1. Unit 4 Meiosis and Genetics
Objectives
Understand offspring acquire genes by inheriting chromosomes from parents
Fertilization and meiosis alternate in a sexual life cycle
Meiosis reduces the number of chromosome sets
Meiosis and sexual reproduction are responsible for genetic variation, which is necessary for evolution

2. Sexual Reproduction Inheritence of Genes
-Two parents produce offspring
-Offspring have shared traits with family
Asexual Reproduction
-Asexual reproduction produces two offspring from a single parent
-Offspring are identical or Clones
-Genetic variation is minimal and due to mutations
Inheritence of Genes
-Genes are…
1. Genetic software that codes for specific proteins
2. Read much like a book with letters
3. Responsible for the raw material that is a species
(Nature via Nurture)
4. Located on Chromosomes called a locus
-Inheritence relies on…
1. Precise replication of DNA
2. Meiosis to maintain a chromosomal number specific to a species

3. The Behavior or Chromosomes is responsible for Genetic Variation in Sexually Reproducing Organisms
Chromosomes alternate between fertilization (2n or Diploid) and Meiosis (1n or Haploid)
Somatic Cells are all cells except sex cells
Sex Chromosomes determine male and female gender
All other chromosomes are called Autosomes

4. Other Sexually Reproducing Organisms
Alternation of Generations
No multi-cellular diploid cell

5. How does Meiosis differ from Mitosis???
(p. 254 – 255)
Homologs line up in the middle
Homologs Separate d

6. Origins of Genetic Variation 2. Independent Assortment of Chromosomes
1. Crossing Over
-Occurs in Prophase 1 (average of 1-3 events/chromosome)
-Creates Recombinant chromosomes
-Cross overs occure between nonsister homologs
2. Independent Assortment of Chromosomes
-One Paternal and one Maternal chromosome goes to each daughter cell
Occurs in Metaphase 1
-With 23 chromosomes there are 8.4 million different combinations
3. Random Fertilization