IGCSE Biology Paper-1: Specimen Questions with Answers 182 - 183 of 208

Question 182

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Question

MCQ▾

The diagram is showing a starch molecule.

A Starch Molecule

A Starch Molecule

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Which diagram shows this molecule after it has been completely digested?

A Starch Molecule

A Starch Molecule

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Choices

Choice (4)
a.B
b.D
c.A
d.C

Answer

b.

Explanation

Amylase, which is commonly found in saliva and germinating seeds. It catalyzes the breakdown of starch. When amylase reacts with starch, it cuts off the disaccharide maltose (two glucose molecules linked together). As the reaction progresses, less starch will be present and more sugar (maltose) will be present. The activity of amylase can be observed by using iodine. Because iodine reacts with starch to form a dark brown/purple colour. As amylase breaks down starch, less and less starch will be present and the colour of the solution (if iodine is added) will become lighter and lighter.

Less Starch will be Present

Less Starch Will be Present

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Question 183

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MCQ▾

A mouse with grey hair breeds with a mouse with white hair, producing offspring with genotypes Gg, Gg, gg and gg. (G represents the dominant allele for grey hair, and g represents the recessive allele for white hair).

Which correctly describes the genotypes of the parents?

Choices

Choice (4)
a.both heterozygous
b.both homozygous dominant
c.one heterozygous and one homozygous recessive
d.one heterozygous and one homozygous dominant

Answer

c.

Explanation

A mouse with grey hair breeds with a mouse with white hair, producing offspring with genotypes Gg, Gg, gg, and gg. For determining expected genotype apply punnet square. The result obtained from Gg crossing with gg.

The result obtained from Gg crossing with ggThe result obtained from Gg crossing with gg
Gg
gGggg
gGggg