IB Biology HL 4.1.2 Causes of Genetic Variation
Practise analysing HL genetic-variation evidence, including mutation, meiosis, reproduction and limits on natural selection.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Exam points
- Analyse mutation and chromosome evidence as sources of genetic variation.
- Compare meiosis, random fertilisation and asexual reproduction as evolutionary mechanisms.
D4.1.2—Roles of mutation and sexual reproduction question 1
[Maximum number: 7]
Variation in genetically inherited characteristics is the basis for evolution.
Explain how genetic variation between the individuals in a species can be generated.
a. mutation (in genes/DNA generates variation)
b. base substitution / change to base sequence of gene / makes single nucleotide polymorphisms /SNPs
c. new alleles formed / different alleles of gene / multiple alleles
d. radiation/mutagenic chemicals/mutagens cause/increase the chance of mutation
e. meiosis (generates variation)
f. recombination/new combinations of genes/alleles produced by crossing over
g. independent assortment/random orientation of (pairs of homologous) chromosomes/bivalents
h. gametes/chromosomes/DNA/genes from two parents combined (in sexual reproduction)
i. random fertilization (increases genetic variation)
j. in reproductively/geographically isolated populations natural selection may differ
k. in small/isolated populations gene pools change/evolution occurs due to natural selection/genetic drift
I. disruptive selection can cause different varieties/variants/types/phenotypes to diverge transfer of genes (between bacteria) in plasmids
For mpf it is not enough just to state 'crossing over'.
Marking guidance:
Do not accept types of mutation other than substitution for mpb.
7 max
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