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,
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?