Lab Practical Review: Cellular Respiration, Photosynthesis, GMOs, PCR, Gel Electrophoresis, and Scientific Communication

Unit 8: Cellular Respiration, Photosynthesis, and Introduction to GMOs

Variables Affecting the Rate of Photosynthesis

• Light Intensity: Increased light generally raises the rate of photosynthesis up to a certain point, after which it plateaus.

• Carbon Dioxide Availability: CO2 is a substrate for photosynthesis; higher concentrations can increase the rate until other factors become limiting.

Locations of Photosynthesis and Cellular Respiration

• Photosynthesis: Occurs in the chloroplasts of plant cells.

• Cellular Respiration: Occurs in the mitochondria of both plant and animal cells.

Chemical Reactions of Photosynthesis and Cellular Respiration

• Photosynthesis:

$6\ \mathrm{CO}_2 + 6\ \mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\ \mathrm{O}_2$

• Cellular Respiration:

$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\ \mathrm{O}_2 \rightarrow 6\ \mathrm{CO}_2 + 6\ \mathrm{H}_2\mathrm{O} + \text{ATP (energy)}$

• Reactants and Products:

  • Photosynthesis Reactants: CO2, H2O, light energy

  • Photosynthesis Products: Glucose (C6H12O6), O2

  • Cellular Respiration Reactants: Glucose, O2

  • Cellular Respiration Products: CO2, H2O, ATP

Experimental Results and Relationships

• CO2 Production: Increases after exercise due to higher cellular respiration rates.

• Relationship: Photosynthesis and cellular respiration are complementary; the products of one are the reactants of the other.

Phenol Red Indicator

• Acidic: Yellow

• Neutral: Red

• Basic: Pink/Magenta

Chlorophyll Absorbance

• Chlorophyll a: Highest absorbance in blue (~430 nm) and red (~662 nm) wavelengths.

• Chlorophyll b: Highest absorbance in blue (~453 nm) and red (~642 nm) wavelengths.

Additional info: Absorbance spectra help explain why plants appear green—they reflect green light.

Unit 9: Plant DNA Preparation for GMO Detection

Gene Structure

• Sections of a Gene: Promoter, coding region (exons and introns), terminator.

Genetically Modified Organisms (GMOs)

• Definition: Organisms whose genetic material has been altered using genetic engineering techniques.

Promoters Used in GMO Labs

• Common Promoters: CaMV 35S (from Cauliflower Mosaic Virus), NOS (nopaline synthase from Agrobacterium).

DNA Extraction Process

• Vortex: Mixes samples thoroughly to break up cells.

• Chelex Resin: Binds metal ions that could degrade DNA, protecting it during extraction.

• Supernatant: The liquid above the pellet after centrifugation, contains DNA.

• Cell Debris Pellet: Solid material at the bottom, contains cell fragments.

Controls in Experiments

• Positive Control: Ensures the procedure works by using a sample known to contain the target DNA.

• Negative Control: Ensures no contamination; should not produce a result if the process is clean.

Unit 10: PCR for GMO Detection in Plant DNA

Polymerase Chain Reaction (PCR)

• Definition: Technique to amplify specific DNA sequences, making millions of copies from a small sample.

• Uses: Detecting GMOs, diagnosing diseases, forensic analysis.

PCR Components

• DNA Template: The DNA sample containing the target sequence.

• Primers: Short DNA sequences that initiate DNA synthesis at specific sites.

• PCR Master Mix: Contains nucleotides, buffer, and other components needed for the reaction.

• Taq Polymerase: Heat-stable enzyme that synthesizes new DNA strands.

Steps of PCR

1. Denaturation: DNA strands are separated by heating (usually ~94°C).

2. Annealing: Primers bind to target sequences as the temperature is lowered (~50-65°C).

3. Extension: Taq polymerase extends the primers to synthesize new DNA (~72°C).

Rate of DNA Amplification

• Each cycle doubles the amount of DNA: $2^n$ after n cycles.

GMO Benefits and Concerns

• Benefits: Increased crop yield, pest resistance, improved nutrition.

• Cons/Concerns: Environmental impact, potential allergenicity, ethical issues.

Unit 11: Gel Electrophoresis for GMO Detection and Garlic Root Mitosis

Stages of Mitosis

• Interphase: Cell grows and DNA replicates (G1, S, G2 phases).

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at the cell's equator.

• Anaphase: Sister chromatids separate to opposite poles.

• Telophase: Nuclear envelopes reform around chromosomes.

• Cytokinesis: Division of the cytoplasm, forming two cells.

Gel Electrophoresis

• Definition: Technique to separate DNA fragments by size using an electric field.

• Parts: Gel matrix (usually agarose), buffer, electrodes, wells for loading samples.

• DNA Charge: DNA is negatively charged due to its phosphate backbone.

• Loading: Samples are loaded at the negative electrode (cathode); DNA migrates toward the positive electrode (anode).

• Fragment Movement: Smaller DNA fragments move faster and farther through the gel than larger ones.

Primer Locations

• Plant Primer: Targets plant-specific DNA sequences.

• CaMV 35S Primer: Detects the Cauliflower Mosaic Virus promoter, common in GMOs.

• NOS Primer: Detects the nopaline synthase terminator, also common in GMOs.

Calculating Percent of Total Cells Counted

• Formula: $\text{Percent} = \frac{\text{Number of cells in a stage}}{\text{Total cells counted}} \times 100$

Unit 12: Presenting Scientific Data

Methods of Scientific Communication

• WIP Format: "Work in Progress" presentations for sharing ongoing research.

• Poster Presentations: Visual summaries of research for conferences and meetings.

• Written Lab Reports/Journal Articles: Formal documentation of experiments and findings for publication.

Additional info: Effective communication is essential for scientific progress and peer review.