From a piece of blank paper, cut out three sets of four cigar-shaped structures (a total of 12 structures). These will represent chromatids. Be sure each member of a set of four chromatids has the same length and girth. In set one, label two chromatids 'A' and two chromatids 'a.' Cut each of these chromatids about halfway across near their midpoint and slide the two 'A' chromatids together at the cuts, to form a single set of attached sister chromatids. Do the same for the 'a' chromatids. In the second set of four chromatids, label two 'B' and two 'b.' Cut and slide these together as you did for the first set, joining the 'B' chromatids together and the 'b' chromatids together. Repeat this process for the third set of chromatids, labeling them as 'D' and 'd.' You now have models for three pairs of homologous chromosomes, for a total of six chromosomes. Combining your work in steps (f) through (m), provide a written explanation of the connection between meiotic cell division and Mendel's law of independent assortment.

Key Concepts

Meiotic Cell Division

Meiotic cell division is a specialized form of cell division that occurs in sexually reproducing organisms, resulting in four genetically diverse gametes, each with half the number of chromosomes of the original cell. This process includes two rounds of division: meiosis I, where homologous chromosomes are separated, and meiosis II, where sister chromatids are separated. The outcome is crucial for genetic diversity, as it allows for the combination of genetic material from two parents.

Mendel's Law of Independent Assortment

Mendel's Law of Independent Assortment states that alleles for different traits segregate independently of one another during gamete formation. This principle is based on the behavior of chromosomes during meiosis, where the distribution of one pair of homologous chromosomes into gametes does not affect the distribution of another pair. This law explains the genetic variation observed in offspring, as traits are inherited independently.

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes, one inherited from each parent, that have the same genes at the same loci but may carry different alleles. During meiosis, these chromosomes undergo processes such as crossing over and independent assortment, which contribute to genetic diversity. The representation of chromatids in the question illustrates how homologous chromosomes can be manipulated to understand their behavior during cell division.