Exam 2 Study Guide: Photosynthesis, Cell Division, Genetics, Biotechnology, and Gene Expression

Photosynthesis and Respiration

Overview of Photosynthesis and Respiration

Photosynthesis and cellular respiration are complementary biological processes essential for life. Photosynthesis converts light energy into chemical energy, while respiration releases energy from organic molecules.

• Photosynthesis Reaction: The process by which plants, algae, and some bacteria convert carbon dioxide and water into glucose and oxygen using light energy.

• Respiration Reaction: The process by which cells break down glucose and oxygen to produce carbon dioxide, water, and energy (ATP).

• Equation for Photosynthesis:

$6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$

• Equation for Respiration:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}$

• Light vs Dark vs Boiled Reactions: Photosynthesis requires light; in the dark or when enzymes are denatured (boiled), the process does not occur efficiently.

• CO2 in Light vs Dark: In light, CO2 is consumed during photosynthesis; in the dark, CO2 may be produced by respiration.

Experimental Tools and Techniques

• DPIP: A blue dye used as an electron acceptor in place of NADP+; its reduction (color change) indicates photosynthetic activity.

• Spectrophotometer (Spec): Measures changes in absorbance to monitor reaction rates.

• Lamp: Provides light energy for photosynthesis experiments.

• Pipettes: Used for accurate measurement and transfer of liquids.

• Vernier Equipment and CO2 Chamber: Used to measure CO2 levels, indicating rates of photosynthesis or respiration.

Graphical Representation

• Graphs typically show the rate of photosynthesis under different conditions (light, dark, boiled), with the highest rate in light and lowest in boiled samples.

Cell Division: Mitosis and Meiosis

Phases of Mitosis and Meiosis

Mitosis and meiosis are processes of cell division that ensure genetic continuity and diversity.

• Mitosis: Produces two genetically identical diploid cells for growth and repair.

• Meiosis: Produces four genetically unique haploid gametes for sexual reproduction.

Phases of Mitosis

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

Phases of Meiosis

• Meiosis I: Homologous chromosomes separate (includes Prophase I, Metaphase I, Anaphase I, Telophase I)

• Meiosis II: Sister chromatids separate (includes Prophase II, Metaphase II, Anaphase II, Telophase II)

Key Terms

• Haploid (n): One set of chromosomes.

• Diploid (2n): Two sets of chromosomes.

• Chromosome: DNA molecule with genetic material.

• Chromatid: One of two identical halves of a duplicated chromosome.

Genetic Variability

• Crossing Over: Exchange of genetic material between homologous chromosomes during Prophase I of meiosis.

• Independent Assortment: Random distribution of homologous chromosomes during Metaphase I.

Microscopy in Cell Division

• Onion root tip and white fish blastula slides are used to observe mitosis phases.

• Proportion of time spent in each phase can be estimated by counting cells in each stage.

Mendelian Genetics

Genetic Crosses

• Hybrid Crosses: Mating between individuals with different alleles.

• Test Crosses: Cross between an individual with an unknown genotype and a homozygous recessive individual.

• Dihybrid Crosses: Crosses involving two traits.

Genotype and Phenotype Ratios

• Genotype Ratio: The ratio of different genetic combinations (e.g., 1:2:1 for Aa x Aa).

• Phenotype Ratio: The ratio of observable traits (e.g., 3:1 for dominant:recessive in monohybrid cross).

Biotechnology: Gene Recombination and Analysis

Gene Recombination

• Process of combining DNA from different sources to create recombinant DNA.

Restriction Enzymes

• Enzymes that cut DNA at specific sequences, enabling gene cloning and analysis.

Plasmids

• Circular DNA molecules used as vectors to carry foreign genes into host cells.

Gel Electrophoresis

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

• DNA is negatively charged and moves toward the positive electrode; smaller fragments migrate further.

DNA Isolation and Restriction Digest

• DNA is extracted from cells, digested with restriction enzymes, and analyzed by gel electrophoresis.

• Predicting fragment sizes and interpreting gel images are key skills.

Experimental Tools

• Pipettes: For precise liquid handling.

• Gel Electrophoresis Apparatus: For running DNA samples through agarose gel.

Gene Expression and Regulation

Central Dogma of Biology

• Describes the flow of genetic information: DNA → RNA → Protein.

Inducible Genes

• Genes that are expressed only in the presence of specific molecules (inducers).

Experimental Inducers and Substrates

• IPTG: A chemical analog of lactose that induces gene expression by inactivating the repressor protein.

• ONPG: A substrate that, when cleaved by β-galactosidase, produces a yellow color, indicating gene expression.

Interpreting Results

• Gene expression is detected by color change (ONPG cleavage) and can be quantified using a spectrophotometer.

• Graphs show increased absorbance or color intensity when gene expression occurs.

Experimental Tools

• Spectrophotometer: Measures absorbance to quantify gene expression.

• Pipettes: For accurate reagent handling.

Additional info: Academic context and definitions have been added to expand on the brief points in the original study guide. Where specific details were missing, standard biological knowledge was used to provide a comprehensive overview.