Biology • Year 12 • Module 6 • Lesson 1
Mutation, Alleles and Genetic Change
Lock in the vocabulary that separates mutation (the source of new alleles) from meiosis and fertilisation (which reshuffle alleles that already exist).
1. Label the "where new alleles come from" diagram
The diagram below traces what a single DNA change can become — from molecular sequence, to a new allele in one cell, to a frequency change in a population gene pool. Write the missing labels into boxes A–H. Labels are drawn from the lesson's Key Terms and Cards 1–4. 8 marks
- A — the molecular change that produced the new sequence _______________________
- B — what a DNA change in a gene region can produce _______________________
- C — the named DNA region where the change occurred _______________________
- D — a single variant form of that gene _______________________
- E — population-level collection of every variant present _______________________
- F — the two processes that reshuffle the alleles already there _______________________ and _______________________
- G — process that may later change how common the new allele is _______________________
- H — whether the mutation was caused because the organism "needed" it (yes / no) _______________________
| Box | Your label |
|---|---|
| A | |
| B | |
| C | |
| D | |
| E | |
| F | |
| G | |
| H |
2. Term–definition match
The ten definitions below are shuffled. In the right-hand column write the matching term from this list: mutation, allele, gene, gene pool, locus, genetic variation, natural genetic change, induced genetic change, meiosis, fertilisation. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 2.1 | A change in the DNA sequence. The only routine source of brand-new alleles in a population. | |
| 2.2 | The total collection of alleles present in a population. | |
| 2.3 | A variant form of a gene found at the same locus on homologous chromosomes. | |
| 2.4 | A DNA region with a biological function, usually coding for a protein or functional RNA. | |
| 2.5 | The fixed position on a chromosome where a particular gene is located. | |
| 2.6 | Differences in genetic makeup between individuals in a population. | |
| 2.7 | Genetic change arising through processes such as mutation, meiosis, fertilisation and population processes. | |
| 2.8 | Genetic change caused or directed by human technologies such as cloning, recombinant DNA and gene editing. | |
| 2.9 | The cell division that reshuffles chromosomes and alleles via independent assortment and crossing over. | |
| 2.10 | The random combining of gametes from two parents to produce a new allele combination in the zygote. |
3. True or false — with correction
For each statement, circle T or F. If the statement is false, write the corrected version on the line. 8 marks (1 for T/F, 1 for the correction where needed)
3.1 Mutations occur because the organism needs to adapt to a new environmental pressure. T / F
3.2 Meiosis and fertilisation are the main routine source of brand-new alleles in a population. T / F
3.3 A gene pool refers to all the genes inside one diploid cell. T / F
3.4 Mutation creates a new allele; natural selection may later change how common that allele becomes. T / F
4. Function recall
Answer each in 1–2 sentences using precise terms from the lesson. 10 marks (2 each)
4.1 What is the function of mutation at the population level?
4.2 What is the function of meiosis with respect to existing alleles?
4.3 What is the function of fertilisation with respect to existing alleles?
4.4 What does the phrase "mutation is random with respect to need" mean?
4.5 What is the function of separating "natural" from "induced" genetic change at the start of Module 6?
5. Fill the blanks — the "antibiotic resistance" misconception fix
Fill each blank using the word bank below. Each word is used at most once. 8 marks (1 per blank)
Word bank: mutation · allele · randomly · selection · frequency · resistant · gene pool · need
It is sometimes claimed that bacteria mutate because they need to survive antibiotic treatment. That is incorrect. A (1) ____________ is a change in DNA sequence that occurs (2) ____________ with respect to (3) ____________ . In a bacterial population, a resistance (4) ____________ may already exist in some cells by chance, or arise by mutation before the antibiotic is ever applied. When the antibiotic is added, susceptible cells die but (5) ____________ cells survive and reproduce. Over generations, the resistance allele's (6) ____________ in the (7) ____________ rises. This change in frequency is the work of (8) ____________ , not of the antibiotic "instructing" any cell to mutate.
Q1 — Labelled diagram (8 marks)
A: mutation (a change in DNA sequence). B: a new allele. C: gene (or locus / DNA region). D: allele. E: gene pool. F: meiosis and fertilisation. G: natural selection (accept: drift / gene flow). H: No — mutation is random with respect to need; the environment does not direct the change.
Marking: 1 mark per box. For F, both processes are required to score the mark.
Q2 — Term–definition matches (10 marks)
2.1 mutation · 2.2 gene pool · 2.3 allele · 2.4 gene · 2.5 locus · 2.6 genetic variation · 2.7 natural genetic change · 2.8 induced genetic change · 2.9 meiosis · 2.10 fertilisation. 1 mark each.
Q3 — True / false with correction (8 marks)
3.1 False. Correction: mutations occur randomly with respect to need. The environment does not direct the exact change required; mutation happens first and selection may later change the frequency of an allele that happens to help.
3.2 False. Correction: meiosis and fertilisation usually reshuffle alleles that already exist; mutation is the routine source of genuinely new alleles.
3.3 False. Correction: a gene pool is the total collection of alleles in a population, not the genes inside one cell.
3.4 True. (No correction needed.)
Marking: 1 mark for T/F + 1 mark for correction where required.
Q4.1 — Function of mutation (2 marks)
Mutation introduces brand-new alleles into a population's gene pool by changing the DNA sequence of a gene [1]. Without mutation, populations would only ever have the alleles they started with, no matter how much meiosis and fertilisation shuffled them [1].
Q4.2 — Function of meiosis (2 marks)
Meiosis produces genetically different gametes from a single parent by recombining alleles already present through independent assortment and crossing over [1]. It generates variation in offspring without creating new alleles [1].
Q4.3 — Function of fertilisation (2 marks)
Fertilisation randomly combines two gametes from two parents to form a zygote, producing a new combination of existing alleles [1]. Like meiosis, it increases variation but does not normally create a new allele [1].
Q4.4 — "Random with respect to need" (2 marks)
It means the environment does not direct what mutation will occur, or instruct an organism to produce the exact change it requires [1]. Useful mutations are not produced on demand; they arise by chance, and selection may later increase their frequency if they happen to help [1].
Q4.5 — Function of separating natural vs induced change (2 marks)
It establishes natural sources of genetic change (mutation, meiosis, fertilisation, population processes) as the baseline before the module introduces deliberate human technologies (cloning, recombinant DNA, gene editing) [1]. This prevents students from confusing the two layers and prepares them to evaluate biotechnology against a natural reference [1].
Q5 — Cloze (8 marks)
(1) mutation · (2) randomly · (3) need · (4) allele · (5) resistant · (6) frequency · (7) gene pool · (8) selection. 1 mark per blank.