Worksheet for Morgan/Carter Laboratory #9 Mendelian Genetics II: Drosophila

Transcription

1 Worksheet for Morgan/Carter Laboratory #9 Mendelian Genetics II: Drosophila Ex. 9-1: ESTABLISHING THE ENZYME REACTION CONTROLS Propose a hypothesis about AO activity in flies from vial 1a and flies from vial 1b. Predict the results of the experiment (test) based on your hypothesis (if/then). Why is it necessary to homogenize the flies? Record your results in the table below: Vial 1a (AO present) Vial 1b (AO absent) Fly # Sex (F or M) AO Activity (+/-) Fly # Sex (F or M) AO Activity (+/-) Do your results match your predictions? Does the sex of the fly appear to have an impact on the results of the assay test? Which two characteristics are most useful to your group in determining the sex of the flies? Ex. 9-2: DETERMINING THE PATTERN OF INHERITANCE OF THE ALDOX GENE What is the genotype of the female (maternal parent lacks the enzyme) in our cross? What would be the genotype of the male (paternal parent has the enzyme) in our cross if the gene is not sex-linked?

2 What would be the genotype of the male if the gene is sex-linked? What would be the genotypes of the F 1 progeny if the gene is not sex-linked? What would be the genotypes if the gene is sex-linked? Propose a hypothesis about the inheritance of this gene. Is it sex-linked? According to your hypothesis, what will be the genotypes of the parents? Predict the offspring from the hypothesized parents (hint: use a Punnett square) Record your results in the table below: Positive control: Fly # Sex (F or M) AO Activity (+/-) Fly # Sex (F or M) AO Activity (+/-) What allele appears to be dominant? What evidence of your results above supports your answer? Based on your results, should the aldox gene be written beginning with a capital or lowercase letter?

3 Correctly write the names of the wild-type and mutant alleles. By convention, wild-type alleles are designated with a superscript + after the name (e.g., gene + ). Did you hypothesize that the gene was sex-linked (on a sex chromosome) or autosomal? Describe how your results either support or falsify your hypothesis. Write a statement describing your conclusions from this experiment. Ex. 9-3: DETERMINING PARENTAL GENOTYPES USING EVIDENCE FROM PROGENY Record your results in the table below: Positive control: Fly # AO Activity (+/-) Fly # AO Activity (+/-) Total the number of offspring in each phenotype category below: AO-present AO-absent Your Totals Class Totals Is the trait sex-linked? Which allele is dominant?

4 Using all observations, hypothesize the genotypes of the parent flies, making sure to name the alleles correctly. Predict the results of the experiment (if/then). Complete the chi-square calculations in the table below (optional): Observed Value (o) Expected Value (e) Deviation (o - e) or d Deviation 2 (d 2 ) d 2 /e Chi-square 2 d 2 /e Degrees of freedom (df) Probability (p)* *see a 2 table Do the class results support or falsify your hypothesis? AO Activity (+) AO Activity (-) Does the experiment support or contradict your conclusions concerning the pattern of inheritance derived from Experiment 9.2? Ex. 9-4: MAPPING GENES (optional) Propose a hypothesis about the inheritance of these two genes. Are they inherited linked together or independently of each other? Predict the ratios of phenotypic classes of offspring resulting from the mating described above, and use a Punnett square to illustrate your prediction.

5 Record your results for eye color classification and the spot tests in the table below: Fly # Eye Color AO Activity (+/-) Fly # Eye Color AO Activity (+/-) Total the class data and your data below: red eyes, AO-present red eyes, AO-absent sepia eyes, AO-present sepia eyes, AO-absent Your Totals Class Totals What phenotypic classes were observed in the total class data, and in what approximate ratio?

6 On a separate piece of paper, using class totals, perform the chi-square test to determine if the results support or falsify your hypothesis (see appendix B). Do the data support your predicted results? If the results differ from what was expected, can you suggest an explanation for these differences? What are the recombinant classes of phenotypes for this cross? In your experiment, did recombinant classes exist? If they did, how frequent were they? Do your data suggest that aldox and sepia are on the same chromosome, and if so, how far is the aldox locus from the sepia locus? What would be the exact map position of the aldox locus if the sepia locus is 26.0? Are you sure? REVIEWING YOUR KNOWLEDGE List the most obvious characteristics used to determine the sex of a fruit fly. A fruit fly geneticist discovered a genetic mutation that resulted in pupae and young flies with dark pigment granules in the nuclei and cytoplasm of their fat cells. After studying the inheritance of the mutation, the geneticist named the gene Frd (for Freckled). What does this name tell you about the inheritance of this gene? In another strain of fruit flies, geneticists discovered a mutation producing flies with no gut muscles. They named the gene controlling this phenotype jeb (for jelly belly). What does this tell you about the inheritance of this gene? Is the genetic map or linkage map produced by determining recombination frequencies an actual physical map of the chromosome? Refer to your textbook.