2. Analysis of unordered yeast tetrads from the cross of a haploid strain with genotype + + + with a strain of genotype a b c yielded the following data. The genotypes of four spores from the same tetrad are listed on each horizontal line. Tetrad Class Spores Number of Asci 1. a b c a b c + + + + + + 36 2. a b c a + c + b + + + + 14 3. a + + a + + + b c + b c 32 4. a b + a + + + b c + + c 16 5. a b + a b + + + c + + c 2 a. Which of these genes are linked, and what is the map distance between them? Show your work. (4 pts) b. Draw a map that illustrates the relative locations of these three genes and their respective centromeres. (2 pts)
Added by Mar P.
Close
Step 1
Draw a map that illustrates the relative locations of these three genes and their respective centromeres. Show more…
Show all steps
Your feedback will help us improve your experience
Sri K and 101 other Biology educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
A yeast geneticist irradiates haploid cells of a strain that is an adenine-requiring auxotrophic mutant, caused by mutation of the gene ade1. Millions of the irradiated cells are plated on minimal medium, and a small number of cells divide and produce prototrophic colonies. These colonies are crossed individually with a wildtype strain. Two types of results are obtained:(1) prototroph Ă— wild type : progeny all prototrophic(2) prototroph Ă— wild type : progeny 75% prototrophic, 25% adenine-requiring auxotrophsa. Explain the difference between these two types of results.b. Write the genotypes of the prototrophs in each case.c. What progeny phenotypes and ratios do you predict from crossing a prototroph of type 2 by the original ade1auxotroph?
Katlin K.
Imagine that you have done a cross between two strains of yeast, one of which has the genotype $A B C$ and the other $a b c,$ where the letters refer to three rather closely linked genes in the order given. You examine many tetrads resulting from this cross, and you find two that do not contain the expected two $B$ and two $b$ spores. In tetrad $I$, the spores are $A B C$, $A$ $B C, a B c,$ and $a b c .$ In tetrad II, the spores are $A B$ $C, A b c, a b C,$ and $a b c .$ How have these unusual tetrads arisen?
For an experiment with haploid yeast, you have two different cultures. Each will grow on minimal medium to which arginine has been added, but neither will grow on minimal medium alone. (Minimal medium is inorganic salts plus sugar.) Using appropriate methods, you induce the two cultures to mate. The diploid cells then divide meiotically and form unordered tetrads. Some of the ascospores will grow on minimal medium. You classify a large number of these tetrads for the phenotypes ARG(arginine requiring) and $\mathrm{ARG}^{+}$ (arginine independent) and record the following data: $$\begin{array}{cc} \begin{array}{c}\text { Segregation } \\\text { of ARG }^{-}: \mathrm{ARG}^{+}\end{array} & \begin{array}{c}\text { Frequency } \\(\%)\end{array} \\\hline 4: 0 & 40 \\3: 1 & 20 \\2: 2 & 40 \\\hline\end{array}$$ a. Using symbols of your own choosing, assign genotypes to the two parental cultures. For each of the three kinds of segregation, assign genotypes to the segregants. b. If there is more than one locus governing arginine requirement, are these loci linked?
Recommended Textbooks
Biology for AP Courses
Objective Biology for NEET
Introduction to General, Organic and Biochemistry
Transcript
18,000,000+
Students on Numerade
Trusted by students at 8,000+ universities
Watch the video solution with this free unlock.
EMAIL
PASSWORD