AP Biology Virtual Lab: Meiosis, Genetic Diversity & Nondisjunction

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Lab Goal: By the end of this activity, you should be able to explain how meiosis produces genetically different haploid gametes and how errors in chromosome separation can affect offspring.

Lab Progress

Stage 1 of 7: Background and Prediction

Stage 1: Background and Prediction

Meiosis is a specialized cell division process that produces haploid gametes from a diploid parent cell. It supports sexual reproduction by reducing chromosome number and increasing genetic variation.

AP Biology Unit 5 Meiosis Genetic Diversity

Prediction: If crossing over and independent assortment did not occur, how would offspring be affected?

Check for Understanding

Which statement best explains the main purpose of meiosis?

A. To produce genetically identical diploid body cells B. To produce haploid gametes and increase genetic variation C. To repair damaged tissues through repeated cell division D. To copy DNA without changing chromosome number

Stage 2: Model the Diploid Parent Cell

This cell begins with two homologous chromosome pairs. Each pair includes one maternal chromosome and one paternal chromosome.

Observation: What does it mean for this parent cell to be diploid?

Interactive Decision

What must happen before meiosis begins?

A. DNA must replicate during interphase B. Homologous chromosomes must separate before DNA replication C. The cell must immediately divide into four cells D. Chromosome number must double permanently

Stage 3: Crossing Over in Prophase I

During Prophase I, homologous chromosomes pair and exchange DNA segments. This produces recombinant chromosomes.

Explain how crossing over contributes to genetic variation.

AP-Style Question

Which event directly causes recombinant chromatids?

A. Separation of sister chromatids during Meiosis II B. Exchange of DNA between homologous chromosomes C. Replication of DNA during interphase D. Cytokinesis after Telophase II

Stage 4: Independent Assortment in Metaphase I

Homologous chromosome pairs line up randomly at the metaphase plate. This random orientation creates different possible chromosome combinations in gametes.

Explain why independent assortment increases genetic variation.

Quantitative Reasoning

If a species has a haploid number of 6, how many possible chromosome combinations can independent assortment produce?

A. 6 B. 12 C. 64 D. 128

Stage 5: Meiosis I and Meiosis II

In Meiosis I, homologous chromosomes separate. In Meiosis II, sister chromatids separate. The final result is four haploid gametes.

Observation: Why are the gametes genetically different from each other?

Check for Understanding

Which statement correctly compares Meiosis I and Meiosis II?

A. Meiosis I separates homologous chromosomes; Meiosis II separates sister chromatids B. Meiosis I separates sister chromatids; Meiosis II separates homologous chromosomes C. Both divisions separate homologous chromosomes D. Both divisions produce diploid cells

Stage 6: Nondisjunction Investigation

Nondisjunction occurs when chromosomes fail to separate properly. This can produce gametes with too many or too few chromosomes.

Explain why nondisjunction can cause abnormal chromosome numbers in offspring.

AP-Style Application

Why does nondisjunction in Meiosis I usually affect more gametes than nondisjunction in Meiosis II?

A. Because all homologous chromosomes fail to replicate B. Because the error occurs before both final divisions are completed C. Because cytokinesis stops completely D. Because gametes become diploid every time

Stage 7: Final AP Biology Discussion

Respond using complete scientific explanations. Your answers should use evidence from the simulation.

1. How does meiosis maintain chromosome continuity across generations? 2. Explain how crossing over and independent assortment differ from each other. 3. A diploid organism has 10 chromosomes. Predict the haploid number and explain your reasoning. 4. Explain how nondisjunction may affect phenotype after fertilization. 5. Construct an argument explaining why sexual reproduction increases variation in a population.