Genetics Final Exam Study Guide: Developmental and Population Genetics

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Q1. What are four major cellular events that occur during development of the organism? Which of these occurs in animals but not in plants?

Background

Topic: Developmental Genetics

This question tests your understanding of the fundamental cellular processes that drive the development of multicellular organisms, and asks you to distinguish between processes in animals and plants.

Key Terms:

Cell division
Cell differentiation
Cell migration
Cell death (apoptosis)
Cell expansion (especially in plants)

Step-by-Step Guidance

List the four major cellular events that are commonly involved in the development of multicellular organisms. Consider processes such as cell division, differentiation, migration, and programmed cell death.
For each event, briefly define what it means in the context of development.
Think about which of these processes are universal to both plants and animals, and which are unique to animals (for example, consider whether plant cells migrate).
Identify the event that occurs in animals but not in plants, and explain why this difference exists based on cellular structure (e.g., cell walls in plants).

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Q2. What is the difference between a totipotent and a pluripotent cell? Give an example of each.

Background

Topic: Stem Cell Potency

This question is about the different capacities of cells to develop into various cell types during development.

Key Terms:

Totipotent: Can give rise to all cell types, including extraembryonic tissues.
Pluripotent: Can give rise to all cell types of the body, but not extraembryonic tissues.

Step-by-Step Guidance

Define what is meant by 'totipotent' and 'pluripotent' in the context of developmental biology.
Think of an example of a totipotent cell (hint: consider the earliest stages after fertilization).
Think of an example of a pluripotent cell (hint: consider cells from the inner cell mass of the blastocyst).
Summarize the main difference between these two types of cells in terms of their developmental potential.

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Q3. In the development of bilateral animals, what are the three major body-plan axes?

Background

Topic: Body Plan Organization

This question tests your knowledge of the spatial organization of animal bodies during development.

Key Terms:

Anterior-posterior axis
Dorsal-ventral axis
Left-right axis

Step-by-Step Guidance

Recall the three main axes that define the body plan of bilateral animals.
Define each axis and describe what body regions they correspond to.
Think about how these axes are established during early development.

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Q4. In Drosophila development, what is a key difference between the syncytial blastoderm and the cellular blastoderm? When during development does this change occur?

Background

Topic: Drosophila Embryogenesis

This question focuses on the early stages of fruit fly development and the transition from a multinucleate to a cellular embryo.

Key Terms:

Syncytium: A multinucleate cell formed by multiple nuclear divisions without cytokinesis.
Cellularization: The process by which cell membranes form around nuclei, creating individual cells.

Step-by-Step Guidance

Define what is meant by 'syncytial blastoderm' and 'cellular blastoderm' in Drosophila development.
Describe the main structural difference between these two stages.
Identify the developmental event that marks the transition from syncytial to cellular blastoderm.
Indicate approximately when (in terms of developmental timing or nuclear division cycles) this transition occurs.

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Q5. Describe the role of each major category of developmental genes in Drosophila development.

Background

Topic: Genetic Control of Development

This question is about the hierarchy of gene regulation that patterns the Drosophila embryo.

Key Terms:

Maternal effect genes
Gap genes
Pair-rule genes
Segment polarity genes
Homeotic genes

Step-by-Step Guidance

List the major categories of developmental genes in Drosophila (as above).
For each category, briefly describe its role in establishing the body plan.
Consider the order in which these genes act during development (from maternal effect to homeotic genes).
Think about how mutations in each category would affect embryonic patterning.

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Q6. Describe the result of loss-of-function mutations to each of the major categories of developmental genes in Drosophila development.

Background

Topic: Mutational Analysis in Development

This question asks you to predict the phenotypic consequences of disrupting different classes of developmental genes.

Key Terms:

Loss-of-function mutation
Maternal effect genes
Gap genes
Pair-rule genes
Segment polarity genes
Homeotic genes

Step-by-Step Guidance

For each gene category, recall its normal function in embryonic patterning.
Predict what would happen to the embryo if that gene category is nonfunctional (e.g., missing segments, altered segment identity).
Think about specific examples, such as bicoid mutants or homeotic transformations.
Summarize the general pattern of defects for each gene class.

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Q7. Why are bicoid and nanos genes categorized as maternal effect genes? What does ‘maternal effect’ mean?

Background

Topic: Maternal Effect Genes

This question is about how certain genes provided by the mother influence early embryonic development.

Key Terms:

Maternal effect gene
Bicoid
Nanos

Step-by-Step Guidance

Define what is meant by a 'maternal effect gene'.
Explain how the products of bicoid and nanos genes are supplied to the embryo.
Describe the consequences for the embryo if the mother lacks functional copies of these genes.
Summarize why these genes are classified as maternal effect genes.

