Meiosis and Life Cycles

Self-Incompatibility in Plants

A Review of Signal Transduction

Meiosis
• “ halving of cells ”
• Allows for mixing of genes, sexual reproduction, diversity:
-Independent Assortment of Chromosomes
-Crossing Over
-Random Fertilization

Terminology
• Haploid, 1N, gamete:
• Diploid, 2N, somatic cell:
Use the table to answer:
-Chromosome # of a frog ’ s egg.
-Chromosome # of a chimp liver
-Ask and answer at your table

Meiosis Overview and Essential
Vocabulary

Life Cycles: Group Jigsaw
• Dominant Generation
(haploid or diploid; gametophyte or sphorophyte)
• Stages where the organism is unicellular, multicellular
• Organism specific vocab
• Seed Plants, Ferns,
Mosses, Fungi

Meiosis I

Meiosis II

Meiosis in Human Male
• Organ: Testes
• Spermatogenesis
• Puberty-->Death

Meiosis in Human Female
• Ovaries
• Oogenesis
• Puberty-->Menopaus
– Meiosis I
– Meiosis II

Oogenesis: How many complete haploid cell are made?

Fertilization
• Union of Gametes
• Getting into the egg: lysosome in acrosomal process
• Signalling

Fertilization in Plants
• What is pollen?
• How could a plant end up being tetraploid?
• Identify the chromosome # for: endosperm, embryo, pollen grain, egg

Importance of Hormones
• In both plants and animals, hormones signal timing of reproduction
• Ex: Ethelyne— ripening; Auxin— growth (inhibits reproduction!)
• Most plant hormones are gaseous. Why?

Organization of Timing
• Dormancy
– Seeds:
• Hormone: Abscicic
Acid keeps dormant
• Hormone:
Giberellic acid stimulates growwth
• Cyclic
– Flowers:
• High ethylene concentrations promote flowering.
• What signals might cause hormone changes?
• Why might this be advantageous?

Organization of Timing

Sex Determination

Genes on X Chromsome
• Necessary for normal development.
• Must have an X!
• What happens to one of each of the X chromosomes in a human females cell?

• SRY
The Y chromosome
What if you have a defective Y?
What if you have an X and no second X or Y?

Who determines sex?

Gender vs. Sex?
• Is sex physically determined?
Chromosomally determined?
• Are these the same?
• How is gender different than sex?

Karyotype

Amniocentesis
• 14-16 week of pregnancy
Cost/benefit analysis
Are there other ways to determine the sex and health of the fetus?

Karyotyping Activity
• Summary in lab notebook
• Should know some of the chromosomal mutations for the AP test
• Arizona biology website http://www.biology.arizona.edu/human_bio/ activities/karyotyping/karyotyping.html

Back to Importance of Meiosis
• Mendel ’ s First Law:
– Segregation of chromosomes
– If this doesn ’ t work we call it nondysjunction!

Nondisjunction--how has meiosis gone out of balance. How could this lead to miscarriage of an embryo ?

Mendel ’ s Law of Segregation

Meiosis leads to variation
• Mendel ’ s law of independent assortment
• Crossing over
• Random Fertilization
Question: Why can ’ t two brothers and sisters
(not identical twins) end up exactly the same? Or can they???

Mendel ’ s Law of Independent
Assortment

Crossing oVer

Random Fertilization
• How does random fertilization further increase diversity?
• How are self-incompatibility genes important?

In small groups:
• Compare and contrast mitosis and meiosis.
• Use as much vocab as possible. Multiple choice questions use this.
• Develop 5 multiple choice questions requiring you to distinguish between these two proceses-you may use an electronic source!