Solved by a verified expert:Experiment 1: Following Chromosomal DNA Movementthrough MeiosisIn this experiment, you will model the movement of the chromosomes throughmeiosis I and II to create gametes.Materials2 Sets of Different Colored Pop-it® Beads (32 of each – these may beany color)(8) 5-Holed Pop-it® Beads (used as centromeres)Procedure:Part 1: Modeling Meiosis without Crossing OverAs prophase I begins, the replicated chromosomes coil and condense…1. Build a pair of replicated,homologous chromosomes. 10beads should be used to createeach individual sister chromatid(20 beads per chromosome pair).The five-holed beads representeach centromere. To do this…a. Start with 20 beads of thesame color to create yourFigure 3: Bead set-up. The blue beadsfirst sister chromatid pair.represent one pair of sister chromatidsand the black beads represent a secondFive beads must bepair of sister chromatids. The black andsnapped together for eachblue pair are homologous.of the four different strands.Two strands create the first chromatid, and two strands create thesecond chromatid with a 5-holed bead at the center of eachchromatid. This creates an “I” shape.b. Connect the “I” shaped sister chromatids by the 5-holed beads tocreate an “X” shape.© 2013 eScience Labs,LLC.All Rights Reserved 2.3.4.5.6.c. Repeat this process using20 new beads (of adifferent color) to create thesecond sister chromatidpair.Assemble a second pair ofreplicated sister chromatids; thistime using 12 beads, instead of20, per pair (six beads per eachcomplete sister chromatid strand).Figure 4: Second set of replicatedPair up the homologouschromosomes.chromosome pairs created in Step1 and 2. DO NOT SIMULATECROSSING OVER IN THIS TRIAL. You will simulate crossing over in Part2.Configure the chromosomes as they would appear in each of the stages ofmeiotic division (prophase I and II, metaphase I and II, anaphase I and II,telophase I and II, and cytokinesis).Diagram the corresponding images for each stage in the sections titled“Trial 1 – Meiotic Division Beads Diagram”. Be sure to indicate the numberof chromosomes present in each cell for each phase.Disassemble the beads used in Part 1. You will need to recycle thesebeads for a second meiosis trial in Steps 7 – 12.Trial 1 – Meiotic Beads Diagram:Prophase IMetaphase IAnaphase ITelophase I© 2013 eScience Labs,LLC.All Rights Reserved Prophase IIMetaphase IIAnaphase IITelophase IICytokinesisPart 2: Modeling Meiosis with Crossing Over7. Build a pair of replicated, homologous chromosomes. 10 beads should beused to create each individual sister chromatid (20 beads perchromosome pair). Two five-holed beads represents the centromere. Todo this…a. Start with 20 beads of the same color to create your first sisterchromatid pair. Five beads must be snapped together for each ofthe four different strands. Two strands create the first chromatid,and two strands create the second chromatid with a 5-holed beadat the center of each chromatid. This creates an “I” shape.b. Connect the “I” shaped sister chromatids by the 5-holed beads tocreate an “X” shape.© 2013 eScience Labs,LLC.All Rights Reserved c. Repeat this process using 20 new beads (of a different color) tocreate the second sister chromatid pair.8. Assemble a second pair of replicated sister chromatids; this time using 12beads, instead of 20, per pair (six beads per each complete sisterchromatid strand). Snap each of the four pieces into two five-holed beadsto complete the set up.9. Pair up the homologous chromosomes created in Step 7 and 8.10. SIMULATE CROSSING OVER. To do this, bring the two homologous pairsof sister chromatids together (creating the chiasma) and exchange anequal number of beads between the two. This will result in chromatids ofthe same original length, there will now be new combinations of chromatidcolors.11. Configure the chromosomes as they would appear in each of the stages ofmeiotic division (prophase I and II, metaphase I and II, anaphase I and II,telophase I and II, and cytokinesis).12. Diagram the corresponding images for each stage in the section titled“Trial 2 – Meiotic Division Beads Diagram”. Be sure to indicate the numberof chromosomes present in each cell for each phase. Also, indicate howthe crossing over affected the genetic content in the gametes from Part1versus Part 2.Trial 2 – Meiotic Division Beads Diagram:Prophase IMetaphase IAnaphase ITelophase I© 2013 eScience Labs,LLC.All Rights Reserved Prophase IIMetaphase IIAnaphase IITelophase IICytokinesisPost-Lab Questions1. In this experiment, how many chromosomes were present when meiosis Istarted?2. In this experiment, how many nuclei are present at the end of meiosis II?How many chromosomes are in each?© 2013 eScience Labs,LLC.All Rights Reserved 3. What is the ploidy of the DNA at the end of meiosis I? What about at theend of meiosis II?4. How are meiosis I and meiosis II different? List two reasons.5. Why do you use non-sister chromatids to demonstrate crossing over?6. What combinations of alleles could result from a crossover between BDand bd chromosomes?7. Identify two ways that meiosis contributes to genetic recombination.8. Why is it necessary to reduce the number of chromosomes in gametes,but not in other cells?9. Blue whales have 44 chromosomes in every cell. Determine how manychromosomes you would expect to find in the following:Sperm Cell:Egg Cell:Daughter Cell from Mitosis:Daughter Cell from Meiosis II:© 2013 eScience Labs,LLC.All Rights Reserved 10. Research and find a disease that is caused by chromosomal mutations.When does the mutation occur? What chromosomes are affected? Whatare the consequences?11. Diagram what would happen if sexual reproduction took place for fourgenerations using diploid (2n) cells.© 2013 eScience Labs,LLC.All Rights Reserved
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