1. 11.4 Meiosis Chromosome Number P323
Q: How many sets of genes are found in most adult organisms?
A: 2 complete sets of inherited
chromosomes & 2 complete sets of genes.

2. Humans have 23 pairs or 46 chromosomes .

3. Diploid Cells
Homologous-chromosomes that each have a corresponding chromosome from the opposite-sex parent
Diploid- two sets-2N
Haploid-one set-N

4. Meiosis-Reduction Division Only with Gametes-(sex cells)
Meiosis I and Meiosis II (PMAT 2 times)

5. Prophase I-each replicated chrom
Prophase I-each replicated chrom. pairs with its corresponding homologous chrom.
Tetrad- is formed (4 chromatids)
Crossing-over-exchange of alleles between homologous chromosomes and produces a new combination of alleles.

6. Metaphase I
Line up across middle.

7. Anaphase I
Pulled to opposite ends of the cell

8. Telophase I
Nuclear envelope forms
Cytokinesis occurs

9. Meiosis II
Prophase II-Chromosomes visible

10. Metaphase II
Line up middle

11. Anaphase II
Move to ends

12. Telophase II Nuclear envelope forms Cytokinesis divides
End up with 4 genetically different cells.

13. Zygote-fertilized egg.

14. Comparing Mitosis and Meiosis

16. Mitosis Meiosis General cells Genetically identical No crossing over
No pairing of homologous chrom.
1 division result 2 cells
Chrom. # remains same
Only sex cells (gametes)
Genetically different.
Crossing over
Yes pairing of homologous chrom.
2 divisions result 4 cells
Chrom. # reduced by ½

17. Gene Linkage
Q: How can 2 alleles from different genes be inherited together?
A: Alleles of different genes tend to be inherited together from 1 generation to the next when those genes are located on the same chromosome.

18. P171-175 skip #28, 29, 30, 32, 33, 34, 39 p176 extra credit Study for vocab quiz tomorrow.