BIOL1130 Lecture Notes - Lecture 11: Spermatogenesis, Gametogenesis, Oogenesis
Evolution & Selection – The inheritance of traits
Diploid = two copies of each chromosome
Haploid = one copy of each chromosome
Meiosis
• Cell division that causes the number of chromosomes in newly formed
cells to be reduced by half
• Stages during meiosis
o DNA replication
o Cell division (meiosis I)
o Cell division (meiosis II)
DNA replication
• Homologous chromosomes duplicate to form sister chromatids
Meiosis I
• Interphase I
o DNA replicates
• Early Prophase I
o Chromatids connected by centromere
• Prophase I
o Paired homologous chromosomes (synapsis)
o Crossing over
▪ Pair of homologous chromosomes – one chromatid of each
chromosome crosses over (reciprocal exchange)
▪ The point where they cross over is called a chiasma
▪ When the chromosomes split, there are new genetic
combinations on the chromosomes
o Recombination
• Metaphase I
o The chromosomes line up across the equator of cell in homologous
pairs, facing opposite poles
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