ap bio unit 5 cheat sheet

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01-02-2025

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This cheat sheet summarizes key concepts for AP Biology Unit 5, focusing on inheritance patterns, molecular genetics, and evolution. Remember that this is a supplement to your textbook and class notes – it's designed to highlight key information and aid in memorization, not replace thorough study.

I. Mendelian Genetics & Inheritance Patterns

• Basic Principles: Understand Mendel's Laws of Segregation and Independent Assortment. Know the difference between genotype (genetic makeup) and phenotype (observable traits).
• Punnett Squares: Master creating and interpreting Punnett squares to predict offspring genotypes and phenotypes for monohybrid (one gene) and dihybrid (two genes) crosses. Practice problems with different dominance patterns.
• Non-Mendelian Inheritance: Be prepared for questions on:
  • Incomplete Dominance: Heterozygotes show a blended phenotype (e.g., pink flowers from red and white parents).
  • Codominance: Both alleles are fully expressed in heterozygotes (e.g., AB blood type).
  • Multiple Alleles: More than two alleles exist for a gene (e.g., ABO blood group system).
  • Pleiotropy: One gene affects multiple phenotypic traits.
  • Epistasis: One gene's expression masks or modifies the expression of another gene.
  • Polygenic Inheritance: Multiple genes contribute to a single phenotypic trait (e.g., human height, skin color).
  • Sex-linked Traits: Genes located on sex chromosomes (X or Y). Understand X-linked recessive inheritance patterns (more common in males).

II. Molecular Genetics

• DNA Structure & Replication: Know the components of DNA (nucleotides, sugar-phosphate backbone, base pairing), the process of DNA replication (semi-conservative), and the role of enzymes (helicase, polymerase, ligase).
• Transcription & Translation: Understand the central dogma (DNA → RNA → protein). Know the steps of transcription (creating mRNA from DNA) and translation (synthesizing a polypeptide from mRNA using ribosomes and tRNA). Be familiar with the genetic code (codon chart).
• Gene Regulation: Learn about mechanisms that control gene expression, including:
  • Operons (Prokaryotes): Understand the lac operon as an example of inducible gene regulation.
  • Eukaryotic Gene Regulation: Know the role of transcription factors, enhancers, silencers, and epigenetic modifications (DNA methylation, histone modification).
• Mutations: Understand different types of mutations (point mutations: substitution, insertion, deletion; chromosomal mutations: deletion, duplication, inversion, translocation) and their potential effects on protein function.

III. Evolutionary Genetics

• Hardy-Weinberg Equilibrium: Know the conditions required for Hardy-Weinberg equilibrium (no mutation, random mating, no gene flow, large population size, no natural selection). Be able to use the Hardy-Weinberg equations (p + q = 1; p² + 2pq + q² = 1) to calculate allele and genotype frequencies.
• Mechanisms of Evolution: Understand how each mechanism alters allele frequencies:
  • Mutation: Introduces new alleles.
  • Gene Flow: Movement of alleles between populations.
  • Genetic Drift: Random changes in allele frequencies (bottleneck effect, founder effect).
  • Natural Selection: Differential survival and reproduction based on advantageous traits. Know the different types of selection (directional, stabilizing, disruptive).
• Speciation: Understand the different modes of speciation (allopatric, sympatric).
• Phylogenetic Trees: Be able to interpret phylogenetic trees to understand evolutionary relationships between species.

IV. Practice & Resources

This cheat sheet is a starting point. Thoroughly review your textbook, class notes, and practice problems. Consider using practice tests and flashcards to reinforce your understanding of the concepts. Remember to focus on understanding the underlying principles rather than just memorizing facts. Good luck!