General Biology Study Notes: Scientific Method, Genetics, Meiosis, and DNA

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Science is a systematic approach to understanding the natural world through observation, experimentation, and evidence-based reasoning.

Scientific Method: A logical process used to investigate questions and test hypotheses.
Hypotheses: Proposed explanations for observations, which can be tested experimentally.
Null Hypothesis (H0): States there is no effect or difference.
Alternative Hypothesis (Ha): States there is an effect or difference.
Predictions: Specific outcomes expected if the hypothesis is correct.

Example: The giraffe study investigates whether neck length affects feeding success.

Data Analysis: Involves variables, data points, and statistical significance to interpret results.
Graph/Data Interpretation: Visual representation of data to identify trends and relationships.

Gregor Mendel’s experiments with pea plants established the foundational principles of genetics.

Example: Crossing pea plants with different flower colors to predict offspring ratios.

Principle of Segregation: Each individual has two alleles for each gene, which separate during gamete formation.
Principle of Independent Assortment: Genes for different traits assort independently during gamete formation.

Meiosis is a type of cell division that reduces the chromosome number by half, producing haploid gametes (sperm and egg cells).

Stages of Meiosis: Includes Meiosis I (separates homologous chromosomes) and Meiosis II (separates sister chromatids).
Haploid: Cells with one set of chromosomes (n).
Diploid: Cells with two sets of chromosomes (2n).

Life Cycle: Sequence of stages in the life of an organism, including meiosis and fertilization.
Meiosis in Life Cycle: Produces gametes in animals; spores in plants and fungi.

Principle of Segregation: Homologous chromosomes separate so each gamete receives one allele of each gene.
Principle of Independent Assortment: Chromosomes assort independently, increasing genetic variation.

Example: Meiosis explains why siblings have different genetic combinations.

DNA (deoxyribonucleic acid) is the molecule that stores genetic information in all living organisms.

Nucleotide Components: Each nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, guanine).
Double Helix: DNA is composed of two strands forming a double helix.

Genotype: The genetic code in DNA.
Phenotype: The physical expression of the genotype as traits.
Mutation: A change in the DNA sequence that can alter genotype and potentially phenotype.

Example: A mutation in the gene for hemoglobin can cause sickle cell anemia.

Concept	Definition	Example
Gene	Unit of heredity encoding a trait	Gene for flower color in peas
Allele	Alternative form of a gene	Allele for purple or white flowers
Genotype	Genetic makeup of an organism	PP, Pp, or pp for flower color
Phenotype	Observable trait	Purple or white flowers
Mutation	Change in DNA sequence	Sickle cell mutation
Central Dogma	Flow of genetic information	DNA → mRNA → Protein