MEOSIS & GENETIC VARIATION

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Created by
Sophie Walsh

Cards (10)

  • MEOSIS VS MITOSIS
    mitosis
    • produces cells w/ same no. of chromosomes as parent cell
    • Daughter cells genetically identical as no pairing/seperating of homologus chromosomes
    • Produces 2 daughter cells as only divides ONCE
    Meiosis
    • Produces cells with half the no. of chromosomes as parent cell
    • Daughter cells are genetically different
    • Produces 4 daughter cells
    • Only happens in reproductive organs
    • Produces gametes
  • Why is it important that meiosis produces haploid gametes?
    So gametes can fuse together to produce a diploid cell so that it gets both sets of chromosomes.
    Results in indépendant assortment
  • Processes that result In genetic variation:
    1. MUTATION= new alleles formed / genes deleted or added
    2. INDEPENDANT SEGREGATION= Shuffling of maternal and paternal chromosomes after Meiosis I providing different combinations of alleles/chromosomes
    3. CROSSING OVER = chromosomes in each homologus pair (bivalent) twist around each other forming chiasmata chromatids then swap over meaning they all have different combinations of alleles
  • Advantages of genetic variation
    • Makes some better adapted for survival meaning they can reproduce and pass on allele
    • Allows for changing of environment
  • In meiosis I the chromosome number is HALVED
  • DIPLOID CELL= Cell with pairs of chromosomes
  • HAPLOID CELL= Cell with individual chromosomes
  • INTERPHASE= Cell copies chromosomes / DNA replicates
    MEIOSIS I =
    1. prophase- Chromosomes are arranged into bivalent homologous pairs. Chiasmata forms and crossing over can occur here
    2. Metaphase-pairs line up along equator and attach to spindle fibres via centromere
    3. Anaphase- Pairs move to opposite poles, breaking the chiasmata
    4. Telophase- Chromosomes uncoil turning into chromatids producing 2 haploid cells
    MEIOSIS II- chromosomes recondense and pairs of sister chromatids that make up each chromosome are separated via centromere forming 4 genetically different haploid cells
  • Name 1 type of chromosome mutation
    Non-dysjunction
  • NON DISJUNCTION=failure of chromosomes to separate