Chromosome and Chromatid Counting Flashcards

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1. カード 1

   質問

   What does one DNA molecule mean when counting nuclear chromosomes?

   回答

   One double-stranded DNA molecule

   The two complementary strands together form one molecule in this counting convention. An unreplicated chromosome contains one such molecule.

2. カード 2

   質問

   How do sister chromatids differ from the two chromosomes in a homologous pair?

   回答

   Sisters are the two products of replicating one chromosome; homologs are the corresponding chromosomes in a diploid pair.

   A replicated homologous pair therefore contains two chromosomes, each with its own sister pair.

3. カード 3

   質問

   Before sister chromatids separate, how is one replicated chromosome counted?

   回答

   One chromosome, two sister chromatids, two double-stranded DNA molecules

   Once the sisters separate, each is a daughter chromosome. This is a counting convention for the joined unit, not a claim that replicated sisters share a single copy of centromeric DNA.

4. カード 4

   質問

   Why must a chromosome-counting question say whether it means one cell, one nucleus, or one pole-bound group?

   回答

   Those boundaries can contain different numbers of chromosomes.

   Before cytokinesis is complete, two pole-bound groups or two re-formed nuclei can still lie inside one cell.

5. カード 5

   質問

   What does n represent in a chromosome count?

   回答

   The number of chromosomes in one complete haploid set

   A diploid complement is 2n. Replication produces sister copies without adding another homologous set.

6. カード 6

   質問

   For normal cell-division counting, what does “completed division, before the next S phase” specify?

   回答

   Chromosome segregation and cytokinesis are finished, and the resulting cells have not replicated DNA again.

   This avoids confusing a whole dividing cell with one final daughter cell.

7. カード 7

   質問

   A normal diploid cell has 2n = 6. In its G1 nucleus, how many chromosomes and double-stranded DNA molecules are present?

   回答

   6 chromosomes and 6 DNA molecules

   Each chromosome is unreplicated and contains one double-stranded DNA molecule.

8. カード 8

   質問

   In a normal diploid G1 nucleus, what are the ploidy and DNA amount? Let 1C mean the DNA amount in one unreplicated haploid set.

   回答

   2n and 2C

   The nucleus contains two homologous sets, each unreplicated. C measures DNA amount, not a number of molecules.

9. カード 9

   質問

   A normal diploid nucleus starts G1 with 2n = 8. Across one completed S phase, how do its chromosome and double-stranded DNA-molecule counts change?

   回答

   Chromosomes: 8 → 8. DNA molecules: 8 → 16.

   Each chromosome acquires two joined sister chromatids. Replication doubles the DNA-molecule count without doubling the conventional chromosome count.

10. カード 10

    質問

    A normal diploid cell has 2n = 6. After S phase is complete, in its G2 nucleus, how many chromosomes, attached sister chromatids, and DNA molecules are present?

    回答

    6 chromosomes, 12 sister chromatids, and 12 double-stranded DNA molecules

    The six replicated chromosomes each contain two sisters.

11. カード 11

    質問

    In one whole cell at normal mitotic metaphase, with starting diploid complement 2n = 8, how many chromosomes, attached sister chromatids, and nuclear DNA molecules are present?

    回答

    8 chromosomes, 16 sister chromatids, and 16 double-stranded DNA molecules

    Replication is complete, and the sisters are still joined.

12. カード 12

    質問

    A normal G1 nucleus has 2n = 10. A learner calls this “10 homologous pairs.” What is the correct pair count?

    回答

    5 homologous pairs

    The 10 counts individual chromosomes. Each homologous pair contains two chromosomes, so 10 ÷ 2 = 5.

13. カード 13

    質問

    A cell with starting diploid complement 2n = 6 is in normal mitotic anaphase: all sisters have separated, but cytokinesis is incomplete. Count daughter chromosomes and nuclear DNA molecules in the whole cell.

    回答

    12 daughter chromosomes and 12 double-stranded DNA molecules

    The six replicated chromosomes have separated into twelve daughter chromosomes. Both pole-bound groups are still inside the counted cell.

