Genetics, Part I: Genes Review Questions

  1. What are alleles?  answer
  2. The F1 and F2 offspring of the cross AA X aa would show which genotype(s)?  answer
  3. In Mendel's crosses, which generation was always completely heterozygous?  answer
  4. If an individual with a dominant phenotype is crossed with an individual with a recessive phenotype, 4 of their 9 offspring show the recessive phenotype. What is the genotype of the first parent?  answer
  5. If two heterozygous parents have a homozygous recessive child, what is the probability that the second child will also be homozygous recessive?  answer
  6. What is meant by the word phenotype?  answer
  7. What is the genotype of a pea plant that shows the recessive phenotype?  answer
  8. If red flowers are dominant, how would you find out the genotype of a plant with red flowers? What kind of a cross would you perform?  answer
  9. Let A = red flowers, a = white flowers, B = round seeds, and b = wrinkled seeds. What combination of gametes could be produced by an individual that is heterozygous for both traits? answer
  10. Let A = red flowers, a = white flowers, B = round seeds, and b = wrinkled seeds. What would a plant look like that had the following genotypes: 1) AABb 2) AaBb 3) Aabb  answer
  11. Let A = red flowers, a = white flowers, B = round seeds, and b = wrinkled seeds. Suppose that an investigator did a dihybrid cross and observed 16 offspring. How many of these would you expect to have the phenotype red, round? How many are expected to have the phenotype white, wrinkled? How many are expected to have the phenotype white round? How many are expected to have the phenotype red, wrinkled? answer
  12. What phenotype ratio will be produced by the cross AaBb X aabb? answer
  13. What phenotype ratio is produced by a monohybrid cross? answer
  14. How many different kinds of gametes can be produced by an organism with the genotype AABb? AaBb? Aabb? answer
  15. What size Punnett square is needed to analyze the following types of crosses? 1) AABB X aabb 2) AaBb X aabb 3) AaBb X AaBb 4) aabb X aabb 5) AAbb X aaBB answer
  16. In humans, short fingers is dominant and long fingers is recessive. Widow’s peak is dominant and straight hairline is recessive. A short-fingered man with a straight hairline whose mother had long fingers married a long fingered woman with a widow’s peak. The woman’s mother had a straight hairline. What proportion of the offspring will be heterozygous for both traits? [hint - draw a pedigree with the information that you have]
  17. A and a are two alleles at a locus. B and b are alleles at a different locus on a different chromosome. Draw two possible alignment patterns during metaphase I of meiosis. answer
  18. List the possible genotypes and phenotypes of the human blood types. answer
  19. A bell-shaped curve of distribution is shown with which kind of inheritance? answer
  20. For each of the following, tell whether it is an example of simple Mendelian genetics (dominant/recessive), incomplete dominance, codominance, multiple alleles, genomic imprinting, polygenic inheritance, epistasis, pleiotropy, or none of these. A. height in garden peas B. ABO blood groups in humans C. height in humans D. pink flowers in heterozygous snapdragons E. Marfan syndrome
  21. What is epistasis? answer
  22. What is Marfan syndrome? answer
  23. Polygenic characteristics such as height have a genetic component and a(n) __________ component. answer
  24. In a polygenic model of inheritance, how many active alleles does AAbbCcddEE have? answer
  25. Suppose that each active allele for height adds 2 inches to the base height of a person and that the base height is 5’2". If height is determined by 4 loci, what is the maximum height of a person? answer