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Q8. How does the distribution of bicoid protein in the early embryo affect the expression of the gap gene hunchback? Describe the role of bicoid protein at the molecular level. Is bicoid trans-acting or cis-acting? Are hunchback regulatory sites trans-acting or cis-acting?

Background

Topic: Gene Regulation in Development

This question explores how gradients of regulatory proteins control gene expression during early development.

Key Terms:

Bicoid protein
Gap gene (hunchback)
Trans-acting factor
Cis-acting regulatory element

Step-by-Step Guidance

Describe how the bicoid protein gradient is established in the embryo.
Explain how bicoid acts as a transcription factor to regulate hunchback expression.
Define what is meant by 'trans-acting' and 'cis-acting' in gene regulation.
Classify bicoid and hunchback regulatory sites as trans- or cis-acting, and explain your reasoning.

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Q9. What is the difference between the homeobox and the homeodomain? What role does the homeodomain play in regulating gene expression during development?

Background

Topic: Homeotic Genes and Protein Domains

This question is about the molecular features of homeotic genes and their protein products.

Key Terms:

Homeobox: A DNA sequence found in homeotic genes.
Homeodomain: The protein domain encoded by the homeobox, which binds DNA.

Step-by-Step Guidance

Define 'homeobox' and 'homeodomain' and explain how they are related.
Describe the function of the homeodomain in the context of gene regulation.
Explain why the homeodomain is important for developmental gene expression.

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Q10. What types of genes reside in the Antennapedia and bithorax clusters in the Drosophila genome? Which cluster is responsible for the development of anterior segments, and which is responsible for posterior segments?

Background

Topic: Hox Gene Clusters

This question focuses on the organization and function of homeotic gene clusters in fruit flies.

Key Terms:

Antennapedia complex
Bithorax complex
Hox genes
Anterior/posterior segments

Step-by-Step Guidance

Identify the types of genes found in the Antennapedia and bithorax clusters.
Describe the developmental roles of each cluster.
Determine which cluster specifies anterior versus posterior segment identity.

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Q11. How many clusters of Hox genes are carried in vertebrate animals? What process has led to this number?

Background

Topic: Hox Gene Evolution

This question is about the organization of Hox genes in vertebrates and the evolutionary processes that shaped them.

Key Terms:

Hox gene clusters
Gene duplication
Paralogous genes

Step-by-Step Guidance

Recall the typical number of Hox gene clusters in vertebrates.
Explain the evolutionary process (e.g., whole genome duplication) that increased the number of clusters.
Define 'paralogous' in this context.

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Q12. What is the role of Bmps during hand and digit development in vertebrate animals?

Background

Topic: Signaling Pathways in Development

This question is about the molecular signals that pattern limbs in vertebrates.

Key Terms:

BMPs (Bone Morphogenetic Proteins)
Apoptosis
Digit separation

Step-by-Step Guidance

Define what BMPs are and their general function in development.
Describe how BMPs influence the formation and separation of digits in vertebrate limbs.
Explain the cellular process (e.g., apoptosis) that BMPs regulate during this stage.

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Q13. Describe how plant growth and development are modular and (often) indeterminate.

Background

Topic: Plant Developmental Biology

This question is about the unique features of plant growth compared to animals.

Key Terms:

Modular development
Indeterminate growth
Meristems

Step-by-Step Guidance

Define 'modular' and 'indeterminate' in the context of plant development.
Explain how plants produce repeated units (modules) throughout their life.
Describe the role of meristems in supporting continuous growth.

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Q14. What is the first axis of development during plant development?

Background

Topic: Plant Embryogenesis

This question asks about the earliest spatial organization in developing plants.

Key Terms:

Apical-basal axis
Radial axis

Step-by-Step Guidance

Recall the main axes that organize plant bodies.
Identify which axis is established first during embryogenesis.
Describe what structures are defined by this axis.

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Q15. Plant development occurs in which tissue? What cells are present in this tissue?

Background

Topic: Plant Meristems

This question is about the tissues responsible for growth and development in plants.

Key Terms:

Meristem
Stem cells

Step-by-Step Guidance

Identify the tissue where most plant growth and development occurs.
Describe the types of cells found in this tissue and their properties.
Explain the significance of these cells for continuous plant growth.

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Q16. What are the four whorls of floral parts? During normal flower development, which is most external to the flower? Which is most internal to the flower?

Background

Topic: Flower Development

This question is about the organization of floral organs in angiosperms.

Key Terms:

Sepals
Petals
Stamens
Carpels

Step-by-Step Guidance

List the four whorls of floral organs in order from outermost to innermost.
Identify which whorl is most external and which is most internal.
Briefly describe the function of each whorl.

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Q17. Diagram the contribution/expression of the floral homeotic genes during development of each whorl of a flower. Based on your diagram, predict the result of loss-of-function mutations to class A, B and C genes.

