Unit 6: Model Systems and Genetic Analysis of Development - Practice Quiz

1 E. coli is most commonly classified as which type of organism?

2 Which feature makes E. coli a popular model organism for genetic studies?

3 A bacteriophage is a virus that infects which type of host?

4 Which classic experiment used bacteriophage to confirm DNA as the genetic material?

5 Neurospora crassa is best described as which kind of organism?

6 Studies on Neurospora led Beadle and Tatum to propose which hypothesis?

7 Saccharomyces cerevisiae, a common model organism, is a type of what?

8 Why is yeast considered a useful eukaryotic model organism?

9 Arabidopsis thaliana is widely used as a model organism for studying which group?

10 Which feature makes Arabidopsis attractive as a plant model system?

11 Drosophila melanogaster is commonly known by what name?

12 How many pairs of chromosomes does Drosophila melanogaster have?

13 Caenorhabditis elegans is which type of animal?

14 Which property of C. elegans is especially valuable for developmental biology?

15 The zebrafish used in genetics research has which scientific name?

16 Which feature makes zebrafish embryos particularly useful for study?

17 Which sequence correctly represents the life cycle stages of Drosophila?

18 During which stage does Drosophila undergo metamorphosis into the adult form?

19 Early Drosophila embryonic development is characterized by which unusual feature?

20 Which type of gene product, deposited by the mother, sets up the initial body axes in the Drosophila embryo?

21 A researcher wants to study the mechanism of DNA replication and gene regulation using a system with a short generation time and a fully characterized single circular chromosome. Which organism is the most suitable choice?

22 The Hershey–Chase experiment used bacteriophage T2 with radioactive labels to demonstrate that DNA is the genetic material. Which labels were used to track protein and DNA respectively?

23 Beadle and Tatum's work with Neurospora crassa led to the 'one gene–one enzyme' hypothesis. What key feature of Neurospora made it especially suitable for identifying biochemical mutants?

24 In Neurospora, tetrad analysis of ordered asci allows mapping of a gene relative to its centromere. Second-division segregation patterns arise from which event?

25 Saccharomyces cerevisiae can be maintained and studied in both haploid and diploid states. Why is this dual life cycle particularly advantageous for genetic analysis?

26 Yeast was the first eukaryote to have its complete genome sequenced (1996). Approximately how many genes does the S. cerevisiae genome contain?

27 Arabidopsis thaliana is the preferred model plant for genetics. Which combination of features primarily accounts for this preference?

28 The ABC model of floral development was largely elucidated using Arabidopsis. A mutation eliminating class A gene function is expected to produce which floral phenotype?

29 Drosophila melanogaster has been a genetic workhorse for over a century. How many pairs of chromosomes does Drosophila possess, aiding early cytogenetic mapping?

30 Polytene chromosomes found in Drosophila salivary glands are valuable for cytogenetics. How do these chromosomes form?

31 Caenorhabditis elegans is prized for developmental studies because of its invariant cell lineage. Approximately how many somatic cells does the adult hermaphrodite have?

32 Programmed cell death (apoptosis) was first genetically dissected in C. elegans. During normal development, exactly 131 cells die by apoptosis. Which feature of C. elegans made this precise counting possible?

33 Zebrafish (Danio rerio) is a leading vertebrate model for developmental genetics. Which feature makes it especially useful for observing early embryonic development?

34 A gene knockdown technique widely used in zebrafish involves antisense molecules that block translation or splicing of target mRNAs. These molecules are called:

35 Drosophila undergoes complete metamorphosis. What is the correct sequence of its developmental stages?

36 Adult structures such as wings, legs, and eyes of Drosophila develop from clusters of cells set aside in the larva. These structures are called:

37 The early Drosophila embryo undergoes rapid nuclear divisions without cytokinesis, producing a single cell with many nuclei. This stage is known as the:

38 The anterior–posterior axis of the Drosophila embryo is established by maternal-effect genes. Which maternal gene product forms an anterior gradient that specifies head and thorax structures?

39 Segmentation genes act in a hierarchy to subdivide the Drosophila embryo. What is the correct order in which these gene classes act?

