Understanding recombination in bacteria and in viruses that infect bacteria.

A cross is made between Hfr met+ thi+ pur+ X F- met- thi- pur-. Interrupted-mating studies show that met+ enters the recipient last, so met+ exconjugants are selected on medium containing thi and pur only. These exconjugants are tested for the presence of thi+ and pur+. The following numbers of individuals are found with ea ...continues

The definitions of merozygote, recombinant frequency, recessive phenotype and sex chromosome.

Define the following terms: MEROZYGOTE RECOMBINANT FREQUENCY (RF) RECESSIVE PHENOTYPE SEX CHROMOSOME

The definition of a transposable genetic element.

Define transposable genetic element.

Recombination in bacteria is defined.

A particular Hfr strain normally transmits the pro+ marker as the last one during conjugation. In a cross of this strain with an F- strain, some pro+ recombinants are recovered early in the mating process. When these pro+ cells are mixed with F- cells, the majority of the latter are converted to pro+ cells that also carry the ...continues

Understanding recombination in bacteria.

A transformation experiment is performed with a donor strain that is resistant to four drugs: A, B, C, D. The recipient is sensitive to all four drugs. The treated recipient-cell population is divided up and plated on media containing various combinations of the drugs. The results are shown in the table below. Drug # co ...continues

Understanding the DNA structure is achieved.

If you extract the DNA of the coliphate thetaX174, you will find that its composition is 25 percent A, 33 percent T, 24 percent G, and 18 percent C. Does this make sense in terms of Chargaff's rules? How would you interpret this result? How might such a phage replicate its DNA? Ideas are expressed.

DNA structure of viruses and cancer is illustrated.

In mice, there are viruses that are known to cause cancer. You have a pure preparation of virus DNA, a pure preparation of DNA from the chromosomes of mouse cancer cells, and pure DNA from chromosomes of normal mouse cells. Virus DNA will specifically anneal with cancer-cell DNA, but not with normal-cell DNA. I then explore t ...continues

Understanding the DNA structure.

In the harlequin-chromosome technique, you allow THREE rounds of replication in bromodeoxyuridine and then stain the chromosomes. What result do you expect to obtain?

Understanding eukaryotic chromosome mapping techniques.

In haploid yeast, a cross between arg- ad- nic+ leu+ and arg+ ad+ nic- leu- produces haploid sexual spores, and 20 of these are isolated at random. The resulting cultures are tested on various media as shown below (in the table below, + means growth, while - means no growth). (a) What can you say about the linkage arrangement ...continues

Understanding chromosome mapping techniques.

(a) By using the map function, calculate how many real map units are indicated by a recombinant frequency of 20 percent. Remember that a mean of 1 equals 50 real map units. (b) If you obtain an RF value of 45 percent in one experiment, what can you say about linkage? (The actual figures are 58, 52, 47, and 43 out of 200 pro ...continues