Genetics Study Guide PDF

Genetics Study Guide Mendel’s Experiments ​ Purpose: Studied inheritance of traits in pea plants. ​ F1 Generation: 100% tall plants (dominant trait). ​ F2 Generation: 75% tall, 25% short (3:1 ratio). ​ Key Concept: The tall allele (T) is dominant over the short allele (t)....

Genetics Study Guide Mendel’s Experiments ​ Purpose: Studied inheritance of traits in pea plants. ​ F1 Generation: 100% tall plants (dominant trait). ​ F2 Generation: 75% tall, 25% short (3:1 ratio). ​ Key Concept: The tall allele (T) is dominant over the short allele (t). Punnett Squares & Probability ​ Purpose: Used to predict genotype and phenotype ratios. ​ Key Terms: ○​ Dominant allele (A): Masks the effect of a recessive allele. ○​ Recessive allele (a): Only expressed when two copies are present. ○​ Homozygous (AA or aa): Two identical alleles. ○​ Heterozygous (Aa): One dominant and one recessive allele. ○​ Genotype: Genetic makeup (e.g., Aa, AA, aa). ○​ Phenotype: Physical traits (e.g., brown eyes, short hair). ​ Monohybrid Cross: Involves a single trait (e.g., eye color). ​ Dihybrid Cross: Involves two traits (e.g., eye color and hair type). ○​ Phenotypic ratio for AaBb × AaBb: 9:3:3:1. ○​ Codominance: Both alleles are fully expressed (e.g., black and white speckled chicken). ○​ Incomplete Dominance: Heterozygous phenotype is a blend of both alleles (e.g., pink flowers from red and white parents). Example Question: ​ A cross between a homozygous black rabbit (BB) and a homozygous white rabbit (ww) produces all heterozygous gray rabbits. This demonstrates incomplete dominance. Meiosis vs. Mitosis ​ Mitosis: ○​ Purpose: Growth, repair, asexual reproduction. ○​ Key Features: One division, results in 2 identical daughter cells, maintains chromosome number (diploid). ○​ Phases: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis. ​ Meiosis: ○​ Purpose: Sexual reproduction, genetic variation. ○​ Key Features: Two divisions, results in 4 genetically unique gametes (haploid). ○​ Key Phases: ​ Meiosis I: Prophase I (crossing over), Metaphase I, Anaphase I, Telophase I (results in two haploid cells). ​ Meiosis II: Similar to mitosis, but without chromosome replication. ○​ Crossing over: Increases genetic variation. ○​ Independent assortment: Ensures unique genetic combinations. ○​ Chromosome number: Reduces from 46 (diploid) to 23 (haploid). Genetics Terminology ​ Phenotype: Observable traits (e.g., eye color). ​ Genotype: Genetic composition (e.g., BB, Bb, bb). ​ Homozygous: Identical alleles (BB or bb). ​ Heterozygous: Different alleles (Bb). ​ Sex-Linked Traits: Traits carried on X and Y chromosomes. ​ Mutation: Permanent changes in DNA, which can be harmful, neutral, or beneficial. Genetic Disorders & Pedigrees ​ Sickle Cell Anemia: Abnormally shaped red blood cells (recessive). ​ Cystic Fibrosis: Thick mucus in lungs & intestines (recessive). ​ Hemophilia: Blood does not clot properly (sex-linked). ​ Huntington’s Disease: Dominant disorder causing nerve degeneration. ​ Pedigrees: ○​ Used to trace inheritance of traits through generations. ○​ Carriers: Individuals with one recessive allele but do not show the trait. Human Genome & Genetic Engineering ​ Human Genome Project: Mapped all human genes. ​ Selective Breeding: Choosing organisms with desired traits. ​ Cloning: Creating genetically identical organisms. ​ Genetic Engineering: Altering DNA for medical and agricultural purposes. ​ CRISPR: Gene-editing technology to make precise changes in DNA. Genetic Disorders Review ​ Autosomal Dominant: Trait appears in every generation. ​ Autosomal Recessive: Trait can skip generations. ​ X-linked Traits: More common in males due to having only one X chromosome. Cancer ​ Cause: Uncontrolled cell growth due to mutations. ​ Tumors: ○​ Benign: Non-cancerous, does not spread. ○​ Malignant: Cancerous, spreads to other tissues. ​ Treatment: Surgery, chemotherapy, radiation.