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Punnett square crosses




Lab14 Mendelian Genetics Experiment 1 Punnett SquareCrosses;Attachment Preview;lab014exp001.doc Download Attachment;Experiment 1: Punnett square crosses;Materials;Red beads;Blue beads;Green beads;Yellow beads;2 100mL Beakers;Procedure;1. Set up and complete Punnett squares for each of the following crosses;(remember Y = yellow, and y = blue);Y Y and Y y;Y Y and y y;a) What are the resulting phenotypes?;2010 eScience Labs, Inc.;All Rights Reserved;b) Are there any blue kernels? How can you tell?;2. Set up and complete a Punnett squares for a cross of two of the F1 from 1b;above;a) What are the genotypes of the F2 generation?;b) What are their phenotypes?;2010 eScience Labs, Inc.;All Rights Reserved;c) Are there more or less blue kernels than in the F1 generation?;3. Identify the four possible gametes produced by the following individuals;a) YY Ss;b) Yy Ss;c) Create a Punnett square using these gametes as P and determine the;genotypes of the F1;d) What are the phenotypes? What is the ratio of those phenotypes?;4. You have been provided with 4 bags of different colored beads. Pour 50 of the;blue beads and yellow beads into beaker #1 and mix them around. Pour 50 of;the red beads and green beads in beaker #2 and mix them.;Attention!Donotpourthebeakerstogether.;2010 eScience Labs, Inc.;All Rights Reserved;#1 contains beads that are either yellow or blue.;#2 contains beads that are either green or red.;Both contain approximately the same number of each colored bead.;These colors correspond to the following traits (remember that Y/y is;for kernel color and S/s is for smooth/wrinkled);Yellow (Y) vs. Blue (y);Green (S) vs. Red (s).;A. Monohybrid Cross: Randomly (without looking) take 2 beads out of #1.;This is the genotype of individual #1, record this information. Do not;put those beads back into the beaker.;Repeat this for individual #2. These two genotypes are your parents;for the next generation. Set up a Punnett square and determine the;genotypes and phenotypes for this cross.;Repeat this process 4 times (5 total). Put the beads back in their;respective beakers when finished.;a) How much genotypic variation do you find in the randomly picked;parents of your crosses?;b) How much in the offspring?;2010 eScience Labs, Inc.;All Rights Reserved;2010 eScience Labs, Inc.;All Rights Reserved;c) How much phenotypic variation?;d) Is the ratio of observed phenotypes the same as the ratio of predicted;phenotypes? Why or why not?;e) Pool all of the offspring from your 5 replicates. How much phenotypic;variation do you find?;f);What is the difference between genes and alleles?;g) How might protein synthesis execute differently if there a mutation;occurs?;2010 eScience Labs, Inc.;All Rights Reserved;h) Organisms heterozygous for a recessive trait are often called carriers;of that trait. What does that mean?;i);In peas, green pods (G) are dominant over yellow pods. If a;homozygous dominant plant is crossed with a homozygous recessive;plant, what will be the phenotype of the F1 generation? If two plants;from the F1 generation are crossed, what will the phenotype of their;offspring be?;2010 eScience Labs, Inc.;All Rights Reserved;B. Dihybrid Cross: Randomly (without looking) take 2 beads out of beaker #1 AND 2;beads out of beaker #2.;These four beads represent the genotype of individual #1, record this;information.;Repeat this process to obtain the genotype of individual #2.;a) What are their phenotypes?;b) What is the genotype of the gametes they can produce?;Set up a Punnett square and determine the genotypes and;phenotypes for this cross.;c) What is your predicted ratio of genotypes? Hint: think back to our;example dihybrid cross;Repeat this process 4 times (for a total of 5 trials).;2010 eScience Labs, Inc.;All Rights Reserved;d) How similar are the observed phenotypes in each replicate?;e) How similar are they if you pool your data from each of the 5;replicates?;f);Is it closer or further from your prediction?;2010 eScience Labs, Inc.;All Rights Reserved;g) Did the results from the monohybrid or dihybrid cross most closely;match your predicted ratio of phenotypes?;h) Based on these results, what would you expect if you were looking;at a cross of 5, 10, 20 independently sorted genes?;i);Why is it so expensive to produce a hybrid plant seed?;2010 eScience Labs, Inc.;All Rights Reserved;j);In certain bacteria, an oval shape (S) is dominant over round and;thick cell walls (T) are dominant over thin. Show a cross between;a heterozygous oval, thick cell walled bacteria with a round, thin;cell walled bacteria. What are the phenotype of the F1 and F2;offspring?;5. The law of independent assortment allows for genetic recombination. The;following equation can be used to determine the total number of possible;genotype combinations for any particular number of genes;2g= Number of possible genotype combinations (where g is the number of;genes);1 gene;21= 2 genotypes;2 genes: 22= 4 genotypes;3 genes: 23 = 8 genotypes;Consider the following genotype;Yy Ss Tt;We have now added the gene for height: Tall (T) or Short (t).;a) How many different gamete combinations can be produced?;2010 eScience Labs, Inc.;All Rights Reserved;b) Many traits (phenotypes), like eye color, are controlled by multiple;genes. If eye color were controlled by the number of genes;indicated below, how many possible genotype combinations would;there be?;5;10;20;2010 eScience Labs, Inc.;All Rights Reserved;View Full Attachment


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