1. Meiosis!
Meiosis
Gametogenesis
Genetic Recombination
Errors in Meiosis

2. Meiosis somatic cells (body cells) are diploid (2n)
they contain two copies of each chromosome
human somatic cells contain 46 chromosomes

3. Meiosis
meiosis is a special type of cell division that only occurs in the reproductive organs
meiosis results in the production of reproductive cells called gametes (sperm and eggs)

4. Meiosis gametes are haploid (n)
they contain only one copy of each chromosome
human gametes contain 23 chromosomes

5. Meiosis each human sperm or egg cell contains:
1 sex chromosome that determines the sex of the individual
22 autosomal chromosomes (autosomes) that determine everything else

6. Meiosis meiosis, involves the following phases: prophase I
metaphase I
anaphase I
telophase I
5) prophase II
6) metaphase II
7) anaphase II
8) telophase II

7. Mitosis
Meiosis I
Meiosis II

9. To do now….
Meiosis Crash Course
Meiosis Microviewers
Mieosis Cards

10. Lesson Outline √ Meiosis Gametogenesis Genetic Recombination
Errors in Meiosis

11. Gametogenesis the production of gametes Spermatogenesis
occurs in male testis
results in four
non-identical
sperm cells

12. Gametogenesis the production of gametes Oogenesis
occurs in female ovaries
results in the production of one viable egg and three non-viable eggs (polar bodies)

13. Gametogenesis the production of gametes Oogenesis
polar bodies result from unequal division of cytoplasm (there is only enough cytoplasm to support one viable egg)

15. Lesson Outline √ √ Meiosis Gametogenesis Genetic Recombination
Errors in Meiosis √

16. Genetic Recombination
a rearrangement of genetic material during meiosis
contributes to variation among generations (the variation can be a success or failure in the environment)

17. Genetic Recombination
two examples of genetic recombination are:
crossing over
independent assortment

18. Genetic Recombination
Crossing Over
occurs during prophase I
occurs between non-sister chromosomes in a tetrad
genetic information is exchanged between chromosomes of paternal and maternal origin

20. Genetic Recombination
Crossing Over
usually occurs between 2 – 3 times per chromosome (depending on length)

21. Genetic Recombination
Independent Assortment
occurs during prophase I
when chromosomes begin to line up, the chromosomes of maternal and paternal origin do not necessarily line up on the same side

22. Genetic Recombination
Independent Assortment
this separates the maternal and paternal chromosomes into different gametes

24. Lesson Outline √ √ √ Meiosis Gametogenesis Genetic Recombination
Errors in Meiosis √ √

25. Errors in Meiosis
errors in meiosis occur when the chromosomes fail to separate properly
this is known as non-disjunction and results in gametes with more or less than the haploid number of chromosomes a

26. Errors in Meiosis
Trisomy
one extra chromosome

27. a a

29. Errors in Meiosis Polyploidy
organisms with more than two complete sets of chromosomes (i.e. triploidy = 3n)
common in plants and produces sterile offspring

30. Lesson Outline √ √ √ √ Meiosis Gametogenesis Genetic Recombination
Errors in Meiosis
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Compare: mitosis and meiosis √ √ √