2.1 The diagram below shows part of a process involved in the production of a protein - NSC Life Sciences - Question 2 - 2019 - Paper 2

The nitrogenous bases Z are UGG.

The nitrogenous bases 1, 2, and 3 are TGG.

The DNA base triplet that codes for X is TGG.

The type of dominance shown by cross 4 is co-dominance. This occurs because the offspring display a phenotype that shows characteristics of both parent phenotypes, indicating that both alleles contribute equally to the phenotype.

The shell colour controlled by the recessive allele is black.

In cross 1, both parents are yellow which produces a phenotypic ratio of 27:9, and black does not appear in the phenotype of the offspring. This indicates that yellow is dominant over black.

The dominant phenotype is spotted.

This can be concluded as spotted frogs produced more spotted offspring (150) compared to the non-spotted ones (50). Therefore, the ratio suggests that spotted is dominant.

The genetic cross can be represented as follows:

P1: Dd (spotted) x dd (without spots)

Gametes:

• Dd produces D and d
• dd produces d

F1 Generation:

• Genotypes: 50% Dd (spotted), 50% dd (without spots)
• Phenotypes: 50% spotted, 50% without spots.

The independent variable in this investigation is the type of antibiotic.

1. Environmental conditions, such as temperature and humidity.
2. Age of the piglets.

1. The study was conducted over a period of six months.
2. A large sample size of 100 piglets was used.

I would recommend antibiotic B for controlling E. coli in piglets, as it shows a higher average resistance.

The results indicate that the average percentage resistance of E. coli to antibiotic A was lower initially, which suggests that some bacteria were naturally resistant. Over time, resistance increased due to selective pressures, demonstrating the bacteria's ability to adapt.