General Biology: Photosynthesis, Cell Cycle, Genetics, and Inheritance Study Guide

Chapter 10: Photosynthesis and Energy in Plants

Photosynthesis Overview

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water.

• Site of Photosynthesis: Photosynthesis primarily occurs in the chloroplasts of plant cells, especially in the mesophyll cells of leaves.

• Stomata: Small openings on the leaf surface that regulate gas exchange (CO2 in, O2 out) and water vapor loss.

• Production: Photosynthesis produces glucose (C6H12O6) and oxygen (O2).

• Splitting of Water: Water is split during the light reactions, releasing electrons, protons, and oxygen.

• Photosystems: Photosystem I and II are complexes in the thylakoid membrane that absorb light and drive electron transport. Photosystem II splits water; Photosystem I helps produce NADPH.

• Light Reaction: Occurs in the thylakoid membranes; converts light energy to chemical energy (ATP and NADPH).

• Calvin Cycle: Occurs in the stroma; uses ATP and NADPH to fix CO2 into glucose.

• CO2 Entry: CO2 enters the leaf through stomata and is fixed in the Calvin cycle.

• C3 vs. C4 vs. CAM Pathways: Different mechanisms for carbon fixation to adapt to environmental conditions.

• Energy Source: Sunlight is the ultimate energy source for most living things.

Equation for Photosynthesis:

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

• Types of Energy: Kinetic, potential, chemical, thermal, etc.

• Thermodynamics: The study of energy transformations; first law states energy cannot be created or destroyed.

• Electron Carriers: Molecules like NADP+ and NADPH transport electrons during photosynthesis.

Chapter 12 and 13: Cell Cycle, Mitosis, Meiosis, and Chromosome Behavior

Cell Cycle and Chromosome Dynamics

The cell cycle is the series of events that cells go through as they grow and divide. It includes interphase (G1, S, G2) and mitotic phase (mitosis and cytokinesis).

• Stages of Cell Cycle: G1 (growth), S (DNA synthesis), G2 (preparation for division), M (mitosis).

• Sister Chromatids vs. Homologous Chromosomes: Sister chromatids are identical copies formed during DNA replication; homologous chromosomes are pairs with the same genes but possibly different alleles.

• M Phase: Includes mitosis (nuclear division) and cytokinesis (cytoplasm division).

• Chromosome Behavior: Chromosomes condense, align, and separate during mitosis and meiosis.

• Mitosis vs. Meiosis: Mitosis produces two identical diploid cells; meiosis produces four genetically unique haploid cells.

• Haploid vs. Diploid: Haploid cells (n) have one set of chromosomes; diploid cells (2n) have two sets.

• Independent Assortment: Chromosomes are randomly distributed to gametes during meiosis, increasing genetic diversity.

• Resegregation: Occurs during meiosis when homologous chromosomes separate.

Chapter 14: Mendelian Genetics and Inheritance

Genotype, Phenotype, and Patterns of Inheritance

Mendelian genetics explains how traits are inherited through discrete units called genes. The genotype is the genetic makeup; the phenotype is the observable trait.

• Genotype vs. Phenotype: Genotype refers to the alleles present; phenotype is the physical expression.

• Homozygous vs. Heterozygous: Homozygous individuals have two identical alleles; heterozygous have two different alleles.

• Trait Inheritance: Traits are passed from parents to offspring through genes.

• Dominant vs. Recessive: Dominant alleles mask recessive alleles in heterozygotes.

• Mendelian Ratios: Typical monohybrid cross yields a 3:1 ratio in F2 generation.

• Non-Mendelian Genetics: Includes incomplete dominance, codominance, and polygenic inheritance.

• X-linked Disorders: Disorders associated with genes on the X chromosome, such as hemophilia.

• Carriers: Individuals who carry one copy of a recessive allele but do not express the trait.

• Punnett Squares: Used to predict the probability of offspring genotypes and phenotypes.

Chapter 15: Sex Determination, Linkage, and Chromosomal Alterations

Sex Chromosomes, Linkage, and Genetic Disorders

Sex determination is controlled by sex chromosomes (X and Y). Linkage refers to genes located close together on the same chromosome, which tend to be inherited together.

• Sex Determination: The presence of Y chromosome determines male phenotype; XX is female, XY is male.

• X-linked Traits: Traits determined by genes on the X chromosome; males are more susceptible to X-linked disorders.

• Linkage Map: Shows the relative positions of genes on a chromosome.

• Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to aneuploidy (e.g., Down syndrome).

• Chromosomal Alterations: Include deletion, inversion, duplication, and translocation.

• Genomic Imprinting: Differential expression of a gene depending on parent of origin.

Sample Table: Comparison of Mitosis and Meiosis

Feature	Mitosis	Meiosis
Number of Divisions	1	2
Number of Daughter Cells	2	4
Genetic Composition	Identical to parent	Genetically unique
Chromosome Number	Diploid (2n)	Haploid (n)
Function	Growth, repair	Sexual reproduction

Additional info:

• Polyploidy refers to cells with more than two sets of chromosomes, common in plants.

• Imprinting disorders can lead to diseases such as Prader-Willi and Angelman syndromes.