Pop Bead Meiosis Name:

Transcription

1 Pop Bead Meiosis Name: Name: Objective: The objective of this activity is to help you understand the steps of meiosis by modeling the process. After you have completed this activity you should understand how a diploid cell becomes four haploid sex cells. In addition, you should understand the steps involved in this process and be able to compare it to mitosis. Materials: A materials bag: 2 different color sets of pop beads, 8 centromeres, cell membrane cards, and dry erase markers. Be sure to take some paper towels to erase the marker lines along the way. Procedure: 1. Interphase: The preparation phase a. Remove all the beads from your supply bag and sort them out by color b. From each color set, make two large (10 bead) yellow and two large red chromosomes. Then make two small (5 bead) yellow and two small red chromosomes. Now put 1 of each color back into the bag. The remaining pipe cleaners represent your diploid cell (two sets of chromosomes are present - one from mom, and one from dad). c. Place them into the large cell at one end of the table How many chromosomes are in your diploid cell? Why are there two of each color? How many chromosomes are from the father of this cell? d. Remove the chromosome copies from the bag. e. Attach the copies to the originals at the magnet What structure does the magnet represent? What is a chromosome attached to its copy called? What do the individual beads represent? 2. Prophase I: Chromosomes have replicated and are attached to their sister chromatids f. Place the 2 homologous pairs in a group beside one another. What is the group of 4 chromosomes side-by-side called? What happens only in this phase causing genetic variation? (you ll only write it here but you ll model it during step 10 later in the activity) g. Draw the cell using colored pencils, match your pop bead colors! Make sure to add centrioles & spindle fibers.

2 3. Metaphase I: The centrioles & spindle fibers (aka the spindle) moves the homologous chromosomes to the middle of the cell h. Move the groups of homologous chromosomes to form a line in the middle of the cell. i. Draw your cell using colored pencils, add the spindle fibers and the centrioles. 4. Anaphase I: The spindle pulls the chromosomes apart j. Separate the homologous chromosomes to opposite ends of the cell k. Draw your cell using colored pencils (don t forget the spindle) 5. Telophase I: Homologous pairs separate The end of Meiosis I l. Move the chromosomes into the new cells in the middle of the table. What has remained together? Draw using your colored pencils should there be centrioles & spindle fibers? 6. Prophase II: New spindles attach to chromosomes. Meiosis II begins and simultaneously takes place in two cells Meiosis II is almost exactly like what other cellular process? What phase IS NOT PRESENT between telophase I & prophase II? If this process were present, what would have happened to the chromosomes? 7. Metaphase II: The spindle moves the chromosomes to the middle of the cell m. Move the chromosomes to the equator of the cell

3 What are these groups of chromosomes called? What is the spindle attached to on the chromosomes? Draw using your colored pencils now should you draw a spindle? 8. Anaphase II: The spindle pulls the chromosomes apart to opposite poles n. Separate the chromosomes to opposite ends of the cell. o. Draw your cell using colored pencils (don t forget the spindle/centrioles) 9. Telophase II: Production of 4 haploid (one set of chromosomes = 1n). The end of meiosis p. Move the chromosomes on each end of the cells to their new cells at the end of the table How many chromosomes are in the newly formed cells? How does this compare with the beginning number of chromosomes? What are these new cells called? Are these new cells diploid or haploid? Why? q. Draw your cell using colored pencils is there centrioles & spindle fibers now?

4 10. Crossing Over r. Go back and make your prophase I scenario again. Cross over two alleles (different variations of a gene) by swapping one, two, or three alleles on one yellow sister chromatid with one, two, or three alleles on a red sister chromatid. Remember, the number of alleles you swap must be the same on each chromosome, otherwise one chromosome would be incomplete and one would have too many. s. Draw the resulting chromosomes after your crossing over event, in the cell below. t. When finished, complete the remainder of the steps of meiosis I & II to get 4 gametes What is the difference in this outcome with crossing over to the one without crossing over? 11. The Zygote (the first moment after the sex cells sperm and egg fuse. A single cell before it starts to divide into a new organism) t. Find a classmate who has finished the activity as well, and pair one of your gametes with one of theirs. u. What is the genotype of the zygote? v. Is it identical to the parent?

5 Pre-Crossing Over Chromosomes Post-Crossing Over Chromosomes (eventual gametes)

6 Pre-Crossing Over Chromosomes Post-Crossing Over Chromosomes (eventual gametes)

7 Yellow Chromosome Alleles (LONG) A (short arm end) B C D E F G H I J (long arm end) Trait coded for by DNA sequence of that gene Brown eyes Hanging ear lobe Dimples Height (tall) Tongue Roller Widow s Peak Hitchhiker s Thumb Double Jointed Limbs No fast twitch muscle response Brown hair Red Chromosome Alleles (LONG) a (short arm end) b c d e f g h i j (long arm end) Trait coded for by DNA sequence of that gene Blue eyes Attached ear lobe No dimples Height (average or short) Non-tongue roller No widow s peak No hitchhiker s thumb Not double jointed Fast twitch muscle response Blond hair Yellow Chromosome Alleles (SHORT) K (short arm end) L M N O (long arm end) Trait coded for by DNA sequence of that gene Hazel eyes Non-singer s voice Long fingers Shorter second toe Shorter hamstring average to slower runner Red Chromosome Alleles (SHORT) k (short arm end) l m n o (long arm end) Trait coded for by DNA sequence of that gene Speckled eyes Singer s voice Short fingers Morton s toe Longer hamstring faster runner

8 Meiosis Guided Notes Terms (jot down the most important points that are presented in the pre-lab discussion): Chromosome Gene Allele Locus (loci is the plural) Homologous chromosome Sister chromatid Meiosis I Meiosis II Gamete (aka sex cell/germ cell) Autosomal cell (aka somatic cell) Genetic variation Crossing over Independent assortment Random fertilization Homozygous (dominant & recessive) Heterozygous