Question

activity 4.2 modelling chromosomes in meiosis
the process of meiosis results in the production of haploid cells. use model chromosomes to follow what happens to the chromosomes during the phases of meiosis.
materials

• models of homologous chromosomes

procedure

1. working in groups of four, obtain models of two pairs of homologous chromosomes from your teacher.
2. use your models to simulate what happens to two pairs of homologous chromosomes during meiosis. begin by arranging your models as chromosomes are lined up at the start of meiosis i. notice that there are more than one way that the chromosomes can align at meiosis i.
3. draw a sketch of your chromosome arrangements as you represent each phase. also, make note of steps that represent haploid cells and steps that represent diploid cells.

questions

1. which step represents the formation of a gamete? how many gametes were produced?
2. how would the different ways of aligning the chromosomes in meiosis i affect the final model cells produced? what is the significance of this?
3. if the model cell produced after meiosis were to undergo mitosis, how would the daughter cell compare to it?

gamete formation in animals
the products of meiosis are haploid gametes. in humans, the gametes are sperm and eggs. the process of sperm production is called spermatogenesis spur - mat - oh - gen - uh - sis, and the process of egg production is called oogenesis oh - oh - gen - uh - sis. both of these processes involve meiosis, but they take place in slightly different ways.
spermatogenesis
in most male animals, meiosis takes place in the testes. as shown in figure 4.15, the process of spermatogenesis starts with a diploid cell called a spermatogonium. beginning at puberty, spermatogonia reproduce by mitosis, and the resulting cells undergo meiosis to form four haploid cells. following meiosis ii, the cells undergo a final set of developmental stages to develop into mature sperm. the nucleus and certain molecules required by the cell are organized into a \head\ region. the midsection holds many mitochondria, which are an energy resource for the cell. finally, a long tail - like flagellum develops for locomotion.
spermatogenesis
figure 4.15 in spermatogenesis, four haploid sperm cells form from one diploid cell.

Explanation:

1. The step in meiosis II where the cells divide to form haploid cells represents the formation of gametes. In spermatogenesis, one diploid spermatogonium produces four sperm gametes.
2. Different ways of aligning chromosomes in meiosis I (independent assortment) lead to genetic variation in the final model cells. This is significant as it increases genetic diversity in offspring.
3. If the haploid model cell produced after meiosis underwent mitosis, the daughter cells would be genetically identical to the parent haploid cell and remain haploid.

Answer:

1. The step in meiosis II cell - division represents gamete formation. Four gametes are produced in spermatogenesis from one diploid cell.
2. Different alignments in meiosis I (independent assortment) affect genetic makeup of final cells. Significance is genetic diversity in offspring.
3. Daughter cells would be genetically identical and haploid like the parent cell.