Activity 11.1 (Form 5 Biology Textbook Exercise and Answer)

Activity 11.1:
To carry out an experiment using beads to illustrate monohybrid fertilisation by analogy

Two black plastic bags, 100 red beads, 100 white beads

Red bead represents dominant allele for red-coloured flowers (R)
White bead represents recessive allele for white-coloured flower (r)

Fertilisation between two heterozygous or hybrid plants of first filial generation F1:

1. Place 50 red beads and 50 white beads into the first black plastic.
This represents pea plants with coloured flowers which are heterozygous.

2. Repeat step 1 with a different black plastic bag.

3. Both plastic bags are shaken to mix the beads well.

4. Without looking into the plastic bags, place a hand inside the first plastic bag and remove one bead. Remove another bead from the second plastic bag.

5. Place both beads on the table. Both beads represent combination of two gametes.

6. Record the probability of genotype and phenotype in F2 generation in a table.

7. Return the two beads into their respective plastic bags.

8. Ensure that the beads are returned to the correct bags.

9. Repeat steps 3 to 7 for a total of 50 times.

10. Count the total combinations of genotype and phenotype that are produced.

1. Which type of inheritance is shown by the characteristic studied in the above experiment?

2. (a) Is the result obtained in accordance with the expected ratio of 3 : 1?
(b) Explain your answer.

3. Why is the bead returned into its plastic bag after each observation was recorded?

4. Suggest ways to improve the accuracy of the experiment.

1. Monohybrid inheritance

2.(a) Yes

2. (b)
The phenotypic ratio follows the expected ratio of Mendel’s First Law, which is 3 : 1. 
The dominant phenotype is three times to the recessive phenotypes. This is because the organism characteristic is determined by a pair of alleles which get separated, and then each allele is carried by a gamete. A dominant allele will show its trait when present.

3. To ensure that each bag will always have a total of 100 beads (50 red and 50 white). This is to ensure that the population is not disturbed after each count.

4. By adding more but equal number of each coloured beads.

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