State the Hardy-Weinberg principle and explain its assumptions. What are the implications of homozygosity and heterozygosity?

The phenotypic frequencies are:

• White: $\boxed{\text{0.25}}$
• Pink: $\boxed{\text{0.45}}$
• Red: $\boxed{\text{0.30}}$

ii. Allele frequencies in the population (04 marks)

Total alleles = $2 \times \text{Total plants} = 2 \times 1000 = 2000$

Number of R alleles = $(2 \times \text{Number of Red}) + (1 \times \text{Number of Pink})$
Number of R alleles = $(2 \times 300) + (1 \times 450) = 600 + 450 = 1050$

Number of W alleles = $(2 \times \text{Number of White}) + (1 \times \text{Number of Pink})$
Number of W alleles = $(2 \times 250) + (1 \times 450) = 500 + 450 = 950$

The allele frequencies are:

• Frequency of R ($p$): $\boxed{\text{0.525}}$
• Frequency of W ($q$): $\boxed{\text{0.475}}$

iii. Genotypic frequencies in the population (04 marks)

The genotypic frequencies are:

• Frequency of RR: $\boxed{\text{0.30}}$
• Frequency of RW: $\boxed{\text{0.45}}$
• Frequency of WW: $\boxed{\text{0.25}}$

QUESTION 5

a) State the multiple gene hypothesis. (04 marks)

The multiple gene hypothesis, also known as polygenic inheritance, states that many genes, each contributing a small, additive effect, determine a single phenotypic trait. This interaction of multiple genes often results in continuous variation of the trait within a population, rather than discrete categories.

b) What characteristics distinguish quantitative traits from qualitative traits. (08 marks)

Qualitative traits are characteristics that fall into distinct categories and are typically controlled by one or a few genes, with minimal environmental influence. Examples include blood type (A, B, AB, O) or flower color (red, white).

Quantitative traits are characteristics that show continuous variation across a range, often measured on a scale, and are influenced by multiple genes (polygenic inheritance) as well as significant environmental factors. Examples include human height, weight, or crop yield.

c) Besides, quantitative inheritance, discuss four non-Mendelian inheritance patterns. (08 marks)

1. Incomplete Dominance: In this pattern, the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes. For example, a cross between a red-flowered plant and a white-flowered plant might produce pink-flowered offspring.
2. Codominance: Both alleles in a heterozygote are fully and distinctly expressed, without blending. A classic example is the ABO blood group system in humans, where individuals with AB blood type express both A and B antigens on their red blood cells.
3. Multiple Alleles: This occurs when there are more than two possible alleles for a single gene within a population. While an individual can only carry two alleles, the population gene pool contains several variants. The ABO blood group system is also an example of multiple alleles (Iᴬ, Iᴮ, i).
4. Epistasis: This is a phenomenon where the expression of one gene is affected (masked or modified) by one or more other genes at different loci. For instance, in Labrador retrievers, one gene determines coat color (black or brown), but another gene determines whether the color is deposited in the fur at all, leading to yellow labs regardless of the first gene's alleles.