šŸ“‹ Exam Overview & Structure

Exam Format

The AP Biology II Mid-Year Exam consists of two main sections:

  • Section A: 40 Multiple Choice Questions (75 minutes)
  • Section B: 2 Free Response Questions (45 minutes)

IMPORTANT VIDEOS

  • 6.3: Daily Video 1 ā€“ Watch
  • 6.3: Daily Video 2 ā€“ Watch
  • 6.4: Daily Video 1 ā€“ Watch
  • 6.4: Daily Video 2 ā€“ Watch
  • 6.5: Daily Video 1 ā€“ Watch
  • 6.5: Daily Video 2 ā€“ Watch
  • 6.6: Daily Video 1 ā€“ Watch
  • 6.7: Daily Video 1 ā€“ Watch
  • 6.7: Daily Video 2 ā€“ Watch
  • 6.7: Daily Video 3 ā€“ Watch

Key Topic Distribution

Topic Area Approximate % of MC Key Concepts
Genetics & Inheritance 30% Mendelian genetics, probability, pedigrees
Molecular Biology 25% DNA replication, protein synthesis, biotechnology
Gene Regulation 20% Operons, transcription factors, mutations
Evolution & Populations 15% Hardy-Weinberg, natural selection, genetic drift
Experimental Design 10% Data analysis, graph interpretation, controls

Free Response Question Types

FRQs typically assess your ability to:

  1. Analyze data from experiments or observations
  2. Explain biological concepts in context
  3. Perform calculations (probability, frequencies)
  4. Construct graphs with proper labeling
  5. Make predictions based on evidence

šŸ§¬ Mendelian Genetics & Probability

Core Concepts

Mendelian genetics explains how traits are inherited from parents to offspring through the transmission of genes.

Key Principles:

  • Law of Segregation: Alleles separate during gamete formation
  • Law of Independent Assortment: Genes on different chromosomes assort independently
  • Dominance/Recessiveness: Dominant alleles mask recessive ones

Probability Rules for Genetics

Cross Type Genotype Ratio (F2) Phenotype Ratio (F2)
Monohybrid (Aa Ɨ Aa) 1:2:1 (AA:Aa:aa) 3:1 (Dominant:Recessive)
Dihybrid (AaBb Ɨ AaBb) 9 different genotypes 9:3:3:1
Test Cross (Aa Ɨ aa) 1:1 (Aa:aa) 1:1

Probability Calculations:

For independent events: Multiply probabilities
For mutually exclusive events: Add probabilities

Question: A couple has 5 sons. What is the probability their next child will be a son?
Answer: 1/2 or 50%. Each reproductive event is independent. The sex of previous children does not affect future probabilities.
Question: In a dihybrid cross (AaBb Ɨ AaBb), what is the probability of offspring with genotype aabb?
Answer: 1/16. Probability of aa = 1/4, probability of bb = 1/4. Multiply: (1/4) Ɨ (1/4) = 1/16.

Chi-Square Test for Goodness of Fit

Used to determine if observed data matches expected ratios:

Formula: Ļ‡Ā² = Ī£[(O - E)Ā²/E]

Degrees of freedom: n - 1 (where n = number of categories)

Significance: p < 0.05 indicates significant difference from expected

šŸ”¬ Molecular Genetics

Central Dogma of Molecular Biology

DNA ā†’ RNA ā†’ Protein

Key Processes:

  • Replication: DNA ā†’ DNA (semiconservative)
  • Transcription: DNA ā†’ RNA (mRNA, tRNA, rRNA)
  • Translation: RNA ā†’ Protein (at ribosomes)

Enzyme Reference Table

Enzyme Function Key Feature
DNA polymerase Adds nucleotides during DNA replication 5'ā†’3' synthesis; 3'ā†’5' proofreading
DNA ligase Joins Okazaki fragments Seals nicks in DNA backbone
RNA polymerase Synthesizes RNA from DNA template Doesn't need primer; binds promoter
Reverse transcriptase Makes DNA from RNA template Found in retroviruses (HIV)
Restriction enzyme Cuts DNA at specific sequences Used in DNA cloning
Question: What was the key finding of the Avery-MacLeod-McCarty experiment?
Answer: DNA is the genetic material. When DNA was destroyed, transformation did not occur, but destroying proteins did not prevent transformation.
Question: How does DNA differ from RNA in structure?
Answer:
  • DNA: double-stranded, deoxyribose sugar, thymine base
  • RNA: single-stranded, ribose sugar, uracil base