14. カード 14

    質問

    In a normal diploid G2 nucleus after completed replication, what are the ploidy and DNA amount? Let 1C mean the DNA amount in one unreplicated haploid set.

    回答

    2n and 4C

    There are still two homologous sets, but each chromosome is replicated. DNA amount has doubled from G1.

15. カード 15

    質問

    In normal meiosis, is there another S phase between meiosis I and meiosis II?

    回答

    No

    One completed replication precedes the two divisions. Meiosis II separates the sisters that remain joined after meiosis I.

16. カード 16

    質問

    A cell with diploid complement 2n = 8 completes normal mitosis and cytokinesis. Before another S phase, count chromosomes and nuclear DNA molecules in one daughter cell.

    回答

    8 chromosomes and 8 double-stranded DNA molecules

    Each daughter receives one copy of every chromosome in the starting diploid complement.

17. カード 17

    質問

    Normal mitotic telophase has produced two re-formed nuclei, but cytokinesis is incomplete. Does “per nucleus” mean the same boundary as “per cell”?

    回答

    No

    One cell still contains both nuclei. A per-cell total includes the chromosomes in both nuclei; a per-nucleus count includes only one.

18. カード 18

    質問

    A cell with starting diploid complement 2n = 6 is in normal mitotic anaphase after all sisters separate. Count daughter chromosomes and nuclear DNA molecules in the group moving toward one pole.

    回答

    6 daughter chromosomes and 6 double-stranded DNA molecules

    Each pole-bound group receives one daughter chromosome from each of the six replicated chromosomes.

19. カード 19

    質問

    A normal diploid nucleus has 2n = 8. After completed S phase, a learner reports 16 chromosomes because DNA doubled. What chromosome count should replace 16?

    回答

    8 chromosomes

    There are 16 attached sister chromatids and 16 double-stranded DNA molecules, but each joined sister pair still counts as one chromosome.

20. カード 20

    質問

    One whole cell with starting diploid complement 2n = 8 is at normal metaphase I. How many homologous pairs, chromosomes, attached sister chromatids, and nuclear DNA molecules are present?

    回答

    4 homologous pairs, 8 chromosomes, 16 sister chromatids, and 16 double-stranded DNA molecules

    Each pair contains two replicated homologs; each homolog contains two sisters.

21. カード 21

    質問

    What separates in normal anaphase I, and how does that differ from normal mitotic anaphase?

    回答

    Anaphase I separates homologous chromosomes; mitotic anaphase separates sister chromatids.

    In meiosis I, each pole-bound chromosome still has its two sisters. In mitosis, separated sisters are daughter chromosomes.

22. カード 22

    質問

    A cell with starting diploid complement 2n = 6 has completed normal mitotic chromosome segregation. Two nuclei have re-formed, but cytokinesis is incomplete. Count chromosomes and DNA molecules in one nucleus.

    回答

    6 chromosomes and 6 double-stranded DNA molecules

    That nucleus encloses one complete daughter complement. The other nucleus is outside the requested boundary.

23. カード 23

    質問

    A cell with starting diploid complement 2n = 8 completes normal meiosis I and cytokinesis. Count chromosomes, attached sister chromatids, and nuclear DNA molecules in one resulting cell.

    回答

    4 chromosomes, 8 sister chromatids, and 8 double-stranded DNA molecules

    The cell has one homolog from each pair, with each chromosome still replicated.

24. カード 24

    質問

    A normal mitotic cell began with 2n = 8 and has finished sister separation. What happens to the total number of nuclear DNA molecules when cytokinesis divides it into two cells, before any new replication?

    回答

    The combined total stays 16; each daughter contains 8.

    Cytokinesis changes the cell boundary. It partitions existing DNA rather than making or removing DNA molecules.

25. カード 25

    質問

    One cell with starting diploid complement 2n = 8 is in normal anaphase I after homologs separate but before cytokinesis. Count chromosomes, attached sister chromatids, and nuclear DNA molecules in the whole cell.

