Question 21M.2.SL.TZ2.2
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.SL.TZ2.2 |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Distinguish, Label, Outline, State | Question number | 2 | Adapted from | N/A |
The diagram shows the stages in the cell cycle.
State processes occurring during interphase.
[2]
a. DNA replication ✔
b. cell growth ✔
c. duplication of organelles/mitochondria / production of microtubules/protein synthesis ✔
Accept first two answers only.
There were several G2 comments about Q2a, as it could be said that several processes were occurring. Perhaps it should have been more specific. Two out of DNA replication, cell growth and duplication of organelles were expected for the two marks. A surprising number of candidates in all languages, confused 'processes' with 'phases' and stated that interphase consisted of G1, S and G2. Most managed to label prophase and anaphase correctly on the diagram as required in part (b). The answers to part (b) were generally clear, but some lost marks for not comparing the same point. For example 'Mitosis produces diploid cells, but meiosis produces gametes' did not score a mark. The mitotic index was well known.
Using the letter C, label the stage on the diagram where chromosome supercoiling occurs.
[1]
prophase ✔
The stage should be clearly labelled.
If more than one stage is shown the candidate does not receive a mark.
There were several G2 comments about Q2a, as it could be said that several processes were occurring. Perhaps it should have been more specific. Two out of DNA replication, cell growth and duplication of organelles were expected for the two marks. A surprising number of candidates in all languages, confused 'processes' with 'phases' and stated that interphase consisted of G1, S and G2. Most managed to label prophase and anaphase correctly on the diagram as required in part (b). The answers to part (b) were generally clear, but some lost marks for not comparing the same point. For example 'Mitosis produces diploid cells, but meiosis produces gametes' did not score a mark. The mitotic index was well known.
Using the letter M, label the stage on the diagram where sister chromatids migrate to opposite poles.
[1]
anaphase ✔
The stage should be clearly labelled.
If more than one stage is shown the candidate does not receive a mark.
There were several G2 comments about Q2a, as it could be said that several processes were occurring. Perhaps it should have been more specific. Two out of DNA replication, cell growth and duplication of organelles were expected for the two marks. A surprising number of candidates in all languages, confused 'processes' with 'phases' and stated that interphase consisted of G1, S and G2. Most managed to label prophase and anaphase correctly on the diagram as required in part (b). The answers to part (b) were generally clear, but some lost marks for not comparing the same point. For example 'Mitosis produces diploid cells, but meiosis produces gametes' did not score a mark. The mitotic index was well known.
Distinguish between the outcomes of a cell dividing either by mitosis or meiosis.
[2]
a. mitosis produces two daughter cells while meiosis four ✔
b. mitosis produces cells with same number of chromosomes (2n) while in meiosis they are halved (n) ✔
c. mitosis produces body cells but meiosis produces gametes
OR
mitosis produces genetically identical cells but meiosis does not ✔
Allow answers in a table.
Reference to both has to be present for the mark.
There were several G2 comments about Q2a, as it could be said that several processes were occurring. Perhaps it should have been more specific. Two out of DNA replication, cell growth and duplication of organelles were expected for the two marks. A surprising number of candidates in all languages, confused 'processes' with 'phases' and stated that interphase consisted of G1, S and G2. Most managed to label prophase and anaphase correctly on the diagram as required in part (b). The answers to part (b) were generally clear, but some lost marks for not comparing the same point. For example 'Mitosis produces diploid cells, but meiosis produces gametes' did not score a mark. The mitotic index was well known.
The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy. Outline how the mitotic index is calculated.
[1]
number of cells (seen under the microscope) undergoing mitosis divided by the total number of cells (observed in sample area) ✔
Can be given as a %.
There were several G2 comments about Q2a, as it could be said that several processes were occurring. Perhaps it should have been more specific. Two out of DNA replication, cell growth and duplication of organelles were expected for the two marks. A surprising number of candidates in all languages, confused 'processes' with 'phases' and stated that interphase consisted of G1, S and G2. Most managed to label prophase and anaphase correctly on the diagram as required in part (b). The answers to part (b) were generally clear, but some lost marks for not comparing the same point. For example 'Mitosis produces diploid cells, but meiosis produces gametes' did not score a mark. The mitotic index was well known.