Unit 1: Mendelian inheritance - Practice Quiz

1 Which pre-Mendelian theory proposed that offspring inherit a blend of parental traits?

2 Who proposed the germ-plasm theory of heredity?

3 The chromosome theory of inheritance states that genes are located on what structures?

4 What is an alternative form of a gene called?

5 Which Mendelian law states that two alleles separate during gamete formation?

6 An organism with two identical alleles for a gene is described as what?

7 In a monohybrid cross between two heterozygotes, what is the typical phenotypic ratio under complete dominance?

8 Which term refers to the observable expression of a trait?

9 Which type of trait usually falls into distinct categories?

10 Which of the following is a quantitative trait in humans?

11 Quantitative traits are commonly measured in which way?

12 What are polygenes?

13 Continuous variation is typically characterized by what pattern?

14 What does the multiple factor hypothesis propose?

15 Under the multiple factor hypothesis, individual contributing alleles often have what kind of effect?

16 What is the common name of Drosophila melanogaster?

17 Why is Arabidopsis thaliana widely used in plant genetics?

18 Which model organism did Gregor Mendel use for his classic inheritance experiments?

19 What type of organism is Escherichia coli?

20 Why are mice useful as model organisms for human genetics?

21 A red-flowered plant crossed with a white-flowered plant produces pink offspring. When the pink offspring are self-crossed, red and white phenotypes reappear. Which conclusion best challenges the pre-Mendelian blending concept?

22 A researcher repeatedly removes the tails of mice before breeding them, but their offspring continue to develop normal tails. Which historical idea is most directly contradicted?

23 Which observation most strongly supported the post-Mendelian chromosome theory of inheritance?

24 In peas, tallness () is dominant to dwarfness (). A tall plant crossed with a dwarf plant produces 48 tall and 52 dwarf offspring. What is the most likely genotype of the tall parent?

25 Two heterozygous plants are crossed for a trait showing complete dominance: . What is the probability that a dominant-phenotype offspring is heterozygous?

26 A plant with genotype is test-crossed with . Assuming independent assortment, what proportion of offspring will be ?

27 An dihybrid cross gives a ratio close to . Which condition is necessary for interpreting this result as independent assortment?

28 A heterozygous individual forms gametes carrying either or , but not both alleles together. Which Mendelian principle does this illustrate?

29 Which investigation is best suited to distinguishing a qualitative trait from a quantitative trait?

30 A crop trait shows continuous variation and changes noticeably with soil nutrition. Which interpretation is most appropriate?

31 Two genetically identical plants develop different heights when grown under different light conditions. What does this observation demonstrate?

32 A trait is controlled additively by three independently assorting gene pairs. If each contributing allele adds one unit to the phenotype, how many phenotypic classes are expected in the generation?

33 Why does a polygenic trait often approach a bell-shaped distribution in a large population?

34 In a two-gene additive model, produces the darkest phenotype and the lightest. Which genotype is expected to have the same intermediate phenotype as ?

35 Under the multiple factor hypothesis, two gene pairs contribute additively to kernel color. In an cross, what fraction of offspring is expected to show either one of the two extreme phenotypes?

36 An population for an additive trait controlled by two gene pairs follows the phenotypic ratio . Which group contains individuals with the intermediate phenotype?

37 A researcher wants to map an X-linked mutation rapidly using many offspring and easily observed adult traits. Which model organism is most suitable?

38 Which pairing of a model organism with an experimental advantage is correct?

39 Why was the garden pea particularly effective for Mendel's inheritance studies?

40 A study requires rapid analysis of mutations in DNA replication and a later test of their effects in a mammalian body. Which sequence of model organisms is most appropriate?

41 A breeder crosses two purple-flowered plants and obtains 3,012 purple-flowered and 1,004 white-flowered offspring. Which conclusion most directly distinguishes Mendelian particulate inheritance from the blending hypothesis?

42 A trait appears in every generation and affects males and females equally, but affected offspring are sometimes born to two unaffected parents. Which interpretation best reflects a post-Mendelian understanding of this pedigree?

43 Why did the chromosomal theory of inheritance strengthen Mendel's laws without replacing them?

44 Two genes assort independently. An individual with genotype is crossed with . If the offspring phenotypes occur as , , , and for the four phenotype classes, what is the strongest conclusion?

45 A plant heterozygous for two independently assorting genes is selfed. What fraction of the progeny is expected to be homozygous for at least one locus but heterozygous at the other?

46 In a cross , gene is completely epistatic to gene : any individual is yellow, while is black and is white. What phenotypic ratio is expected?

47 A monohybrid testcross produces 98 dominant and 102 recessive offspring. Which hypothesis is most consistent with this result?

48 A recessive disorder has a frequency of in in a randomly mating population under Hardy-Weinberg assumptions. What is the approximate carrier frequency?

49 Which observation most strongly indicates that a measured trait is quantitative rather than a simple qualitative Mendelian character?

50 In a population, the phenotypic variance for seed weight is units, while the variance attributable to genetic differences is units. What is the broad-sense heritability?

51 A quantitative trait has a phenotypic variance of and an environmental variance of . If dominance and epistasis are negligible, what is the narrow-sense heritability?

52 Two lines of maize have identical mean heights, but one line has much greater phenotypic variance. Which explanation is most defensible?

53 Assume four independently assorting loci contribute additively to skin pigmentation, with each contributing allele adding one unit. In a cross between two individuals heterozygous at all four loci, what is the probability of an offspring receiving exactly four contributing alleles?

54 A polygenic trait controlled by three loci, each with two additive alleles, is evaluated in a uniform environment. How many phenotypic classes are expected if every allele contributes equally and there is no dominance?

55 Under the multiple factor hypothesis, a trait shows seven phenotypic classes in the generation, ranging from zero to six effective alleles. How many independently segregating loci are assumed?

56 In an additive polygenic system with four loci, what is the expected proportion of individuals at either extreme phenotypic class?

57 Two true-breeding parents differ at five independently assorting additive loci controlling plant height. What fraction of offspring is expected to resemble either original parent at all five loci?

58 Which combination best explains why Drosophila melanogaster became a powerful organism for establishing chromosome-based inheritance?

59 A researcher needs a model for rapid analysis of gene function through controlled crosses, self-fertilization, and visible developmental mutants. Which organism is the most suitable among the listed models?

60 Which experimental feature makes E. coli especially useful for studying gene regulation but limits its direct use for analyzing Mendelian segregation?