    回答

    8 chromosomes, 16 sister chromatids, and 16 double-stranded DNA molecules

    Homologs move apart while each sister pair stays joined. Counting both pole-bound groups preserves the whole-cell total.

26. カード 26

    質問

    After normal reciprocal crossing over is complete, does it change the chromosome or DNA-molecule count at metaphase I?

    回答

    No

    It changes DNA sequence combinations, not the completed-stage counts. Sisters need not remain genetically identical after crossing over.

27. カード 27

    質問

    A cell with starting diploid complement 2n = 6 has completed normal mitotic segregation. Two nuclei have re-formed, but cytokinesis is incomplete. Count chromosomes and DNA molecules across both nuclei together.

    回答

    12 chromosomes and 12 double-stranded DNA molecules

    Each nucleus contains six. The requested total includes both nuclei inside the same cell.

28. カード 28

    質問

    A parent with diploid complement 2n = 8 completed normal meiosis I. In one of its two cells at metaphase II, count chromosomes, attached sister chromatids, and nuclear DNA molecules.

    回答

    4 chromosomes, 8 sister chromatids, and 8 double-stranded DNA molecules

    Each cell retained one replicated homolog per pair. No second replication occurred.

29. カード 29

    質問

    A cell with starting diploid complement 2n = 8 is in normal anaphase I after homologs separate. Count chromosomes, attached sister chromatids, and nuclear DNA molecules in the group moving toward one pole.

    回答

    4 chromosomes, 8 sister chromatids, and 8 double-stranded DNA molecules

    One replicated homolog from each of the four pairs moves toward that pole.

30. カード 30

    質問

    In a normal mitotic cell, all sisters separate at anaphase before cytokinesis. Why can the chromosome count rise while the nuclear DNA-molecule count stays unchanged?

    回答

    Existing sister copies become separate daughter chromosomes.

    Sister separation changes what counts as a chromosome; it does not synthesize DNA. Replication occurred earlier in S phase.

31. カード 31

    質問

    A normal diploid cell at mitotic metaphase contains 20 double-stranded nuclear DNA molecules in the whole cell. What is its diploid chromosome number, 2n?

    回答

    2n = 10

    Each of the replicated chromosomes has two DNA molecules, so 20 ÷ 2 = 10 chromosomes.

32. カード 32

    質問

    A parent had diploid complement 2n = 8. In one normal meiosis-II cell, all sisters have separated at anaphase II but cytokinesis is incomplete. Count daughter chromosomes and nuclear DNA molecules in that whole cell.

    回答

    8 daughter chromosomes and 8 double-stranded DNA molecules

    Its four replicated chromosomes have separated into eight daughter chromosomes. This counts both poles of one meiosis-II cell.

33. カード 33

    質問

    A parent with diploid complement 2n = 8 completes normal meiosis I, meiosis II, and both cytokineses. Before new replication, count chromosomes and nuclear DNA molecules in one final product.

    回答

    4 chromosomes and 4 double-stranded DNA molecules

    The product has one unreplicated haploid set.

34. カード 34

    質問

    A parent with diploid complement 2n = 8 completed normal meiosis I. Both resulting cells are now at metaphase II. How do chromosome and nuclear DNA-molecule counts in one cell compare with the totals across both?

    回答

    One cell: 4 chromosomes and 8 DNA molecules. Both cells: 8 chromosomes and 16 DNA molecules.

    All DNA molecules are double-stranded. Each meiosis-II cell contains one replicated haploid set.

35. カード 35

    質問

    During normal anaphase I, one pole-bound group contains 10 double-stranded nuclear DNA molecules, with sister pairs still joined. What was the starting diploid chromosome number, 2n?

    回答

    2n = 10

    Ten molecules make five replicated chromosomes at that pole. That group is one haploid set, so n = 5 and 2n = 10.

36. カード 36

    質問

    A parent had diploid complement 2n = 8. In one normal meiosis-II cell at anaphase II, all sisters have separated. Count daughter chromosomes and nuclear DNA molecules in the group moving toward one pole.

