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Ch 13: Meiosis & Life Cycles

If you have 2 sets of chromosomes/cell then you are diploid (2n), but if you have 1 set of chromosomes/cell then you are haploid (1n).

disjunction chromosome number reduction

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Comparison

Increasing genetic variability: Crossing Over

synaptonemal complex

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Increasing genetic variability: Independent Assortment

Example 2n = 4 -> 4 different kinds of chromosome combinations

Increasing genetic variability: Independent Assortment

Example 2n = 6 ->

8 different kinds of chromosome combinations

Thus, the # of possible chromosome combinations after meiosis = 2x, where x = n = # of chromosomes in a haploid cell

So for your cells?

For your offspring’s diploid combination, combine the possibilities from both parents.

46.11

Meiosis: Human Sperm Formation

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46.11

Meiosis: Human Egg Formation

When are mitosis and meiosis used in eukaryotes?

Human (sexual)Life Cycle

Diploid-dominant

Haploid-dominant

Alternation of generations

and some protists and a few fungi

Spores

gametes = sperm, eggs

zygote = fertilized egg

(Note: many eukaryotes also or only use asexual reproduction)

But not all eukaryotes do that => 3 kinds of eukaryotic life cycles

adult

adult

adult

adult