Background

Topic: ABC Model of Flower Development

This question is about how combinations of homeotic gene expression specify floral organ identity.

Key Terms:

Class A, B, C genes
ABC model
Homeotic mutation

Step-by-Step Guidance

Recall the ABC model and which gene classes are expressed in each whorl.
Draw or mentally map out the gene expression pattern for each whorl.
Predict what happens to floral organ identity if class A, B, or C genes are nonfunctional.
Consider the phenotypes resulting from single or multiple gene class mutations.

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Q18. What is the evolutionary significance of the phenotype that results from the simultaneous knockout of all A-, B- and C-class genes?

Background

Topic: Evolution of Flower Structure

This question asks you to consider how loss of floral organ identity genes informs our understanding of flower evolution.

Key Terms:

Homeotic genes
Floral organ identity
Evolutionary significance

Step-by-Step Guidance

Recall what happens to floral organ development when all three classes of homeotic genes are knocked out.
Consider what this phenotype suggests about the ancestral state of flowers.
Explain how this informs our understanding of the evolution of floral organs.

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Q19. Define evolution in the context of population genetics.

Background

Topic: Population Genetics

This question is about the genetic definition of evolution at the population level.

Key Terms:

Evolution
Allele frequency
Gene pool

Step-by-Step Guidance

Recall the definition of evolution as it applies to populations, not individuals.
Express this definition in terms of changes in allele frequencies over time.
Relate this to the concept of the gene pool.

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Q20. For a single gene with two alleles, A1 and A2, mathematically describe the frequencies of each allele in the gene pool of a population.

Background

Topic: Allele Frequency Calculation

This question is about expressing allele frequencies mathematically.

Key Terms and Formulas:

Allele frequency: $p$ for A1, $q$ for A2
Relationship: $p + q = 1$

Step-by-Step Guidance

Assign variables to the frequencies of A1 and A2 (e.g., $p$ and $q$).
Write the equation that relates the two allele frequencies in a population.
Explain why the sum of the allele frequencies must equal 1.

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Q21. For the gene/alleles in the question above, mathematically describe the frequencies of all genotypes in the population assuming Hardy-Weinberg (H-W) equilibrium.

Background

Topic: Hardy-Weinberg Principle

This question is about predicting genotype frequencies from allele frequencies under H-W equilibrium.

Key Terms and Formulas:

Genotype frequencies: $p^2$ (A1A1), $2pq$ (A1A2), $q^2$ (A2A2)
Hardy-Weinberg equation: $p^2 + 2pq + q^2 = 1$

Step-by-Step Guidance

Recall the Hardy-Weinberg equation for genotype frequencies.
Assign $p$ to the frequency of A1 and $q$ to the frequency of A2.
Write the expected frequencies for each genotype (A1A1, A1A2, A2A2).
Explain why these frequencies must sum to 1.

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Q22. For the gene/alleles in the question above, what are the genotype frequencies in a population in H-W equilibrium for allele frequencies A1=0.5 and A2=0.5? What are the genotype frequencies for A1=0.2 and A2=0.8?

Background

Topic: Applying Hardy-Weinberg Equilibrium

This question asks you to calculate genotype frequencies given specific allele frequencies.

Key Formula:

$p^2$ (A1A1), $2pq$ (A1A2), $q^2$ (A2A2)

Step-by-Step Guidance

For the first scenario, set $p = 0.5$ and $q = 0.5$.
Calculate $p^2$, $2pq$, and $q^2$ for these values.
For the second scenario, set $p = 0.2$ and $q = 0.8$.
Calculate $p^2$, $2pq$, and $q^2$ for these values.
Check that the genotype frequencies sum to 1 in each case.

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Q23. What are the five conditions that must be met in order for a population to remain in H-W equilibrium?

Background

Topic: Hardy-Weinberg Assumptions

This question is about the requirements for a population to maintain constant allele and genotype frequencies.

Key Terms:

No mutation
No migration (gene flow)
Large population size (no genetic drift)
Random mating
No selection

Step-by-Step Guidance

List the five key assumptions of the Hardy-Weinberg model.
Briefly explain why each condition is necessary for equilibrium.
Consider what happens if any of these conditions are violated.

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Q24. What is the relationship between the selection coefficient of an allele or genotype and its relative fitness? What is the consequence for carrying an allele with a high selection coefficient? What is the consequence for carrying a genotype with low relative fitness?

Background

Topic: Selection and Fitness

This question is about how selection acts on alleles and genotypes in a population.

Key Terms and Formulas:

Selection coefficient ($s$): $s = 1 - w$
Relative fitness ($w$): The reproductive success of a genotype compared to the most fit genotype.