    回答

    4 daughter chromosomes and 4 double-stranded DNA molecules

    One daughter chromosome from each of that cell’s four replicated chromosomes moves toward the chosen pole.

37. カード 37

    質問

    A parent with 2n = 6 completes normal meiosis into four products. A learner counts 12 nuclear DNA molecules across all products and assigns 12 to each product. What belongs in one product before new replication?

    回答

    3 double-stranded DNA molecules

    Each product contains n = 3 unreplicated chromosomes. Twelve is the combined total across all four products.

38. カード 38

    質問

    A normal meiotic parent had 2n = 6. After meiosis I and cytokinesis, one resulting cell contains 6 nuclear DNA molecules. A learner predicts 12 at metaphase II. Repair the prediction.

    回答

    6 double-stranded DNA molecules at metaphase II

    There is no S phase between the two meiotic divisions. The cell keeps three replicated chromosomes, each with two molecules.

39. カード 39

    質問

    A cell with diploid complement 2n = 6 completes normal mitosis and cytokinesis. Before new replication, count chromosomes and nuclear DNA molecules across both daughter cells together.

    回答

    12 chromosomes and 12 double-stranded DNA molecules

    Each of the two daughters contains six. A combined total is larger than the count in either daughter.

40. カード 40

    質問

    One whole cell at normal metaphase II contains 7 chromosomes. What was the diploid chromosome number, 2n, of the parent that began meiosis?

    回答

    2n = 14

    At metaphase II, the cell contains one replicated haploid set, so its seven chromosomes represent n = 7.

41. カード 41

    質問

    After normal meiosis I and cytokinesis, what are the ploidy and DNA amount in one resulting cell? Let 1C mean the DNA amount in one unreplicated haploid set.

    回答

    n and 2C

    The cell has one homologous set, but every chromosome is still replicated.

42. カード 42

    質問

    A normal G1 nucleus has 2n = 6. A learner counts 12 DNA molecules because DNA has two strands. What is the correct nuclear DNA-molecule count?

    回答

    6 double-stranded DNA molecules

    One unreplicated chromosome contains one double helix. Counting its two strands separately confuses strands with the molecule convention used here.

43. カード 43

    質問

    A parent with diploid complement 2n = 8 completes normal meiosis into four products. Before new replication, count chromosomes and nuclear DNA molecules across all four products together.

    回答

    16 chromosomes and 16 double-stranded DNA molecules

    Each product has four unreplicated chromosomes. Four products × four chromosomes gives sixteen in total.

44. カード 44

    質問

    A normal diploid G2 nucleus contains 12 attached sister chromatids after complete replication. How many chromosomes did its G1 nucleus contain?

    回答

    6 chromosomes

    Twelve sisters form six replicated chromosomes in G2. S phase kept the chromosome count at six.

45. カード 45

    質問

    A normal meiosis-I product has one homolog from each pair, and every chromosome still has two sisters. A learner calls the cell diploid because of the sisters. Is that correct?

    回答

    No: the cell is haploid.

    Ploidy counts homologous sets. The sisters are replicated copies within its single set, so they do not make it diploid.

46. カード 46

    質問

    An unspecified normal eukaryotic nucleus contains 8 double-stranded DNA molecules. Is that enough information to decide whether it is haploid or diploid?

    回答

    No

    You also need its replication state and the organism’s haploid complement. Eight molecules could, for example, be eight unreplicated chromosomes or four replicated chromosomes.

47. カード 47

    質問

    After normal meiosis II and cytokinesis, before new replication, what are the ploidy and DNA amount in one final product? Let 1C mean the DNA amount in one unreplicated haploid set.

    回答

    n and 1C

    The product contains one haploid set of unreplicated chromosomes.

48. カード 48

    質問

    One final product of normal meiosis contains 5 double-stranded nuclear DNA molecules before new replication. What were n and 2n for the diploid parent?

    回答

    n = 5 and 2n = 10

    Each final chromosome is unreplicated and contains one molecule, so this product has a five-chromosome haploid set.

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Chromosome and Chromatid Counting Flashcards

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