AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Students should be able to: complete diagrams showing the chromosome…
Full specification wording
Genetic diversity can arise as a result of mutation or during: Students should be able to: complete diagrams showing the chromosome content of cells after the first and second meiotic division, when given the chromosome content of the parent cell explain the different outcome of mitosis and meiosis recognise where meiosis occurs when given information about an unfamiliar life cycle explain how random fertilisation of haploid gametes further increases genetic variation within a species.
Meiosis produces four genetically different haploid cells, whereas mitosis produces two genetically identical diploid cells.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 8 of 8
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Meiosis produces four genetically different haploid cells, whereas mitosis produces two genetically identical diploid cells. In diagram questions, after meiosis I, draw half the original chromosome number, each still as two chromatids (one from each homologous pair). After meiosis II, draw the same number but as single chromosomes. In unfamiliar life cycles, meiosis occurs exactly where the chromosome number halves, regardless of whether the resulting cells are called gametes or spores. Finally, random fertilisation further increases genetic variation because any genetically unique male gamete can fuse with any genetically unique female gamete, creating novel allele combinations in the zygote.
What earns the marks
- Showing half the number of chromosomes, each as two chromatids, after the first meiotic division.
- Showing the correct number of single chromosomes in all four cells after the second division.
- Stating mitosis gives two genetically identical diploid cells and meiosis four genetically different haploid cells.
- Identifying meiosis in an unfamiliar life cycle at the point where the chromosome number is halved.
- Explaining that random fertilisation combines any two genetically different gametes, creating new allele combinations.
Common mistakes and how to put them right
Drawing chromosomes after meiosis I as single structures instead of pairs of chromatids.
Answering 'meiosis makes gametes' when asked for the difference in outcome between mitosis and meiosis, without stating haploid/diploid and genetic variation.
Saying random fertilisation increases variation without stating that the fusing gametes are genetically different and create new allele combinations.
Exam tips
- Count before you draw: the chromosome number halves once only, at the end of meiosis I.
- When explaining random fertilisation, state that 'any' male gamete can fuse with 'any' female gamete to produce new allele combinations.
Try the lesson
The start of the Genetic diversity can arise as a result of mutation or during: Students should be able to: complete diagrams showing the chromosome content of cells after the first and second meiotic division, when given the chromosome content of the parent cell explain the different outcome of mitosis and meiosis recognise where meiosis occurs when given information about an unfamiliar life cycle explain how random fertilisation of haploid gametes further increases genetic variation within a species. lesson, made from checked teaching notes for this specification point.
Have a go first
A parent cell has four chromosomes, two long and two short. After the first meiotic division, how many chromosomes are present in each of the two cells produced?
Listen
Meiosis produces four genetically different haploid cells, whereas mitosis produces two genetically identical diploid cells. In diagram questions, after meiosis I, draw half the original chromosome number, each still as two chromatids (one from each homologous pair). After meiosis II, draw the same number but as single chromosomes. In unfamiliar life cycles, meiosis occurs exactly where the chromosome number halves, regardless of whether the resulting cells are called gametes or spores. Finally, random fertilisation further increases genetic variation because any genetically unique male gamete can fuse with any genetically unique female gamete, creating novel allele combinations in the zygote. A strong answer earns marks for these points. showing half the number of chromosomes, each as two chromatids, after the first meiotic division. showing the correct number of single chromosomes in all four cells after the second division. stating mitosis gives two genetically identical diploid cells and meiosis four genetically different haploid cells. identifying meiosis in an unfamiliar life cycle at the point where the chromosome number is halved. Exam tip: Count before you draw: the chromosome number halves once only, at the end of meiosis I.
Key words
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chromosome content diagrams
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mitosis versus meiosis
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random fertilisation
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See every definition
- chromosome content diagrams
- Diagrams showing the chromosome content of cells after the first and second meiotic division, when given the chromosome content of the parent cell.
- mitosis versus meiosis
- Mitosis gives two genetically identical diploid cells and meiosis four genetically different haploid cells.
- random fertilisation
- Any genetically unique male gamete can fuse with any genetically unique female gamete, creating novel allele combinations in the zygote.
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Test your understanding of Genetic diversity can arise as a result of mutation or during: Students should be able to: complete diagrams showing the chromosome content of cells after the first and second meiotic division, when given the chromosome content of the parent cell explain the different outcome of mitosis and meiosis recognise where meiosis occurs when given information about an unfamiliar life cycle explain how random fertilisation of haploid gametes further increases genetic variation within a species.
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