YOU WILL BE LEARNING THIS IN MORE DETAIL IN YOUR LAB SESSION. YOU ARE RESPONSIBLE FOR THE INFORMATION YOU LEARN IN LAB ON THE LECTURE EXAM.

Living things Reproduce

Living things pass on genetic information to the next generation. Sexual reproduction occurs when two individuals contribute gametes (sperm and egg) during fertilization to produce a new offspring. Since each gamete (haploid number) must only contain half the genetic material as the parent (diploid number of chromosomes), there must be a process that results in a haploid gamete.

Objectives

Describe the purpose of meiosis
Describe chromosome structure.
Describe the stages of meiosis and the major events that happen at each stage.
Describe how variability of gametes is produced in meiosis.
Describe the process of spermatogenesis and compare it to oogenesis.
Compare meiosis and mitosis.
Discuss the advantages and disadvantages of sexual reproduction vs. asexual reproduction.

Lecture Outline

I. Meiosis is the process that results in haploid gametes.

A. Chromosomes in more detail

Homologous chromosomes

Autosomes and sex chromosomes

Genes and alleles

Diploid and haploid numbers of chromosomes

B. Meiosis has two stages to ensure that the resulting gametes are haploid (more detail in lab).

a. Meiosis I – the important steps

Prophase I – homologous chromosomes synapse (bivalent/tetrad)

Crossing-over of chromosomes Þ variation of genetic information.

Metaphase I and Anaphase I – homologous chromosomes line up on

equatorial plane of the cell and then separate to the poles.

Independent assortment Þ variation of genetic information.

At the end of Meiosis I, the cells are haploid, but they still have

the sister chromatids attached, so the cells must go through Meiosis II.

b. Meiosis II – similar to Mitosis, but with the haploid number of chromosomes.

c. Variability of gametes occurs in meiosis due to:

Crossing-over in Prophase I and

Independent Assortment in Metaphase I and Anaphase I.

d. Spermatogenesis (sperm production) vs. Oogenesis (egg production).

II. Compare Meiosis and Mitosis and understand their similarities and differences.

What are the advantages of sexual reproduction vs. asexual reproduction?

III. Changes in Chromosome Number and Structure - "mistakes" during Meiosis

A. Aneuploidy

B. Change in chromosome structure

Deletion

Duplication

Inversion

Translocation

Study Questions (write out the answers based on lecture material and material from the text book)

1. What is the purpose of meiosis?

2. What is the genetic importance of this process?

3. In which cells does it occur?

4. What are genes?

5. What does the diploid number mean in reference to chromosome number?

6. What happens at the different stages of meiosis?

7. What are the products of meiosis?

8. How do recombinations of genes occur?

9. What are gametes?

10. How do the gametes compare to their parents in terms of genetic material?

11. How do mitosis and meiosis compare in terms of cells in which each occurs, stages, chromosome number and products?

12. What is the significance of meiosis and sexual reproduction in terms of variation?

13. How does aneuploidy occur in individuals? What are some of the affects of this?

14. What are the four types of mutations that occur in the structure of the chromosome?

15. What are some examples associated with these mutations?

USE THE REVIEW MATERIALS AT THE END OF THE CHAPTER

Go to the web site for the book and check out the study questions online.

http://highered.mcgraw-hill.com/sites/007352543x/student_view0/index.html

YOU MUST REFER TO YOUR LAB SESSION FOR ADDITIONAL INFORMATION