Genetics Fundamentals

Genetics

Key Concepts

• DNA (Deoxyribonucleic acid): a molecule that contains the genetic instructions used in the development and function of all living organisms
• Genes: segments of DNA that code for a specific trait or function
• Genotype: the complete set of genes an individual possesses
• Phenotype: the physical and behavioral characteristics of an individual resulting from the interaction of their genotype and the environment

DNA Structure

• Double Helix Model: DNA is composed of two complementary strands twisted together
• Nucleotides: building blocks of DNA, consisting of a sugar molecule, a phosphate group, and one of four nitrogenous bases (A, C, G, and T)
• Base Pairing: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C)

Genetic Inheritance

• Mendel's Laws:
  • Law of Segregation: each pair of alleles separates from each other during gamete formation
  • Law of Independent Assortment: alleles for different genes are sorted independently during gamete formation
• Dominant and Recessive Traits: dominant alleles will be expressed if an individual has one dominant and one recessive allele, while recessive alleles will only be expressed if an individual has two recessive alleles
• Incomplete Dominance: one allele is not completely dominant over the other, resulting in a combination of the two traits
• Polygenic Inheritance: multiple genes contribute to a single trait

Genetic Variation

• Mutations: changes in the DNA sequence, can be spontaneous or induced
• Genetic Drift: random events that alter the frequency of alleles in a population
• Gene Flow: movement of alleles from one population to another
• Genetic Recombination: exchange of genetic material between homologous chromosomes during meiosis, increasing genetic variation