BRAINCAKEMeiosis and Sexual Reproduction
Revision notes for Meiosis and Sexual Reproduction in Edexcel Biology (8BI0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Sexual ReproductionSexual reproduction involves the fusion of two gametes (sex cells), usually from two different parents, to form a single cell called a zygote.
- GametesGametes are specialised sex cells that fuse at fertilisation.
- Formation of GametesGametes are made by a process called gametogenesis, which takes place in specialised reproductive organs: the testes and ovaries (the gonads) in…
- MeiosisMeiosis is a type of cell division that produces four haploid daughter cells from one diploid parent cell, each genetically different.
- Prophase 1Prophase I is the first and longest stage of meiosis.
- Metaphase 1In metaphase I the bivalents (pairs of homologous chromosomes) line up across the equator of the spindle.
- Anaphase 1In anaphase I the homologous chromosomes in each bivalent are separated.
- Telophase 1Telophase I is the final stage of the first meiotic division.
- Meiosis 2Meiosis II is the second division of meiosis.
- The Importance of MeiosisMeiosis matters for two main reasons: it keeps the chromosome number constant from one generation to the next, and it produces genetic variation.
- Chromosome MutationA chromosome mutation is a change in the structure or number of whole chromosomes, as opposed to a gene (point) mutation, which changes the base…
- Non-disjunctionNon-disjunction is the failure of chromosomes to separate correctly during meiosis.
- Down's SyndromeDown's syndrome is a genetic condition caused by an extra copy of chromosome 21.
- Turner's SyndromeTurner's syndrome is a condition affecting females in which one X chromosome is missing.
- SpermatogenesisSpermatogenesis is the production of sperm.
- OogenesisOogenesis is the production of egg cells in the ovaries.
- The Male GameteThe male gamete in mammals is the sperm cell (spermatozoon).
- The Female GameteIn mammals the female gamete released at ovulation is a secondary oocyte.
- Gametogenesis in PlantsIn flowering plants gametes are made inside the flower.
- Formation of PollenPollen grains develop inside the anthers of the stamens.
- Formation of Plant Egg CellsThe female gamete of a flowering plant, the egg cell, forms inside an ovule in the ovary of the carpel.
- PollinationPollination is the transfer of pollen grains from the anther to the stigma of a flower of the same species.
- Internal FertilisationFertilisation is the fusion of a haploid male gamete with a haploid female gamete to form a diploid zygote.
- External FertilisationIn external fertilisation, males and females release their gametes into the surrounding water and the gametes fuse outside the body.
- Fertilisation in HumansIn humans, sperm are deposited in the vagina and swim through the cervix and uterus into the oviduct, where fertilisation normally happens.
- Fertilisation in PlantsAfter pollination, a pollen grain on the stigma absorbs water and germinates.
- Embryo Development in MammalsAfter fertilisation in the oviduct, the zygote divides repeatedly by mitosis as it is moved towards the uterus by cilia and muscle contractions.
- DifferentiationDifferentiation is the process by which unspecialised cells become specialised for a particular function, for example a red blood cell, neurone or…