D and d represents genes that determine seed colour, while T and T represents
genes that determines seed texture;
(i) Give the genotype of each parent plant
(ii) Give a reason for your answer (b) (i) above
……………………………………………………………………………………………
……………………………………………………………………………………………
(iii) Work out the genotypes of the F1 generation.
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
(iv) In the table below, work out the progeny between the F1 generation and a plant
having yellow wrinkled seeds
F1/plant DT Dt DT
dt DdTt Ddtt ddtt
dt DdTt Ddtt ddtt
dt DdTt Ddtt Ddtt
dt DdTt Ddtt ddtt
(v) What was the phenotypic ratio of the progeny in (b) (iv) above?
dt
ddTt
ddTt
ddTt
ddTt