Challenging Questions about Heredity 2

1. A heterozygous individual shows an intermediate phenotype between two homozygotes. Which inheritance pattern best explains this observation, and which Mendelian law does it violate?

2. Two genes located close together on the same chromosome are inherited together more often than expected. This phenomenon violates which Mendelian principle?

3. A monohybrid cross is performed between two heterozygous individuals (Aa × Aa). Which Punnett square result correctly represents the expected genotypic ratio?

4. In a dihybrid cross AaBb × AaBb, assuming independent assortment, what fraction of offspring are expected to be heterozygous for both traits?

5. A cross produces 75% dominant phenotype and 25% recessive phenotype offspring. Which parental genotypes are most consistent with this data?

6. In peas, yellow (Y) is dominant to green (y), and round (R) is dominant to wrinkled (r). What is the probability of producing a green, wrinkled offspring from a cross YyRr × Yyrr?

7. A trait appears in every generation and affects males and females equally. What is the most likely mode of inheritance?

8. A pedigree shows affected males, no affected females, and transmission from carrier mothers to sons. Which inheritance pattern fits best?

9. In Labrador retrievers, coat color is determined by two genes: B/b and E/e. Dogs with genotype ee are yellow regardless of B/b genotype. This is an example of:

10. A cross involving recessive epistasis produces a phenotypic ratio of 9:3:4. What does this ratio indicate?

11. During which phase of mitosis do sister chromatids separate and move toward opposite poles?

12. Synapsis and crossing over occur during which stage of meiosis?

13. Which structure attaches chromosomes to spindle fibers?

14. Which process increases genetic variation by exchanging genetic material between homologous chromosomes?

15. How does metaphase I of meiosis differ from metaphase of mitosis?

16. What is the correct first step in preparing a human karyotype?

17. Why are cells arrested in metaphase for karyotyping?

18. A karyotype showing three copies of chromosome 21 indicates:

19. Which abnormality would most likely be detected using karyotype analysis?

20. A karyotype labeled 46,XY indicates:

21. Which components form the backbone of a DNA molecule?

22. DNA strands run antiparallel because:

23. If a DNA sample contains 20% adenine, what percentage of cytosine is expected?

24. Chargaff’s rules support which structural feature of DNA?

25. 25. Which enzyme synthesizes new DNA strands during elongation?