Lecture 1: Introduction to Course & Introduction to Meiosis

 

(See Syllabus for Introduction to Course)

 

Meiosis

 

I. Why is it important??                                            

 

            - Source of genetic variation

            - Determines transmission of genes

 

 

Definition:

Meiosis is the process by which the zygote chromosome number is halved during gamete

formation

 

           

II. The stages of meiosis

 

- Replication of chromosomes to chromatids (prior to Prophase I)

 

- Pairing of homologues (Prophase I)

-

 Exchange of genetic material among homologues, creating a new mixture of genes on chromosomes  

    (Prophase I)

- Homologous chromosomes line up facing each other along equator of cell or metaphase plate 

    (Metaphase I)

 

- Each of the two homologous chromosomes are pulled to different poles (Anaphase I)

- Each of the two chromatids for each homologue is pulled to different poles (Anaphase II)

- Each of the chromatids becomes the genetic content for a new (gamete) cell (end of meiosis)

 

 

Chromosomes- molecules of DNA that are in part composed of genes

 

Chromatid- daughter strands of replicated chromosomes that are held together at the centromere

 

Centromere- a specialized region of the chromosome to which spindle fibers attach

 

Homologous chromosomes- chromosomes that match in many ways, including gene content

 

IV. Summary

 

-Behavior of chromosomes during meiosis determines inheritance of genes or loci (which are on

            chromosomes)

 

 

V. Key Concepts/Terms

 

Meiosis, centromere, chromatid, chromosome, recombination, homologous chromosome

Figures/Tables from chapter 4: 5, 8, 12, 13, 15, 17, Table 2,

 

Homework Questions for Week 2 covering Lecture 1

1. Provide definitions for the following 5 terms

A. homologous chromosome

B. chromatid

C. meiosis

D. recombination

E. centromere

 

2-4. Problems from Chapter 4: 3, 14, 16, 17 (a-c)

 

5. If an individual has genotype Aa, draw all possible arrangements of the chromosomes and chromatids, containing the ÒAÓ locus at Metaphase I of Meiosis. What are the genotypes of the gametes produced? Do the same for an individual that is AaBb where the ÒAÓ and ÒBÓ loci are on different chromosomes. What are the genotypes of the gametes produced?