Farm animals have sex chromosomes, known as gonosomes, and body chromosomes, known as autosomes. Horses have 64 chromosomes and goats have 60. Indicate EACH of the following: (a) The number of sex chromosomes in goats (b) The number of pairs of autosomes in horses

4.5.1

a) The number of sex chromosomes in goats is always 2 (one pair).

b) Horses have 64 chromosomes in total. Since 2 are sex chromosomes, there are $64 - 2 = 62$ autosomes. The number of pairs of autosomes is $\frac{62}{2} = 31$.

a) $\boxed{\text{2}}$

b) $\boxed{\text{31 pairs}}$

4.5.2

a) When a ram (XY) is mated with an ewe (XX), the possible offspring genotypes are XX (female) and XY (male).

$$\text{Percentage chance of male offspring} = \frac{1}{2} \times 100\% = 50\%$$

b) The ratio of male to female offspring is 1:1.

a) \boxed{\text{50%}}

b) $\boxed{\text{1:1}}$

4.6.1
Heritability is the proportion of the total phenotypic variation in a trait within a population that is due to genetic differences among individuals.

4.6.2

a) A qualitative characteristic is one that is expressed as a distinct category and is not typically measured numerically.

b) A quantitative characteristic is one that can be measured numerically and shows continuous variation.

a) $\boxed{\text{Eye colour}}$

b) $\boxed{\text{Milk production / Fleece weight}}$

4.6.3
The heritability for milk production is 40%. The total variation in a trait is due to genetic and environmental factors.

$$\text{Environmental effect} = 100\% - \text{Heritability}$$ $$\text{Environmental effect} = 100\% - 40\% = 60\%$$

\boxed{\text{60%}}

4.6.4
Heritability indicates the extent to which a trait is genetically determined. A higher heritability means that the estimated breeding value (EBV) will be a more accurate predictor of an animal's genetic merit for that trait, leading to more effective selection for improvement.

4.7.1

• Genetic modification allows for the introduction of specific genes from any organism, enabling traits not possible through traditional breeding.
• It is generally faster and more precise than traditional breeding, as specific genes can be targeted and inserted without introducing undesirable genes.

4.7.2

• Potential for gene flow to wild relatives, which could lead to the creation of "superweeds" or impact biodiversity.
• Possible harm to non-target organisms (e.g., beneficial insects) due to toxins produced by GM crops.