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My name is Poon Cheng Moh. I have been teaching biology in SMK(P) Raja Zarina, Port Klang for 26 years. I sincerely hope that this blog on SPM Biology will be useful to both teachers and students.

Saturday, August 11, 2012

Answers to Hands-on Pg 65-69


Objective Questions
1
A
9
D
2
B
10
D
3
B
11
A
4
A
12
D
5
D
13
C
6
B
14
B
7
B
15
C
8
A
16
C

Structured Questions
Section A
1. (a) (ii) Tall plants with coloured flowers
(b) (i) Dihybrid cross
(ii) TtCc
(d)(i)
Gametes
TC
Tc
tC
tc
tc
TtCc
Ttcc
ttCc
ttcc

(ii) A plant which is heterozygous for tallness and coloured flowers has the genotype TtCc. The plant produces four types of gametes, TC, Tc, tC and tc. When the plant is crossed with another plant which is homozygous recessive, the gametes combine at random to produce plants with TtCc, Ttcc, ttCc and ttcc as their genotypes.
(e) To obtain consistent results as pure-breeding plants are able to produce offspring which have received identical genes from the parents. When self-fertilised, they are able to produce offspring having exactly the genes they have inherited.

2. (a) (i) Genes are carried on the sex chromosomes and passed down to the next generation.
(ii) Usually are carried on the X chromosome and it mostly affects the males
(b) Bakri’s mother must be a carrier with the genotype XHXh in which ‘h’ is the recessive gene for haemophilia. Bakri inherits Xh from his mother and the Y chromosome from his father.
(c) One of them inherits XH from her father and XH from her mother. The other one inherits XH from her father and Xh from her mother. Both are normal but genotypically, one of them is a carrier.
(d) Males are determined by the presence of the X and Y chromosomes. Sex-linked genes are absent in the Y chromosomes. Therefore, the presence of one sex-linked gene in the X chromosome will affect the male as compared to the female who
needs genes to be present in both X chromosomes for her to be affected.
(e)
Gametes
Xh
Y
XH
XHXh
XHY
Xh
Xh Xh
XhY
(f) 100%

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