Step-by-Step Guidance

Define the selection coefficient and relative fitness.
Write the formula relating $s$ and $w$.
Explain what it means for an allele to have a high selection coefficient.
Describe the consequences for genotypes with low relative fitness.

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Q25. Describe how the two main components of mutation-selection balance interact.

Background

Topic: Mutation-Selection Balance

This question is about how mutation introduces new alleles and selection removes them from the population.

Key Terms:

Mutation rate
Selection coefficient
Equilibrium frequency

Step-by-Step Guidance

Describe how mutation introduces new alleles into a population.
Explain how selection acts to remove deleterious alleles.
Discuss how the balance between these two forces determines the equilibrium frequency of an allele.

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Q26. Is the study of Hubbard et al. (2016) an example of hypothesis-based or discovery-based science?

Background

Topic: Scientific Method in Genetics

This question asks you to classify a research approach as hypothesis-driven or exploratory.

Key Terms:

Hypothesis-based science
Discovery-based science

Step-by-Step Guidance

Recall the definitions of hypothesis-based and discovery-based science.
Consider the main goal and approach of the Hubbard et al. (2016) study.
Decide which category best fits the study and explain your reasoning.

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Q27. Describe how the founder effect and genetic bottlenecks differ, and how they are similar.

Background

Topic: Genetic Drift and Population Structure

This question is about two mechanisms that reduce genetic diversity in populations.

Key Terms:

Founder effect
Genetic bottleneck
Genetic drift

Step-by-Step Guidance

Define the founder effect and genetic bottleneck.
Describe how each process occurs in populations.
Compare and contrast their effects on genetic diversity.
Summarize their similarities and differences.

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Q28. Is the evolutionary history of Channel Island gray foxes primarily driven by genetic drift, non-random mating, mutation, or selection? Argue with your study partner(s) about this for a few minutes, then get back to work.

Background

Topic: Evolutionary Forces

This question asks you to evaluate which evolutionary force has had the greatest impact on a specific population.

Key Terms:

Genetic drift
Non-random mating
Mutation
Selection

Step-by-Step Guidance

Review the definitions and effects of each evolutionary force listed.
Consider the population size and history of the Channel Island gray foxes.
Evaluate which force is likely to have had the strongest influence, based on what you know about island populations.
Be prepared to justify your reasoning with evidence or examples.

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Q29. How might outbreeding result in reduced offspring fitness? Isn’t outbreeding supposed to be a good thing?

Background

Topic: Outbreeding Depression

This question is about the potential negative effects of mating between genetically distant individuals.

Key Terms:

Outbreeding
Outbreeding depression
Local adaptation

Step-by-Step Guidance

Define outbreeding and outbreeding depression.
Explain how crossing individuals from different populations can sometimes reduce fitness.
Discuss the role of local adaptation and genetic incompatibilities.

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Q30. How does census population size differ from the effective population size?

Background

Topic: Population Size in Genetics

This question is about the difference between the actual number of individuals and the number that contribute genes to the next generation.

Key Terms:

Census population size (N)
Effective population size (Ne)

Step-by-Step Guidance

Define census population size and effective population size.
Explain why Ne is often smaller than N.
List factors that can cause Ne to differ from N (e.g., unequal sex ratio, variation in reproductive success).

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Q31. Is genetic drift or selection a more powerful force for population evolution in small populations?

Background

Topic: Genetic Drift vs. Selection

This question is about the relative importance of random versus deterministic evolutionary forces in small populations.

Key Terms:

Genetic drift
Selection
Population size

Step-by-Step Guidance

Recall how genetic drift and selection operate in populations of different sizes.
Explain why drift is more influential in small populations.
Discuss the consequences for allele frequency changes in small populations.

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Q32. Is genetic drift or selection a more powerful force for population evolution in large populations?

Background

Topic: Genetic Drift vs. Selection

This question is about the relative importance of evolutionary forces in large populations.

Key Terms:

Genetic drift
Selection
Population size

Step-by-Step Guidance

Recall how the strength of genetic drift decreases as population size increases.
Explain why selection is more effective in large populations.
Discuss the implications for evolutionary change in large populations.

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Q33. In a medium-sized population, when would you expect a population’s evolutionary trajectory to be more influenced by drift versus selection? When would selection be more important than drift?

Background

Topic: Drift vs. Selection in Intermediate Populations

This question asks you to consider the interplay between drift and selection in populations of intermediate size.

Key Terms:

Genetic drift
Selection
Population size
Selection coefficient

Step-by-Step Guidance

Consider the relative strengths of drift and selection in medium-sized populations.
Think about how the selection coefficient ($s$) affects the outcome.
Describe scenarios where drift would dominate (e.g., small $s$) and where selection would dominate (e.g., large $s$).
Summarize the factors that tip the balance between drift and selection.