Question 19M.2.SL.TZ2.7b
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.2.SL.TZ2.7b |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | b | Adapted from | N/A |
Mendel found the same pattern of inheritance in all the crosses that he performed. Outline, with examples, different types of inheritance that produce non-Mendelian ratios.
[4]
a. some traits may involve many genes/be polygenic eg: height, skin colour «correct example required» ✔ Accept any verifiable examples of these types of inheritance.
b. linked genes/alleles of different genes on same chromosome ✔
c. «small numbers of» recombinant phenotypes due to crossing over «between linked genes» ✔
d. co-dominance of specific alleles/intermediate forms eg: pink flowers «from red and white ones»/blood groups «correct example required» ✔
e. sex-linked effects eg: colour blindness «correct example required» ✔
f. environmental influence on inheritance/epigenetics/methylation ✔
g. any other example of non-Mendelien inheritance with a specific example ✔
This question was less well answered. Students commonly indicated linked genes and sex-lined genes as examples of non-Mendelian inheritance. Accurate discussion of co-dominance was less frequent.
