**Activity 11.1**:

**Aim**

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

**Apparatus**

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

**Analogy**

Red bead represents dominant allele for red-coloured flowers (R)

White bead represents recessive allele for white-coloured flower (r)

**Procedure**

Fertilisation between two heterozygous or hybrid plants of first filial generation F

_{1}:

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.

**Discussion**

**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.

**Answer**:

**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.