Mendelian Genetics: Key Terms & Punnett Squares

Chapter 10: Mendelian Genetics

• Gregor Mendel is known as the "Father of Genetics."
• Mendel studied pea plants.
• He discovered inheritance patterns and formulated the law of segregation and the law of independent assortment.

Law of Segregation

• During meiosis, alleles for a gene separate, so each gamete gets only one allele.

Key Vocabulary

• Homozygous dominant: Two dominant alleles (e.g., AA).
• Homozygous recessive: Two recessive alleles (aa).
• Heterozygous: One dominant and one recessive allele (Aa).
• Genotype: Genetic makeup (e.g., Aa, aa).
• Phenotype: Observable trait (e.g., purple flowers, tall plant).
• Homologous chromosomes: Pairs of chromosomes, one from each parent.
• Tetrad: Pair of homologous chromosomes (4 chromatids) formed during prophase I of meiosis.

Punnett Squares

• Monohybrid cross: Involves 1 gene with 2 alleles (Aa x Aa)
• Dihybrid cross: Involves 2 genes with 4 alleles (AaBb x AaBb)

Blood Types

• Type A: Genotypes AA or AO; has A antigens and anti-B antibodies.
• Type B: Genotypes BB or BO; has B antigens and anti-A antibodies.
• Type AB: Genotype AB; has both A and B antigens; no antibodies (universal recipient).
• Type O: Genotype OO; has no antigens; both anti-A and anti-B antibodies (universal donor).

Genetic Terms

• Linked genes: Genes located on the same chromosome, inherited together.
• Crossing over: Determines gene distance; the more often two genes are separated by crossing over, the further they are apart.
• Incomplete dominance: Blending of traits (e.g., red + white = pink).
• Codominance: Both traits are fully expressed (e.g., AB blood type).
• Pleiotropy: One gene affects multiple traits.
• Polygenic traits: Many genes contribute to one trait (e.g., skin color).
• Multiallelic traits: More than two alleles exist (e.g., blood type).
• Sex-linked traits: Traits on the X chromosome (e.g., color blindness).

Chapter 12: Microevolution

Darwin's Journey

• Traveled on the HMS Beagle.
• Visited the Galápagos Islands.
• Darwin observed finches with different beaks and tortoises with different shells.

Influences on Darwin

• Charles Lyell: Proposed that Earth changes over time (geology).
• Thomas Malthus: Discussed overpopulation and competition.
• Artificial selection: Practiced by farmers/breeders.

Evidence for Evolution

• Fossils, comparative anatomy, embryology, and DNA/molecular biology.

Key Terms

• Homology: Similar structures due to shared ancestry.
• Vestigial structures: Structures no longer used (e.g., human tailbone).
• Population: Unit of evolution.
• Genetic variation: Caused by mutation, meiosis, and sexual reproduction.
• Polymorphism: Multiple forms of traits in a population.

Mechanisms of Evolution

• Mutation: Source of new alleles.
• Gene flow: Migration in/out of a population.
• Genetic drift: Random changes in small populations (e.g., bottleneck, founder effect).
• Natural selection: Differential survival and reproduction.
• Sexual selection: Traits that increase mating success.

Chapter 14: Macroevolution

• Speciation

Defining Species

• Biological species concept: Interbreed and produce fertile offspring.

Reproductive Barriers

• Prezygotic: Prevent mating or fertilization (e.g., timing, behavior, habitat).
• Postzygotic: Hybrid offspring don't survive or are sterile.

Types of Speciation

• Allopatric: Physical barrier separates populations.
• Sympatric: New species without physical separation (e.g., polyploidy in plants).

Other Concepts

• Adaptive radiation: One species evolves into many (e.g., Darwin's finches).
• Tempo of speciation: Gradual vs. punctuated equilibrium.

Chapter 21: Animals and Animal Evolution

General Animal Characteristics

• Multicellular, heterotrophic, no cell walls.
• Sexual reproduction with diploid-dominant life cycle.
• Early development: Zygote → Blastula → Gastrula.

Developmental Terms

• Blastula: Hollow ball of cells.
• Gastrulation: Formation of three germ layers.
• Protostomes: Mouth forms first (e.g., mollusks, arthropods).
• Deuterostomes: Anus forms first (e.g., chordates, echinoderms).

Animal Phylogeny Branching Points

1. True tissues?
2. Symmetry (radial vs. bilateral)
3. Body cavity (acoelomate, pseudocoelomate, coelomate)
4. Protostome or deuterostome?

Animal Phyla (with examples)

• Porifera: Sponges – no true tissues, filter feeders.
• Cnidaria: Jellyfish, coral – radial symmetry, stinging cells.
• Platyhelminthes: Flatworms – acoelomate, simple organs.
• Nematoda: Roundworms – pseudocoelom, complete digestive tract.
• Annelida: Earthworms – segmented body.
• Mollusca: Snails, clams, squids – soft body, many with shells.
• Arthropoda: Insects, spiders, crustaceans – exoskeleton, jointed legs.
• Echinodermata: Starfish – radial adults, bilateral larvae, deuterostomes.
• Chordata: Vertebrates (fish, amphibians, reptiles, birds, mammals) – notochord, dorsal nerve cord.