3.3.U1 One of diploid nucleus divides by meiosis to produce four haploid nuclei.
- Compare divisions of meiosis I and meiosis II.
3.3.U2 The halving of the chromosomes number allows a sexual life cycle with fusion of gametes.
- Compare sexual and asexual life cycles.
- Explain why meiosis must occur as part of a sexual life cycle.
3.3.U3 DNA is replicated before meiosis so that all chromosomes consist of two sister chromatids.
- State that DNA is replicated in interphase before meiosis.
- Given a diploid number (for example 2n=4), outline the movement and structure of DNA through the stages of meiosis.
3.3.U4 The early stages of meiosis involves pairing of homologous chromosomes and crossing over followed by condensation.
- List three events that occur in prophase 1 of meiosis.
- Define bivalent and synapsis.
- Outline the process and result of crossing over.
3.3.U5 Orientation of pairs of homologous chromosomes prior to separation is random.
- Describe the attachment of spindle microtubules to chromosomes during meiosis I.
- Describe random orientation of chromosomes during meiosis I.
3.3.U6 Separation of pairs of homologous chromosomes in the first division of meiosis halves the chromosome number.
- Explain why meiosis I is a reductive division.
- State that cells are haploid at the end of meiosis I.
3.3.U7 Crossing over and random orientation promotes genetic variation.
- Explain how meiosis leads to genetic variation in gametes.
- State the the number of chromosome combinations possible due to random orientation is 2^n.
3.3.U8 Fusion of gametes from different parents promotes genetic variation.
- Outline the role of fertilization as a source of genetic variation.
3.3.A1 Non-disjunction can cause Down syndrome and other chromosome abnormalities. Studies showing age of parents influences chances of non-disjunction.
- Define non-disjunction.
- State the result of nondisjunction.
- Describe the cause and symptoms of Down syndrome.
- Explain the relationship between parental age and chances of non-disjunction.
3.3.A2 Description of methods used to obtain cells for karyotype analysis e.g. chorionic villus sampling and amniocentesis and the associated risks.
- Describe the two procedures for obtaining fetal cells for production of a karyotype.
3.3.S1 Drawing diagrams to show the stages of meiosis resulting in the formation of four haploid cells.
- Outline the events of prophase, metaphase, anaphase and telophase in meiosis I and meiosis II.
- Draw diagrams of cells in prophase, metaphase, anaphase and telophase in meiosis I and meiosis II.
3.3.NOS Making careful observations- meiosis was discovered by microscope examination of dividing germ-line cells.
- Discuss difficulties in microscopic examination of dividing cells.
- Describe the discovery of meiosis.