AI generated Unit 3 flashcards

Here is the answer key for the questions:

1. What is the relationship between genes and phenotypes?
   Answer: Genes determine phenotypes by encoding for traits that manifest in observable characteristics.

2. Define a polygenic trait and provide an example.
   Answer: A polygenic trait is influenced by multiple genes, often resulting in a continuous variation in traits. An example is human height.

3. What does pleiotropy mean in genetics?
   Answer: Pleiotropy occurs when a single gene influences multiple, seemingly unrelated phenotypic traits.

4. How can pleiotropy and polygenic traits interact?
   Answer: A single gene can have multiple effects (pleiotropy) while also contributing to a polygenic trait, creating complex interactions affecting phenotype.

5. What are quantitative traits, and how are they measured?
   Answer: Quantitative traits show continuous variation and are measured on a scale, like height and weight.

6. How do mutations contribute to genetic variation?
   Answer: Mutations introduce new alleles into a population, creating genetic diversity that can lead to phenotypic variation.

7. Explain how genetic and environmental factors together create phenotypic variation.
   Answer: Genetic variation provides a range of possible phenotypes, and environmental influences can modify or emphasize certain traits within that genetic framework.

8. In oldfield mice, what gene and alleles determine coat color, and which color is dominant?
   Answer: The Mc1R gene with alleles B (brown) and b (tan) determines coat color, with brown being dominant.

9. What is the role of the Mc1R gene in coat color expression?
   Answer: The Mc1R gene encodes the melanocortin receptor protein, which activates a pathway leading to the production of eumelanin, giving a brown coat color.

10. Write the Hardy-Weinberg equation for allele frequencies. What do "p" and "q" represent?
    Answer: The equation is p+q=1p + q = 1p+q=1, where "p" represents the frequency of the dominant allele and "q" represents the frequency of the recessive allele.

11. Write the Hardy-Weinberg equation for genotype frequencies and define each term.
    Answer: The equation is p2+2pq+q2=1p^2 + 2pq + q^2 = 1p2+2pq+q2=1. Here, p2p^2p2 is the frequency of the homozygous dominant genotype, 2pq2pq2pq is the frequency of the heterozygous genotype, and q2q^2q2 is the frequency of the homozygous recessive genotype.

12. What does it mean for a population to be in Hardy-Weinberg equilibrium?
    Answer: It means that allele and genotype frequencies remain constant over generations in the absence of evolutionary forces, maintaining a fixed mathematical relationship.

13. List the five conditions required for a population to remain in Hardy-Weinberg equilibrium.
    Answer: The conditions are random mating, no natural selection, no genetic drift, no gene flow, and no mutations.

14. How does random mating affect Hardy-Weinberg equilibrium?
    Answer: Random mating ensures that alleles combine randomly, which helps maintain stable allele frequencies.

15. Define natural selection and explain its effect on allele frequencies in a population.
    Answer: Natural selection is the differential survival and reproduction of individuals with advantageous traits, leading to an increase in allele frequencies for those traits.

16. What is genetic drift, and how does it differ from natural selection?
    Answer: Genetic drift is the random change in allele frequencies due to chance, unlike natural selection, which is non-random and based on fitness advantages.

17. Explain gene flow and how it affects genetic variation between populations.
    Answer: Gene flow is the movement of alleles between populations, which makes populations more genetically similar and can introduce new alleles.

18. Define an adaptation and give an example of an adaptation related to predator avoidance.
    Answer: An adaptation is a feature that improves fitness and survival in a given environment. An example is echolocation in bats, which helps them avoid predators and find prey.

19. Describe stabilizing selection and its effect on genetic variation.
    Answer: Stabilizing selection favors intermediate phenotypes, reducing genetic variation by selecting against extreme traits.

20. What is directional selection, and how does it affect allele frequencies?
    Answer: Directional selection favors one extreme phenotype, shifting allele frequencies toward that phenotype and reducing genetic variation.

21. Define disruptive selection and describe its effect on intermediate phenotypes.
    Answer: Disruptive selection favors both extremes over intermediate phenotypes, increasing genetic variation by promoting divergence within the population.

22. What is a genetic bottleneck, and how does it impact genetic diversity?
    Answer: A genetic bottleneck is a sharp reduction in population size due to events like disasters, leading to reduced genetic diversity as only a small subset of alleles survive.

23. Explain the founder effect and how it can change allele frequencies in a new population.
    Answer: The founder effect occurs when a small group establishes a new population with different allele frequencies than the original population, often due to genetic drift.

24. How can gene flow both increase and decrease fitness in a population?
    Answer: Gene flow can introduce beneficial alleles that enhance fitness or harmful alleles that reduce fitness, depending on the specific environmental context.

25. Describe how genetic drift can lead to the random loss or fixation of alleles, particularly in small populations.
    Answer: Genetic drift causes allele frequencies to fluctuate randomly, and in small populations, this randomness can lead to the permanent loss or fixation of alleles over time, reducing genetic diversity.