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Process of meiosis. CSCOPE Unit 08 Lesson 02. Asexual vs. sexual reproduction. Asexual vs. sexual reproduction. What is the advantage of an organism that reproduces sexually rather than asexually?

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Process of meiosis
Process of meiosis

CSCOPE

Unit 08

Lesson 02



Asexual vs sexual reproduction1
Asexual vs. sexual reproduction

  • What is the advantage of an organism that reproduces sexually rather than asexually?

    • An organism that reproduces sexually will have more genetic diversity than one that reproduces asexually.


Meiosis i
Meiosis i

  • Four Phases:

    • Prophase I

    • Metaphase I

    • Anaphase I (and)

    • Telophase I

  • Genetic diversity results from meiosis I.


Prophase i
Prophase I

  • Homologous (same) chromosomes pair (synapsis)

  • Homologous pairs called bivalents—two chromosome with four chromatids

  • Nuclear membrane dissolves

  • Chromosomes attach to spindle fibers and begin to move


Metaphase i
Metaphase I

  • Homologous chromosomes (bivalents) line up at the equator to form tetrads.

  • Random orientation results in diversity.

  • 50/50 chance of getting either parent’s homologue for each chromosome

Tetrad


Anaphase i
Anaphase I

  • Homologous chromosomes separate.

  • Chromosomes with TWO chromatids move to opposite poles.

  • Daughter cells will have 23 chromosomes (haploid) but with two chromatids.


Telophase i
Telophase I

  • Nuclear membrane begins to reform

  • Cell may quickly move to meoisis II


Meiosis ii
Meiosis II

  • Similar to mitosis BUT no synthesis phase (no DNA replication)

  • Chromatids are NOT identical because of crossing over (recombination).

  • Separates chromatids and produces two daughter cells with 23 chromosomes that have one chromatid each


Important concepts
Important Concepts!!!

  • Crossing Over: Exchange of genetic information between homologous chromosomes that results in recombinant chromosomes and genetic diversity


Important concepts1
Important Concepts!!!

  • Independent Assortment: Chromosomes randomly line up during metaphase I, and there are various ways that the homologous chromosomes may line up—again resulting in genetic diversity

http://www.mhhe.com/biosci/ap/ap_prep/bioD6.html


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