1. Ch 10 AP Biology Meiosis and Sexual Life Cycles

2. Genetics and Inheritance
Heredity: transmission of traits with variation
Genes: segments of DNA, we inherit some from each parent
Gametes: Reproductive cells (plants and animals)
Locus: location of gene along a chromosome

3. Asexual vs. Sexual Reproduction
Single individual is parent all genetic info. Passed to offspring
No variation
Sexual
2 parents make offspring
Unique combo of genes
Variation
Parent
Bud

4. Karyotype: humans as an example Diploid (2n) 46 chromosomes, Haploid (n) 23 chromosomes
Autosomes
44 Chromosomes
22 pair = homologs
Sex chromosomes
2 Chromosomes, only parts are homologous
1 pair X and Y
Females XX
Males XY
Somatic Cells (diploid 2n)
46 Chromosomes, 23 pair
Gametes (haploid n)
23 Chromosomes, not paired
Reproductive Cells
Karyotype:
Stain DNA during mitosis (condensed)
Used to diagnose disease

5. Human Life Cycle and Chromosomes
Fertilization:
Haploid Sperm + Haploid Egg
Makes diploid Zygote
Zygote undergoes Mitosis and human matures
Gametes
Develop from germ cells in gonads
Ovaries and testes

6. Sexual Life Cycles Most fungi & some protists:
Alternation of Generations:
Plants
Some Algae
Sporohpyte
Multicellular diploid
Meiosis yields haploid spores
Spore
Haploid
Divides mitotically yields gametophyte
Gametophyte
Multicellular haploid
Mitosis yields gametes
Gametes
Haploid cell fusion yields next sporophyte
Most fungi & some protists:
Gametes fuse yields diploid zygote
Meiosis occurs w/out multicellular diploid offspring developing
Meiosis produces haploid cells (not gametes)
Haploid cells divide by mitosis and yield:
Unicellular decendants or
Haploid multicellular adult
Mitotically divides and yeilds gametes

7. Sexual Life Cycles Fig. 13-6
Key
Haploid (n)
Haploid unicellular or
multicellular organism
Diploid (2n)
Haploid multi-
cellular organism
(gametophyte) n
Gametes n n
Mitosis n
Mitosis
Mitosis n
Mitosis n n n n n
MEIOSIS
FERTILIZATION
Spores n
Gametes n
Gametes n
MEIOSIS
FERTILIZATION
Zygote
MEIOSIS
FERTILIZATION 2n 2n 2n 2n
Diploid
multicellular
organism
Zygote
Diploid
multicellular
organism
(sporophyte)
Figure 13.6 Three types of sexual life cycles 2n
Mitosis
Mitosis
Zygote
(a) Animals
(b) Plants and some algae
(c) Most fungi and some protists

8. Meiosis pgs. 198-199 Meiosis I: Meiosis II:
Separates Homologous Chromosomes
Meiosis II:
Separates sister Chromatids

9. Unique Components of Meiosis
Synapsis:
Replicated homologs pair up and are connected
Crossing Over:
Non-sister chromatids exchange pieces of DNA produces recombinant chromosomes
Prophase I: increases variation in a population

10. Unique Components of Meiosis
Metaphase I:
Homologs line up on the metaphase plate TETRADS

11. Unique Components of Meiosis
Separation of Homologs: Anaphase I
Sister chromatids stay together
Replicated homologs move to opposite poles of the cell

12. Unique Components of Meiosis
Telophase I and cytokinesis
Haploid daughter cells form but with 2 sister chromatids per chromosome
Not necessarily genetically identical because of crossing over

13. Unique Components of Meiosis
Prophase II – Telophase II and cytokinesis
Sister chromatids line up then separate to form chromosomes
4 non identical haploid cells are produced
variation

14. Origins of Genetic Variation
Independent Assortment of Chromosomes
Maternal and paternal homolog move into daughter cells of meiosis I separately
Crossing Over
Homologs trade DNA pieces in Prophase I
Random Fertilization
223 possibilities or 8.4 million for each egg or sperm, so 223 x 223 yields 70 trillion possibilities

16. Mitosis, Cell Cycle vs. Meiosis
Don’t forget the summary!