“Let’s Talk About Sex”-ual Reproduction: 'Let’s Talk About Sex'-ual Reproduction Parts, their functions and Meiosis Genome British Columbia, 2004 www.genomicseducation.ca


The Human Life Cycle:Why do we reproduce?: The Human Life Cycle: Why do we reproduce? http://www.biosci.uga.edu/almanac/bio_103/notes/apr_4.html


Sexual Reproduction: Sexual Reproduction 2 parents are required and can produce 1 or more offspring that are genetically different from either parent Benefits: creates genetic variation in a population which allows for evolution and adaptation as well as being able to battle parasites, viruses and bacterial pathogens; some species find it an enjoyable past-time! It also ensures your genes are passed on, like leaving something of yourself behind when you are gone! Drawbacks: requires more time and energy, produces smaller numbers of offspring generally, requires both parents be in the same place at the same time (must find a mate!) How does it happen?? You must learn a bit about the human structures first…..


Male Reproductive Organs: Male Reproductive Organs


Male Reproductive Structures and their Functions: Male Reproductive Structures and their Functions


Female Reproductive Organs: Female Reproductive Organs


Female Reproductive Structures and their Functions: Female Reproductive Structures and their Functions


Test Yourself….so to speak! Name that part!: Test Yourself….so to speak! Name that part! 1 2 3 4 5 6 7 8 9 10 1. Testis 2. Cowper’s Gland 3.Vas Deferens 4. Urethra 5. Epididymus 6. Oviduct 7. Ovary 8. Vagina 9. Uterus 10. Prostate Gland


Meiosis- The Process of making Gametes: Meiosis- The Process of making Gametes OVERVIEW: 1st Division is very important as it reduces the numbers of chromosomes by half . Prophase I has the homologous chromosomes (chromosomes that appear identical to one another because they carry the same genes, one comes from our mom, and the other comes from our dad.) crossing over to exchange material Metaphase I have the homologous pairs line up at the equator of the cell and in Anaphase I, the homologous chromosomes separate and thus reducing the chromosome number in each cell. 2nd Division of Meiosis is exactly like mitosis, except that 2 cells start off in prophase 2 and you end up with 4 daughter cells that are completely different from each other.


Meiosis in Detail: Meiosis in Detail Prophase I Homologous chromosomes thicken and attach to each other in a chiasma (chiasmata- plural) Crossing Over occurs between homologs The nuclear envelops disintegrates The spindle fibers form from centrioles that move to the poles of the cell


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Metaphase I Homologous chromosomes line up at the equator of the cell Spindle fibers attach to the chromosomes


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Anaphase I Homologous chromosomes separate from each other and go to opposite poles of the cell Sister chromatids do not separate


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Telophase I Spindle fibers disappear Nuclear envelope may reappear Cytokinesis occurs to create 2 cells having half the number of chromosomes of the parent cell


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Meiosis II –Prophase II * Same as mitosis – nuclear envelop disintegrates * Spindle fibers form and attach to each chromatid and the centromere of the chromosome


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Metaphase II Chromosomes line up at the equator of the cell


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Anaphase II The sister chromatids separate and move to opposite sides of the cell


Meiosis in Detail (cont’d): Meiosis in Detail (cont’d) Telophase II Nuclear envelopes reform and the spindle fibers disappear Chromosomes relax into fine threads Cytokinesis occurs BOTTOM LINE: **4 different haploid cells have been formed!


Meiosis = Genetic Variability?: Meiosis = Genetic Variability? This cell has 4 chromosomes = 2N and creates 4 different possible gametes. What happens when there are 6 chromosomes? How many possible different gametes can arise? Does it matter if there is crossing over, or not?


Meiosis: Spermatogenesis –Making Sperm: Meiosis: Spermatogenesis –Making Sperm Notice that the outcome of this meiosis shows no crossing over, only a shuffling of chromosomes and the maturation of sperm (crossing over occurs more often than not occurring at all) There are 4 different cells that arise from meiosis – each having only ½ the original amount of DNA


Meiosis: Oogenesis – Making Eggs: Meiosis: Oogenesis – Making Eggs There are still 4 different cells created, however, only 1 of them is used for fertilization * note: the first meiotic division starts at ovulation, while the second meiotic division is not complete until fertilization occurs! ** females are born with a preset number of potential gametes prior to birth


Comparing Mitosis and Meiosis: Comparing Mitosis and Meiosis Mitosis 1. begins with one cell 2. creates 2 identical diploid cells 3. has only 1 stage of division 4. DNA replicates before mitosis begins 5. Occurs in all body cells at some point of life 6. Crossing over is a rare event Meiosis 1. begins with one cell 2. creates 4 different haploid cells 3. has 2 stages of division 4. DNA replicates before meiosis begins 5. Occurs only in sex cells 6. Involves crossing over as a normal event


Sexual vs Asexual Reproduction: Sexual vs Asexual Reproduction Asexual 1. Requires only one parent 2. Creates offspring that are identical to the parent 3. Process may be by mitosis, spore formation, budding etc. 4. Harmful pathogens can wipe out entire colonies of organisms due to the same genetic make-up e.g bananas! 5. May decrease the organism’s evolutionary capacity 6. Usually occurs in organisms that are less complex 7. Requires less energy and time in raising the offspring Sexual 1. Requires two parents 2. Creates offspring that are different than the parents 3. Process occurs by meiosis, fertilization and then birth 4. Harmful pathogens cannot wipe out entire populations as there is a variety in genetic make-up 5. Increases the organism’s chance of survival and evolution 6. Usually occurs in organisms that are more complex 7. Requires more energy and time in raising the offspring


When Meiosis goes wrong?: When Meiosis goes wrong? What could possibly go wrong in meiosis? Often mistakes occur: Where? -in the first division, but can occur in the second division as well, usually in egg formation -


Bibliography and Credits: Bibliography and Credits http://www.biosci.uga.edu/almanac/bio_103/notes/apr_4.html Audesirk et al. Biology Life on Earth. Sixth Edition. Prentice Hall. 2002. http://www.accessexcellence.org/RC/VL/GG/index.html http://www.grad.ttuhsc.edu/courses/histo/notes/female.html http://www.biosci.uga.edu/almanac/bio_103/notes/apr_8.html http://www4.ncsu.edu/unity/users/b/bnchorle/www/index.htm