40 Homeotic (Hox) mutations in Drosophila, such as Antennapedia, cause one body part to develop in place of another. This phenomenon is termed:

41 In Neurospora crassa, an ordered tetrad (octad) analysis of a cross between a wild-type and a mutant allele shows a second-division segregation (MII) pattern for the arg locus in 30% of asci. What is the map distance between the arg gene and its centromere?

42 A cross in Neurospora between two linked genes yields the following tetrad classes: Parental Ditype (PD) = 40, Nonparental Ditype (NPD) = 4, Tetratype (TT) = 56. Using the Perkins formula, what is the corrected map distance?

43 In a phage cross, two mutations m1 and m2 are examined. Recombinant plaques total 180 out of a total of 9000 progeny plaques scored. Since recombination in phage counts reciprocal products, what is the map distance between m1 and m2?

44 Benzer's classic rII system in bacteriophage T4 exploited which key selective feature to detect extremely rare recombinants?

45 In Drosophila, the anterior determinant bicoid mRNA is localized at the anterior pole. If bicoid mRNA were experimentally injected into both poles of a wild-type embryo, what phenotype is most expected?

46 The gap gene Krüppel, gap gene hunchback, and pair-rule gene even-skipped act in a hierarchy. A loss-of-function Krüppel mutation would most directly cause which defect?

47 In Saccharomyces cerevisiae, mating type is controlled by the MAT locus with silent cassettes HML and HMR. The phenomenon of mating-type switching in homothallic strains requires which endonuclease and which directionality rule?

48 In C. elegans, the invariant cell lineage produces exactly 959 somatic nuclei in the adult hermaphrodite. During development, more cells are generated than survive. This is resolved by programmed cell death governed by the core pathway involving ced-3, ced-4, and ced-9. A loss-of-function mutation in ced-9 would result in:

49 The heterochronic gene lin-4 in C. elegans was the first microRNA discovered. It regulates lin-14 by which mechanism, and a lin-4 loss-of-function produces what phenotype?

50 The ABC model of floral organ identity in Arabidopsis specifies four whorls. According to the model, if class B genes (AP3/PI) are lost by mutation, what organ identity results in whorls 2 and 3 (normally petals and stamens)?

51 In the ABC model, class A and class C genes are mutually antagonistic. In a class A (apetala2) loss-of-function mutant, C expands into all four whorls. What is the resulting floral formula from whorl 1 to whorl 4?

52 In an interrupted-mating (conjugation) experiment with an Hfr strain, four genes enter the recipient at these times: thr (5 min), leu (10 min), azi (17 min), ton (25 min). If a second Hfr strain with a different integration site transfers ton first, what does this indicate about the E. coli chromosome?

53 In a three-factor transductional cross using P1 phage in E. coli, co-transduction frequency between two markers is used to estimate distance. If markers a and b show 70% co-transduction while a and c show 20%, which relationship is most consistent (using the Wu formula where cotransduction decreases with distance)?

54 During early Drosophila embryogenesis, the first 13 nuclear divisions occur without cytokinesis. What is the correct term for this stage and its key structural feature?

55 Maternal-effect genes such as bicoid and nanos determine the phenotype of the offspring based on the mother's genotype. A cross of a homozygous bicoid mutant female () with a wild-type male () produces embryos that are:

56 Homeotic (Hox) genes of the Bithorax and Antennapedia complexes exhibit spatial colinearity. A dominant gain-of-function mutation in Antennapedia causing its ectopic expression in the head produces which classic phenotype?

57 Zebrafish (Danio rerio) are favored for developmental genetics partly due to optical transparency of embryos. A large-scale forward-genetics approach frequently used in zebrafish to identify developmental mutants is:

58 The FLP/FRT system in Drosophila enables mosaic analysis by generating homozygous mutant clones in an otherwise heterozygous animal. This is especially valuable for studying:

59 In yeast tetrad analysis of two genes, an investigator observes PD NPD, and TT is present at moderate frequency. What can be concluded about the two genes?

60 Drosophila undergoes complete metamorphosis. Adult structures arise from imaginal discs set aside during larval stages. During which process do these discs undergo eversion and differentiation into adult appendages?