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1 Review Write a summary of each phase of meiosis Use Analogies Compare the chromosomes of a diploid cell to a collection of shoes in a closet. How are.

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Presentation on theme: "1 Review Write a summary of each phase of meiosis Use Analogies Compare the chromosomes of a diploid cell to a collection of shoes in a closet. How are."— Presentation transcript:

1 1 Review Write a summary of each phase of meiosis Use Analogies Compare the chromosomes of a diploid cell to a collection of shoes in a closet. How are they similar. What would make the shoe collection comparable to the chromosomes of a haploid cell 2 Review What are the principle differences between mitosis and meiosis 3 Review How does the principle of independent assortment apply to chromosomes Infer If two genes are on the same chromosome but usually assort independently, what does that tell you about how close together they are

2 CH 11 INTRODUCTION TO GENETICS 11.4 Meiosis

3 Diploid Cells  Two sets of homologous chromosomes  One chromosome 2 from mom and one chromosome 2 from dad  Somatic cells  All cells other than sex cells  “2n”.

4 Haploid Cells  Only one set of chromosomes  Gametes  “n”.

5 Meiosis  Similar in process to Mitosis  Forms gametes  Goes from 2n to n  Fertilization goes from n to 2n  Meiosis I  Meiosis II  Create FOUR haploid cells from ONE diploid cell.

6 Meiosis Phases  Interphase  Prophase 1  Metaphase 1  Anaphase 1  Telophase 1  Cytokinesis  Prophase 2  Metaphase 2  Anaphase 2  Telophase 2  Cytokinesis.

7 Chromosomes  Each chromosome consists of two copies ensuring that each new cell will have the same genetic information  The identical strands of DNA are each called chromatids and are held together by a centromere.

8 Interphase 1  Chromosome replicate.

9 Prophase 1  DNA coils up into Chromosomes  Nuclear membrane breaks down  Chromosomes pair up into Tetrads  Tetrad  Homologous pair.

10 Prophase 1  Crossing over may occur  Chromatids of the homologous chromosomes cross over one another  Crossed sections of the chromatids are exchanged.

11

12 Metaphase 1  Homologous Pairs Line up down center of cell.

13 Anaphase 1  Chromosome Pairs separate  Pulled to opposite poles of cell.

14 Telophase 1 and Cytokinesis  Nuclear membrane forms around each cluster of chromosomes  Cytokinesis occurs forming two cells.

15  Now have two daughter cells that are genetically different  Now are Haploid.

16 Prophase 2  Chromosomes become visible  Nuclear membrane breaks down  No additional crossing over.

17 Metaphse 2  Chromosomes line up in the center of each cell.

18 Anaphase 2  The paired chromatids separate.

19 Telophase 2 and Cytokinesis  Chromosomes arrive at poles  Nuclear envelope reforms  Cytokinesis occurs forming four cells.

20  Sperm  Male Gamete  Ova or Ovum (egg)  Female Gamete  Fertilization  When the two gametes combine  Zygote  Fertilized egg.

21 Mitosis vs. Meiosis  Creates 2 daughter cells  Cell is identical to parent  Diploid (2n)  1 division  Produces ‘body cells’ (somatic cells)  Creates 4 daughter cells  Genetically different from parent cell  Haploid (n)  2 divisions  Produces gametes  Crossing over  Genetic Variations.

22 You are “One in a Million”  Over 8 million possible gamete combinations from dad  Over 8 million possible gamete combinations from mom.

23 You are actually “One in 64 TRILLION”

24 Gene Linkage  The closer two genes are located on a chromosome the more likely those alleles will occur together  Less of a chance for crossing over to occur in between  Used to map out location of genes.

25 Gene Map

26  Haploid and diploid numbers are designated N and 2N. The table shows haploid or diploid numbers of a variety of organisms.  Copy the table and complete it and then use it to answer the questions on the next slide.

27 1. Calculate What are the haploid numbers for the fern and onion plants 2. Interpret Data In the table, which organisms diploid number is closest to a human 3. Apply Concepts Why is a diploid number always even 4. Evaluate Which organism’s haploid and diploid numbers do you find most surprising- why


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