Topic 10.1: Meiosis

Essential Idea:  Meiosis leads to independent assortment of chromosomes and unique composition of alleles in daughter cells.
At SHS, Topic 10.1 is taught in the following class unit(s):

Statements & Objectives:

10.1.U1  Chromosomes replicate in interphase before meiosis.
  • Identify tetrad, bivalent, sister chromatids and non-sister chromatids in diagrams of replicated chromosomes.
10.1.U2  Crossing over is the exchange of DNA material between non-sister homologous chromatids.
  • State that crossing over occurs during prophase I.
  • Define chiasmata.
10.1.U3  Crossing over produces new combinations of alleles on the chromosomes of the haploid cells.
  • State two consequences of chiasmata formation between non-sister chromatids.​
10.1.U4  Chiasmata formation between non-sister chromatids can results in an exchange of alleles.
  • Draw a diagram to illustrate the formation of new allele combinations as a results of crossing over.
  • Explain how crossing over between linked genes can lead to genetic recombinants.​
10.1.U5  Homologous chromosomes separate in meiosis I.
  • Contrast meiosis I with meiosis II.​
10.1.U6  Independent assortment of genes in due to random orientation of homologous chromosomes pairs in meiosis I.
  • Describe random orientation and independent assortment.
  • Given a parent cell genotype, determine the allele combinations that are possible in the gametes due to independent assortment and random orientation.​
10.1.U7  Sister chromatids separate in meiosis II.
  • Compare meiosis II with mitosis.​
10.1.S1  Drawing diagrams to show chiasmata formed by crossing over.
  • Draw a diagram to illustrate the process and result of crossing over.​
10.1.NOS  Making careful observations- careful observations and record keeping turned up anomalous data that Mendel’s law of independent assortment could not account for. Thomas Hunt Morgan developed the notion of linked genes to account for the anomalies.
  • Describe the experiment of Bateson and Punnett that lead to results that did not support Mendel’s law of independent assortment.
  • Describe the trends and discrepancies that led Morgan to propose the idea of linked genes.​
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." 
 John Muir,   1911