Biology 9700/53 Oct Nov 2019 | Cambridge AS Level Past Papers With Mark Scheme

1. Effects of yeast biomass on respiration rate using TTC as a redox indicator, colorimetric absorbance measurements, and controls for experimental accuracy.

2. Comparison of respiration rates among yeast varieties (compressed, active dry, and instant yeast) and methodical evaluation of incubation conditions (pH, temperature, time) to determine optimal growth parameters.

3. Analysis of ash dieback spread in varying UK environments, percentage changes in infection rates, and genomic studies on disease tolerance using microarrays and nucleotide variation correlations.

4. Detection of gene expression in ash trees using labeled cDNA and microarrays, assessment of fluorescence intensity for expression levels, and implications for reforesting with disease-tolerant species.

5. Sampling strategies for diverse populations of ash trees, importance of proximity to diseased individuals for sample selection, and use of numeric scales for assessing disease severity.

6. Role of specific nucleotide bases in genetic tolerance to ash dieback, mechanisms by which single nucleotide changes affect pathogen resistance, and correlation of genomic variation across different ash species.