Biotechnology Applications

PCR (Polymerase Chain Reaction):

  • Amplifies specific DNA sequences
  • Requires: DNA template, primers, Taq polymerase, dNTPs
  • Cycles: Denaturation ā†’ Annealing ā†’ Extension

Gel Electrophoresis:

  • Separates DNA fragments by size
  • Smaller fragments migrate faster/farther
  • Used in DNA fingerprinting, PCR analysis

āš™ļø Gene Regulation

The Lac Operon (Inducible System)

Regulates lactose metabolism in E. coli.

Key Components:

  • lacI: Repressor gene (always expressed)
  • Operator: Repressor binding site
  • Promoter: RNA polymerase binding site
  • lacZ: Ī²-galactosidase (breaks down lactose)
  • lacY: Permease (transports lactose)

Lac Operon Regulation

Condition Repressor CAP/cAMP Transcription
Lactose -, Glucose + Bound to operator Inactive OFF
Lactose +, Glucose + Not bound (lactose present) Inactive LOW
Lactose +, Glucose - Not bound Active (cAMP high) HIGH

Maximal transcription requires: Lactose present AND glucose absent

Question: What happens if the operator has a mutation preventing repressor binding?
Answer: Constitutive expression. The lac operon would be transcribed even without lactose present.
Question: How do enhancers regulate gene expression in eukaryotes?
Answer: Enhancers are DNA sequences that bind activator proteins. These activators interact with the transcription initiation complex to increase transcription rates. Enhancers can be located far from the gene they regulate.

Types of Mutations

Mutation Type Description Effect on Protein
Silent Base change but same amino acid None
Missense Different amino acid Variable (mild to severe)
Nonsense Creates stop codon Truncated protein
Frameshift Insertion/deletion of bases (not multiple of 3) Complete change after mutation

šŸ¦‹ Evolution & Population Genetics

Hardy-Weinberg Equilibrium

Describes a non-evolving population:

Conditions:

  • No mutations
  • No gene flow (migration)
  • Large population size
  • Random mating
  • No natural selection

Equations:

p + q = 1 (allele frequencies)
pĀ² + 2pq + qĀ² = 1 (genotype frequencies)

Where:
p = frequency of dominant allele
q = frequency of recessive allele
pĀ² = frequency of homozygous dominant
2pq = frequency of heterozygous
qĀ² = frequency of homozygous recessive

Types of Natural Selection

Type Description Example
Directional Favors one extreme phenotype Larger beak size during drought
Stabilizing Favors intermediate phenotype Human birth weight
Disruptive Favors both extremes Black and white moths, not gray
Question: In a population, 16% show the recessive phenotype. What is the frequency of the recessive allele?
Answer: qĀ² = 0.16, so q = āˆš0.16 = 0.4. The recessive allele frequency is 40%.
Question: What is heterozygote advantage? Give an example.
Answer: Heterozygotes have higher fitness than either homozygote. Example: Sickle cell trait (HbA/HbS) provides resistance to malaria while HbA/HbA are susceptible and HbS/HbS have sickle cell disease.

Hox Genes & Evolutionary Development

Hox genes control body segmentation and are highly conserved across animals.

Key Concepts:

  • Regulate development of body structures
  • Changes in regulation (timing, location) lead to morphological differences
  • Example: Different neck lengths in birds vs. mammals

All mammals have 7 cervical vertebrae, while birds have varying numbers.

āœļø FRQ Examples & Strategies

FRQ Scoring Guidelines

Free Response Questions are scored on a scale, typically with these criteria:

  1. Scientific understanding (correct concepts)
  2. Application of knowledge to new situations
  3. Data analysis and interpretation
  4. Communication (clear, organized writing)

Common Point Deductions:

  • Not answering all parts of the question
  • Vague answers without specific evidence
  • Incorrect terminology
  • Missing units in calculations

Sample FRQ: Genetics Problem

In pea plants, purple flowers (P) are dominant to white (p), and tall stems (T) are dominant to short (t). A dihybrid cross (PpTt Ɨ PpTt) produces 640 offspring.

