Book Viewer

Short Contents | Full Contents | Other books @ NCBI

Modern Genetic Analysis Answers to Selected Problems
Chapter 11*

2.

In pulsed field gel electrophoresis, chromosome-sized pieces of DNA move through a gel. Unless the overall size of a chromosome is changed, it should always migrate to the same relative position.

a. Seven bands identical with wild type.
b. Seven bands identical with wild type.
c. The largest and smallest bands would be expected to disappear. Two new intermediate bands would appear, unless they happened to comigrate with one of the other five wild-type bands.
d. One band would be larger than expected and one would be smaller than expected, compared with the wild type.
e. Seven bands identical with wild type.
f. Seven bands.
g. The largest wild-type band would be missing and an even larger new band would be present.
See question

6. | One approach would be to "knock out" wild-type function and then observe the phenotype. To do this, follow the one-step protocol described for Figure 11-4. Insert a selectable gene into the cloned gene of interest. Linearize the plasmid and use it for transformation of yeast cells. Select for the selectable gene. Another possibility is site-directed mutagenesis (p. 342). See question

7. | After electrophoresis, Southern blot the gel and probe with radioactive copies of the cloned gene. See question

9. | a. Let B = bent tail, b = normal tail. The two genes are linked with 40 m.u. between them. b. The original cross is Br2 / br1 × br1 / br1. The wild-type progeny for tail conformation are See question

10.

a. 1:A1, B2, recombinant

2:A2, B1, recombinant

3:A1, B1, parental

4:A2, B2, parental

b.
See question

12.

a. Recall that yeast plasmid vectors can exist free in the cytoplasm, producing multiple copies that are distributed randomly to daughter cells, or they can be integrated into yeast chromosomes, in which case they replicate with the host chromosome and are distributed as any other yeast gene during mitosis and meiosis.

YP1 produces 100 percent leu+ progeny, suggesting that the leu+ gene is not integrated into a chromosome and that enough copies exist of the plasmid so that all progeny obtained at least one copy.

YP2 produces 50 percent leu+ progeny, which is indicative of orderly distribution and suggests that the leu+ gene is integrated into a yeast chromosome.

b. The "insert," which is not cut with the enzyme, is the leu+ gene inserted into the plasmid.

After digestion, electrophoresis, blotting, and probing, YP1 will produce one band that is somewhat heavier than the plasmid without an insert (that is, it migrates less distance than the plasmid during electrophoresis). YP2 will produce two bands that contain a part of the integrated plasmid, plus genomic DNA. The location of these bands relative to the plasmid cannot be predicted.

See question

© 1999 by W. H. Freeman and Company. All rights reserved.