Question 19M.2.SL.TZ2.2
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.2.SL.TZ2.2 |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Identify, Outline | Question number | 2 | Adapted from | N/A |
Identify the stage of mitosis labelled X in the image, giving a reason.
[Source: Copyright 2002, The Trustees of Indiana University]
[1]
telophase because the chromosomes/chromatids have reached the poles
OR
«late» anaphase as some chromosomes/chromatids are still moving/tails visible ✔
OWTTE
Most were able to correctly state (late) anaphase or telophase but did not give a reason as clearly asked. Many students seem to have excellent eyesight as they claimed to see that the chromosomes were unwinding and that the nuclear membranes had formed. Please encourage the students not to go beyond what can be seen.
Outline the use of a karyogram during pregnancy.
[3]
a. is a photograph/diagram of homologous pairs of chromosomes that can be analysed ✔
b. information may be used to determine other chromosome abnormalities/changes in chromosome numbers/possible birth defects ✔
c. Down syndrome/trisomy can be detected if there are three copies of a chromosome Not just “Down syndrome”.
OR
accept any other valid example ✔
d. other missing or extra pieces of chromosomes can be detected ✔
e. sex can be determined as the Y chromosome is shorter than the X ✔ Or correct ref to X and Y.
Most knew what a karyogram was. However, the question was about use, which does not involve a detailed description, taking up half the space about how the sample was obtained and the risks involved. Most knew that it was to do with the chromosomes, few stated that it was a diagram or a picture of the homologous pairs. An explanation of how it is used to confirm sex was needed.
