BIO 122 Lecture Notes - Lecture 9: Multicellular Organism, Mendelian Inheritance, Nondisjunction
Prior to Week 9 Class 2 – Chapter 13 Meiosis
• Know
o The difference between sexual and asexual reproduction
▪ Sexual requires 2 individuals, needs meiosis
▪ Asexual is done through mitosis
o That a zygote is a fertilized egg and is diploid
o What a gamete is
▪ Sex daughter cell
o What haploid and diploid refer to
▪ Haploid has one of each chromosome
▪ Diploid has one of each chromosome from each parent
o What a homolog is/what a homologous pair refers to
▪ Diploid, set of each chromosome from each parent
o What an allele is
▪ Different versions of same gene
o That gametogenesis refers to the process of producing gametes via meiosis and can differ between
species
o The overall stages and products of Meiosis
▪ Meiosis I
• 2 haploid daughter cells
▪ Meiosis II
• 4 haploid daughter cells
o The differences between Meiosis I and II & between Meiosis and Mitosis
▪ Meiosis creates non-identical haploid, mitosis creates identical diploids
▪ Meiosis 1 makes 2 haploids, meiosis 2 makes 4 haploids
o What crossing over is and when it occurs
▪ Early meiosis 1
▪ Homologous chromosomes exchange genes
o What the synaptoneamal complex and what synapsis refers to
▪ Synapsis is the pairing process by which homologous pairs come together
▪ Complex holds paired chromosomes together
o What a tetrad (or bivalent) is
▪ A pair of homologous chromosomes
o What chiasma (chiasmata, plural) refers to
▪ Crossing area of homologous chromosomes
o What nondisjunction refers to and how nondisjunction events in Meiosis I would result in a
different outcome than a nondisjunction event in Meiosis II
▪ Full set of homologous chromosomes comes to one side in anaphase
▪ Results in aneuploidy
▪ Meiosis 1
• 4 anueploid gametes
▪ Meiosis 2
• 2 anueploid gametes
o What aneuploidy is
▪ Uneven number of chromosomes
o What independent assortment refers to
▪ Gametes can be arranged in anyway in the cells and can move to either side
▪ Any gamete could be selected for the zygote
• Understand
o How sexual reproduction increases genetic variation
▪ crossing over
• new alleles made
▪ independent assortment
• new traits selected together
▪ mate selection
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