DP Biology (last assessment 2024)
Question 17N.2.HL.TZ0.05
| Date | November 2017 | Marks available | [Maximum mark: 4] | Reference code | 17N.2.HL.TZ0.05 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Describe, Explain | Question number | 05 | Adapted from | N/A |
05.
[Maximum mark: 4]
17N.2.HL.TZ0.05
(a)
Describe the process of crossing over.
[2]
Markscheme
a. occurs during prophase I/during meiosis
b. homologous chromosomes form bivalents/pair up
c. breakage and rejoining of chromatids
d. exchange «of DNA/alleles» between non-sister chromatids/homologous chromosomes
[Max 2 Marks]
(b)
Explain the reason for linked genes not following the pattern of inheritance discovered by Mendel.
[2]
Markscheme
a. «linked genes are» on the same chromosome
b. Mendel's genes were on different chromosomes
c. linked genes are inherited together
OR
no independent assortment
d. «linked genes» only separated by crossing over
OR
fewer recombinants than with unlinked genes
Reject sex-linkage
