(a) List three transmittable characters in: (I) human beings (ii) plants (b) State three ways in which genetics has contributed to improvement of agricultur...

(a) Transmittable (heritable) characters

(i) In human beings:

• Colour of the eyes (eye colour)
• Colour of the skin
• Blood group (A, B, AB, O)

(ii) In plants:

• Height of the plant (tallness or shortness)
• Colour of the flower
• Shape or colour of the seed

(b) Three ways genetics has contributed to the improvement of agriculture

• Production of improved (high-yielding) varieties: selective breeding and hybridisation have produced crops and animals that give higher yields of grain, milk, meat or eggs.
• Development of disease- and pest-resistant varieties: genetics is used to breed crops and livestock that resist diseases and pests, reducing losses.
• Breeding for desirable qualities and adaptation: production of varieties that are early maturing, drought resistant, or tolerant of poor soils, and animals with better feed conversion (also improved food quality).

(c) Cross between a homozygous tall parent and a homozygous short parent

Let the allele for tallness be T (dominant) and for shortness be t (recessive).

Parental genotypes: tall = TT; short = tt.

Gametes: T from the tall parent; t from the short parent.

First filial (F₁) generation: all offspring are Tt (heterozygous) and are therefore all tall, since T is dominant. Ratio: 100% tall.