(a)   Define the following terms.

          (i)  Monohybrid cross.

          (ii)  Mutation.

          (iii) Homozygous. (3,3,2 marks)

(b)   State the causes of mutation. (4 marks)

(c)   In a certain variety of squirrels, the fur colour is either grey or black. When a pure breeding black squirrel is crossed with a pure breeding grey squirrel, all the offspring produced had grey fur. When these offspring were allowed to interbred, the following results were obtained; 428 squirrels with grey fur and 152 squirrels with black fur.

Using appropriate symbols and diagrams explains the genetic of these crosses. (6 marks)

(d)   How does bread mould reproduces asexually? (2 marks)

                                                               (Total = 20 marks)

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(a)   Define the following terms: (3,3,2 marks)

            (i)     Monohybrid cross.

A monohybrid cross is a genetic cross between two individuals in which only one character or trait is studied.

           (ii)    Mutation.

A mutation is any natural or induced change in the genetic make-up of an organism.

FURTHER EXPLANATIONS

There exist generally 2 types of mutation according the cell which is mutating: germ cell mutation and somatic mutation. There also exist 2 others for how the mutation is taking place: gene mutation and chromosomal mutation. No matter be the case, the bottom line is the fact that, any change in the genetic make-up of an organism is a mutation.

           (iii)  Homozygous

This is a condition whereby both alleles that make up a gene are similar e.g. “AA” or “aa”.

(b)   State the causes of mutation.   (4 marks)

• High energy radiation like UV rays, X rays, gamma rays etc.
• Cosmic rays from outer space.
• Radioactive radiations.
• Chemicals like mustard gas, caffeine, formaldehyde, cocaine etc.
• Tobacco, pesticides, drugs etc.
• Artificial or man induced

 

(c)   In a certain variety of squirrels, the fur colour is either grey or black. When a pure breeding black squirrel is crossed with a pure breeding grey squirrel, all the offspring produced had grey fur. When these offspring were allowed to interbred, the following results were obtained; 428 squirrels with grey fur and 152 squirrels with black fur.

Using appropriate symbols and diagrams explains the genetic of these crosses (6 marks)

Let the dominant allele for skin colour (Grey) be G

Let the recessive allele for skin colour (Black) be g

(d)   How does bread mould reproduces asexually?    (2 marks)

Breadmould reproduces asexually by sporulation. The mould grows a sporangium that contains spores. When the spores mature, the sporangium burst. Releasing the spores which will later germinate to hyphae of bread mould.

                                                 (Total = 20 marks)

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THE END!!!

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You can check out:

Question one here: O/L Biology 2019 question one 2019 Answer | Alpha Study Group (alstug.com)

Question two here:O/L Biology 2019 question Two 2019 Answer | Alpha Study Group (alstug.com)

Question three here: O/L Biology 2019 question Three 2019 Answer | Alpha Study Group (alstug.com)

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