Unit 2: Chromosomal architecture, cell division and genetic principles - Practice Quiz

1 What are chromosomes primarily composed of?

2 What is each identical half of a duplicated chromosome called?

3 What is a chromonema?

4 What does the chromosome matrix surround?

5 How do chromomeres appear along a chromonema?

6 What is the main function of the centromere?

7 Which chromosome has its centromere near the middle?

8 Where are telomeres located?

9 Which structure is commonly associated with the formation of the nucleolus?

10 Which special chromosomes are unusually large and found in some insect salivary glands?

11 Lampbrush chromosomes are commonly observed in which cells?

12 According to the chromosomal theory of inheritance, genes are located on:

13 Who are credited with independently proposing the chromosomal theory of inheritance?

14 During which phase of the cell cycle is DNA replicated?

15 Which part of the cell cycle includes G1, S, and G2 phases?

16 During which stage of mitosis do chromosomes align at the cell equator?

17 What separates during anaphase of mitosis?

18 How many daughter cells are normally produced by one mitotic division?

19 What is the usual result of meiosis from one diploid parent cell?

20 During which stage of meiosis does crossing over usually occur?

21 A chromosome is most compactly organized during metaphase. Which structural arrangement best explains this condensation?

22 A researcher observes thin, coiled threads within a chromosome during early prophase. These threads are most likely the:

23 If the protein framework supporting chromatin organization were disrupted, which chromosome component would be most directly affected?

24 Bead-like thickenings are visible along a chromosome thread during early prophase. What is the most appropriate interpretation?

25 A chromosome has its centromere positioned near one end, producing one very short arm and one long arm. Which chromosome type does this describe?

26 A chromosome fails to move toward either pole during anaphase because spindle microtubules cannot attach properly. Which region is most likely defective?

27 A chromosome displays a secondary constriction associated with the formation of the nucleolus. This region is commonly called the:

28 A cell line shows progressive chromosome shortening after repeated divisions. Which chromosome structure is most directly associated with protection from end-to-end fusion?

29 Polytene chromosomes in certain insect tissues are unusually large and show distinct banding patterns because they result from:

30 Lampbrush chromosomes are especially useful for studying gene activity in oocytes because they possess:

31 Which observation provides the strongest cytological support for the chromosomal theory of inheritance?

32 In a diploid organism, one homolog carries allele and the other carries allele . During meiosis, what happens to these alleles under normal segregation?

33 A cell contains twice as much DNA as it had in early , but its chromosome number has not changed. Which stage has it most likely completed?

34 A drug blocks formation of functional spindle fibers. At which cell-cycle stage would cells most directly fail to proceed normally?

35 A diploid cell with undergoes mitosis. How many chromosomes should each daughter cell contain after cytokinesis?

36 Sister chromatids are moving toward opposite poles of a dividing cell. Which event is occurring?

37 A mutation prevents the cell from forming two separate nuclei after chromosome segregation. Which mitotic stage is most directly affected?

38 A meiotic cell has chromosomes. How many chromosomes and chromatids are present in each cell immediately after meiosis I, before meiosis II?

39 Crossing over occurs between nonsister chromatids of homologous chromosomes. What is its main genetic consequence?

40 If homologous chromosomes fail to separate during meiosis I, the resulting gametes may contain abnormal chromosome numbers. This error is called:

41 A chromosome is experimentally treated so that its DNA remains intact but its histone proteins are removed. Which structural consequence is most likely?

42 A researcher observes a thin, coiled thread within a developing chromosome that becomes progressively more condensed during prophase. Which interpretation best fits this structure?

43 Suppose a chromosome matrix-associated protein is selectively disrupted during metaphase, while DNA replication and centromere function remain normal. Which outcome is most directly expected?

44 A meiotic prophase chromosome displays a reproducible series of bead-like thickenings along its length. Two homologues show matching bead positions, but one region contains an unusually large bead. What is the best inference?

45 A chromosome contains a functional kinetochore at an internal position but has a large DNA deletion on one arm. During mitosis, it segregates normally. Which conclusion is most justified?

46 A dicentric chromosome forms after a reciprocal exchange between two chromosomes. Which event most strongly predicts its breakage during anaphase?

47 A chromosome has a secondary constriction near one end that is associated with nucleolar formation. Which statement distinguishes this region from a telomere?

48 A chromosome end loses its telomeric repeats but retains a functional centromere. Which cellular consequence is most likely over successive cell divisions?

49 A giant chromosome from an insect salivary gland shows many aligned homologues, visible bands, and repeated DNA replication without cell division. Which combination best explains these features?

50 In an amphibian oocyte, a chromosome displays numerous lateral loops extending from a central axis. The loops are especially prominent during active RNA synthesis. What does this indicate?

51 A plant population contains an extra small chromosome that varies in number among individuals, carries mostly repetitive DNA, and is not required for normal survival. Which classification is most appropriate?

52 A diploid organism has genotype at one locus and produces gametes in which and occur in equal proportions. Which chromosomal event provides the direct cytological basis for this result?

53 Genes and are linked on the same chromosome, but recombinant gametes are detected. Which conclusion follows most directly from the chromosomal theory?

54 A cell has completed DNA replication but has not yet entered mitosis. Which description is correct?

55 A cell with irreparable DNA damage continues from G1 into S phase because a checkpoint pathway is defective. Which immediate risk is most likely?

56 A mitotic cell is treated with a drug that prevents kinetochore microtubules from attaching to chromosomes. Which checkpoint response should occur?

57 A diploid cell with undergoes mitosis. How many chromosomes and chromatids are present in one daughter nucleus immediately after telophase and cytokinesis?

58 A diploid organism has . At metaphase I, how many bivalents and chromatids are present in the nucleus?

59 Nondisjunction of one homologous pair occurs during meiosis I, while meiosis II proceeds normally. What gamete chromosome numbers are expected for that chromosome?

60 A crossover occurs between two loci on one pair of homologous chromosomes during prophase I. Which products are expected if no additional crossover occurs between those loci?