Data:

  • Purple, tall: 360
  • Purple, short: 120
  • White, tall: 120
  • White, short: 40

How to approach:

  1. Calculate expected ratio: 9:3:3:1 for independent assortment
  2. Compare observed to expected: Use chi-square test if asked
  3. Interpret results: If significant difference, genes may be linked
  4. Calculate recombination frequency if genes are linked
Question: What should you always do before starting to write an FRQ response?
Answer: Read the entire question carefully and underline key terms and instructions. Make sure you understand what each part is asking before you begin writing.
Question: How should you structure your response for an FRQ that asks you to "describe" and "explain"?
Answer: First clearly describe the phenomenon or data, then provide a biological explanation. Use specific terminology and connect your explanation to the data provided in the question.

FRQ Writing Template

Use this structure for most FRQ responses:

  1. Restate the question in your opening sentence
  2. Provide specific evidence from data/graphs
  3. Use correct terminology (define if necessary)
  4. Explain "why" - don't just describe
  5. Connect to broader concepts when appropriate
  6. Conclude clearly with your answer to the question

šŸ“š Practice Questions

Interactive Flashcards

Click on any flashcard to reveal the answer. Test yourself on key concepts!

DNA replication is described as semiconservative. What does this mean?
Answer: Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.
What is the difference between mitosis and meiosis in terms of genetic variation?
Answer: Mitosis produces genetically identical daughter cells (clones). Meiosis produces genetically unique gametes through independent assortment and crossing over.
Explain how the lac operon is regulated when both lactose and glucose are present.
Answer: Lactose binds to the repressor, inactivating it so it doesn't bind the operator. However, glucose is present, so cAMP levels are low and CAP is inactive. Transcription occurs at a low level.
A population is in Hardy-Weinberg equilibrium. The frequency of the recessive allele is 0.3. What percentage of the population is heterozygous?
Answer: q = 0.3, so p = 0.7. Heterozygous frequency = 2pq = 2(0.7)(0.3) = 0.42 or 42%.
What type of mutation changes a codon from UGU (cysteine) to UGA (stop)?
Answer: Nonsense mutation. It creates a premature stop codon, resulting in a truncated protein.

Calculation Practice

Problem: In a dihybrid cross between two heterozygous plants (RrYy Ɨ RrYy), what is the probability of offspring with round seeds and yellow color if R (round) and Y (yellow) are dominant?

Data Interpretation Practice

Scenario: Gel electrophoresis results show three bands for a DNA sample. Band 1 is at 500 bp, Band 2 at 1000 bp, Band 3 at 1500 bp.

Question: Which band represents the largest DNA fragment?

šŸŽÆ Study Strategies

Effective Study Methods

Active Recall (Most Effective):

  • Test yourself without looking at notes
  • Use flashcards (like the ones in this guide!)
  • Explain concepts aloud as if teaching someone
  • Practice with past exam questions

Spaced Repetition:

  • Review material multiple times over days/weeks
  • Focus more on difficult concepts
  • Use a study schedule to space out topics

Interleaving:

  • Mix different topics in a study session
  • Instead of "genetics only" sessions, mix genetics, molecular bio, and evolution
  • Helps with making connections between concepts

Week-Before-Exam Study Plan

Days Before Focus Activities
7-5 Content Review Review all major topics; create summary sheets
4-3 Practice Exams Complete full practice tests under timed conditions
2 Weak Areas Focus on challenging topics; review mistakes
1 Light Review Review diagrams and formulas only; no new material
0 Exam Day Eat well, arrive early, stay calm
Question: What should you do if you encounter a multiple-choice question you don't know?
Answer: 1) Eliminate obviously wrong answers. 2) Make an educated guess. 3) Mark it and return if time permits. Never leave questions blank on most exams.
Question: How can you prevent careless mistakes on calculations?
Answer: 1) Write out all steps. 2) Include units in calculations. 3) Check your work by estimating. 4) Verify your answer makes biological sense.

Common Mistakes to Avoid

  • Confusing terminology: Transcription vs. translation; genotype vs. phenotype
  • Forgetting units: Map units = % recombination; centimorgan = 1 map unit
  • Misreading questions: Watch for "NOT" or "EXCEPT" in questions
  • Rushing through FRQs: Read all parts before starting to write
  • Not showing work: Always show calculations for partial credit

Final Preparation Checklist