BIOL 111 Lab 10 Heredity Learning Objectives Describe the inheritance pattern of monohybrid and dihybrid crosses in Arabidopsis thaliana Safety Closed toe shoes and long pants must be worn Long hair tied back The plants are transgenic so please make sure to dispose of them in the appropriately labeled containers and bins Laboratory Topics Activities Lab Activity 1 Heredity in a Dihybrid Cross Lab Activity 2 1 Heredity in a Dihybrid Cross Using Previously Plated Seedlings Lab Activity 2 2 Heredity in a Dihybrid Cross Using a Simulation Lab Activity 3 Incomplete Dominance in Geraniums Page 1 of 10 Lab Activity 1 Genotype gl1gl1 gfp2gfp2 gl2gl2 gfp1gfp1 Heredity in a Dihybrid Cross Phenotype Glaborous Non fluorescent Trichomes Fluorescent 1 Observe the images of the adult plants of each of the parental lines gl1gl1 gfp2gfp2 and gl2gl2 gfp1gfp1 and note any differences you see below Visible differences between gl1gl1 gfp2gfp2 and gl2gl2 gfp1gfp1 plants Page 2 of 10 Observations 2 Observe the images of the plates of seedlings under royal blue light illumination Which parental line fluoresces Page 3 of 10 Note what part of the plant fluoresces if it fluoresces 3 Observe the images of the F1 seedlings from the cross of gl1gl1 gfp2gfp2 x gl2gl2 gfp1gfp1 using the dissecting scope and the royal blue light source What is the inheritance pattern for the glabrous phenotype dominant or recessive What is the inheritance pattern for the fluorescence phenotype 4 Construct a Punnett square for the original cross of the parental lines gl1gl1 gfp2gfp2 X gl2gl2 gfp1gfp1 Page 4 of 10 Gametes gl1 gfp2 gl1 gfp2 gl2 gfp1 gl1gl2 gfp1gfp2 gl2 gfp1 5 Based on your predicted genotype from question 4 what is the expected phenotype of the F1 Gametes gl1 gfp1 gl1gl1 gfp1gfp1 gl1 gfp2 gl2 gfp1 gl2 gfp2 gl1gl2 gfp1gfp1 gl1 gfp1 gl1 gfp2 gl2 gfp1 gl2 gfp2 6 Construct a Punnett square for the F2 What are the possible gametes for this cross 1 Hairy Glowy Trichomes and Fluorescent Requires at least one gl2 allele for trichomes and at least one gfp1 allele for fluorescence Page 5 of 10 Genotypes gl1gl2 gfp1gfp1 gl1gl2 gfp1gfp2 gl2gl2 gfp1gfp1 gl2gl2 gfp1gfp2 2 Glabrous Glowy No Trichomes Fluorescent Requires gl1gl1 for glabrous and at least one gfp1 allele for Genotypes fluorescence 3 Hairy Not Glowy Trichomes Non fluorescent Requires at least one gl2 allele for trichomes and gfp2gfp2 for Genotypes non fluorescence 4 Glabrous Not Glowy No Trichomes Non fluorescent Requires gl1gl1 for glabrous and gfp2gfp2 for non fluorescence Genotype gl1gl1 gfp1gfp1 gl1gl1 gfp1gfp2 gl1gl2 gfp2gfp2 gl2gl2 gfp2gfp2 gl1gl1 gfp2gfp2 Expected Phenotypic Ratio Based on the 4x4 Punnett square the expected phenotypic ratio for the F2 generation is Hairy Glowy 9 Glabrous Glowy 3 Hairy Not Glowy 3 Glabrous Not Glowy 1 CHECK WITH YOUR TA ABOUT WHICH LAB ACTIVITY 2 YOU ARE DOING Lab Activity 2 1 Heredity in a Dihybrid Cross Using Previously Plated Seedlings 1 Retrieve your group s plate of seedlings from week 8 from the bin on the TA desk Page 6 of 10 2 If the plate is badly contaminated and your plants did not grow do not open the plate Since our seedlings didn t grow as well as expected we will do a simulation but first you will observe what you can from your plates 3 Your group will be split into pairs to observe your seedlings a Pair One will use forceps to examine each seedling for the presence absence of trichomes under the dissecting scope using white light Use the images on page 1 as a reference Gently pick the seedling from the agar by grasping just below the leaves Once you have made a determination sort the seedling into either the dish labeled trichomes or the dish labeled no trichomes based on their phenotype Look carefully at the leaves Trichomes should be evident on the leaf surface if present You are encouraged to have two microscopes working at the same time Once you are done pass the dishes carefully over to pair two for fluorescence analysis Dispose of your empty agar plate in the biohazard bag b Pair Two will observe the seedlings under royal blue light illumination to detect the presence absence of fluorescence Use the images on page 1 as a reference You will need to carefully make your observations for each seedling and keep track of the phenotypes Pick up each sorted seedling with forceps and observe it under blue light One person should be responsible for manipulating and observing the seedlings the other should observe and record the data in the table You and your partner MUST put on the green filter goggles in order to see the fluorescence properly Hold the seedling by the root or just above where the leaves come out of the stem Holding the seedling close to the light source will give the highest fluorescence if the fluorescence is present Once a seedling has been observed for BOTH the presence absence of trichomes and for fluorescence and the data recorded it may be placed in the waste dish near the blue light source 4 When your group is done observing your seedlings under both conditions enter your data in Table 1 and then share your group data with the class Table 1 Phenotype Number of Expected Page 7 of 10 Seedlings Group Class Seedlings Group Class Trichomes Fluorescent Glabrous Fluorescent Trichomes Non fluorescent Glabrous Non fluorescent Total Total 16 Total 16 5 To calculate the expected number of each phenotype use the phenotype numbers you got from doing your Punnett square last week remember 9 3 3 1 Divide the total number of seedlings group and class by 16 then multiply that value by the expected phenotypic ratio for each phenotype 6 Evaluate your observed vs expected Do they agree If not why might they not 7 Were the results from your group substantially different from the total class data Why Lab Activity 2 2 Heredity in a Dihybrid Cross Using a Simulation Your TA will assign you one or more sets of twenty five seedlings to examine during the lab period These sets taken together represent the F2 population Each set is a two page pdf file The first page shows the seedlings under white light so that the seedlings can be scored for trichomes vs trichomes glabrous The second page is a simulated blue light view in which seedlings can be scored for presence of gfp seedlings are green fluorescing or absence of gfp seedlings are gray not fluorescing The seedlings are shown in the same positions on each of the two pages allowing you to score each seedling for both traits This corresponds to Page 8 of 10
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