1. Do Now 1. Staple your karyotype labs together with the one that has the actual karyotype on TOP and hand it in. 2. Please take out your POGIL and put it on your desk. 3. With people sitting around you, discuss why the human population is so different genetically. Do you have siblings? Do you look like your siblings at all? How is this possible? Do you look more like one of your parents than the other? Do you look a lot like your grandparents? Think about it!

2. Crossing Over Meiosis: Genetic Variation

3. Meiosis Overview -Meiosis is the process in which cells become gametes (sex cells such as sperm and egg) -Meiosis leads to genetic diversity in multiple ways. -What ways do you think this happens based on the POGIL activity you completed on Friday?

4. Sources of Genetic Diversity 1. Crossing Over: this process occurs during Prophase I of Meiosis and causes two homologous chromosomes to exchange segments of their sister chromatids. 1. Segregation: Alleles for a particular trait are going to separate and go into different gametes during meiosis. 1. Independent Assortment: The way that the homologous chromosomes line up during metaphase is random!

9. Gene Mapping Tracking crossing over helps determine where genes are located on the chromosome Genes that are far apart have a LESS chance of crossing over together Genes that are closer have a GREATER chance of crossing over together

10. Why do we care?

11. Gene Linkage and Disease Genes that stay together are said to be LINKED One gene can be identified as a MARKER that can infer the presence of the other gene This can be used in identifying disease predisposition

12. Lets take a closer look http://www.dnaftb.org/11/animation.html

13. Today’s Lab ● First we will do a crossing over worksheet ● In today’s lab, we will take a closer look at crossing over and “cross-over frequency”.. You will need… a partner! one die… That’s it! Lets get to it!

14. Do Now Take out your labs from yesterday and continue working on the analysis questions.

15. The Cell Cycle Interphase → Mitosis OR Interphase → Meiosis

16. Types of Reproduction ▪Living organisms reproduce by two methods –Asexual reproduction –Offspring are identical to the original cell or organism –Involves inheritance of all genes from one parent ▪Ex: Binary Fission of prokaryotes –Sexual reproduction –Offspring are similar to parents, but show variations in traits –Involves inheritance of unique sets of genes from two parents

17. Sexual Reproduction Overview in humans:  A sperm with 23 chromosomes will fertilize an egg with 23 chromosomes to form a zygote with 46 chromosomes.  The zygote will divide through the process of mitosis to become a multicellular organism whose cells contain 46 chromosomes.  To continue the life cycle, cells of the reproductive organs undergo meiosis, a process in which ½ the number of chromosomes are given to a sperm/egg.

18. So... We know how a zygote becomes multicellular and understand the process of mitosis, how can we create sperm and egg cells?

19. Ploidy  Ploidy= the number of sets of chromosomes in a cell.  Most mammals are diploid or 2n and have 2 of each chromosome (homologous pairs)  Polyploidy: more than 2 sets of chromosomes. - Strawberries are octoploid! (8n) - Some ferns have been said to have over 1,000 of each chromosome!!

20. Haploid vs. Diploid  Diploid (2n)- Normal body cells (called somatic cells) have 46 chromosomes’  Haploid (n)- Sex cells (called gametes) have 23 chromosomes

21. Haploid/Diploid numbers Try to answer the following questions: 1. How many chromosomes would be in the sperm of a goldfish? 2. How many chromosomes would a somatic cell of a fruit fly have? 3. What is the haploid number for a potato?

22. Aneuploidy  An abnormal amount of chromosomes resulting in a chromosomal disorder.  Caused by non-disjunction Most commonly-  Monosomy: having only 1 of a chromosome - Ex: 1 X chromosome gives one “Turner’s Syndrome”  Trisomy: having 3 of a chromosome - Ex: Trisomy 21- Downs Syndrome

24. Meiosis The goal is to take a diploid somatic cell and divide the number of chromosomes in half to create 4 haploid gametes that are genetically different.

25. Mitosis vs. Meiosis ▪Like mitosis, meiosis is preceded by interphase –Chromosomes duplicate during the S phase ▪Unlike mitosis, meiosis has two divisions –During meiosis I, homologous chromosomes separate –The chromosome number is reduced by half –During meiosis II, sister chromatids separate –The chromosome number remains the same – When sister chromatids separate, the strands are called daughter chromosomes

26. Meiosis Meiosis I:  Prophase I- synapsis occurs forming tetrads and crossing over occurs  Metaphase I- homologous chromosomes line up at the equator  Anaphase I- homologous chromosomes separate to opposite poles  Telophase I- each new nucleus has a haploid number of duplicated chromosomes

28. Meiosis Meiosis II  Prophase II-haploid number of chromosomes condense  Metaphase II- haploid number of duplicated chromosomes line up at equator  Anaphase II- sister chromatids are pulled to opposite poles  Telophase II- haploid number of non-replicated chromosomes arrive at the poles  Cytokinesis: 4 genetically different haploid cells are produced

31. Spermatogenesis vs. Oogenesis Spermatogenesis= production of sperm  1 cell → 4 sperm Oogenesis= production of ovum (egg)  1 cell → 1 ovum and 3 polar bodies

32. Drawing out Meiosis  With a partner: please draw out the steps of meiosis. I will come around and give you a specific diploid number that you should show. You should make all maternal chromosomes one color and paternal chromosomes a different color. Label the following at least

33. Do Now -Take out your meiosis drawing. - Do you have any questions about the quiz?