Exam 16: Forward Genetics and Recombinant Dna Technology

Would it be possible and/or appropriate to design a genetic screen to look for a gene(s)involved in homosexuality?

A researcher wants to mutagenize an organism. He is not in need of a large number of mutants but is more concerned with being able to find and then to amplify the mutated sequence. Which of the following would therefore be more useful?

In TILLING, a population of inbred organisms is mutagenized to saturation. DNA from mutagenized lines is isolated and amplified by PCR. PCR products are denatured and allowed to reanneal and then treated with an endonuclease. Why is the denaturation/re-annealing step important for the detection of mutant alleles?

Why do we so frequently use mutant alleles to determine structure and/or function of the wild type?

Identifying an autosomal recessive mutation in a mutagenic screen in Drosophila requires identification of a mutant in the F₃ generation. If testing for a sex-linked recessive lethal mutation (e.g., cn l + using a balancer chromosome such as cnCyO), in which generation can lines with mutations be identified?

Enhancer trapping might occur if you create a library of insertions bearing enhancer-less GAL4 genes. Their expression will be controlled by __________.

Why is only a fraction of an organism's genes represented in any cDNA library?

Knockout libraries are available already prepared for some organisms such as Drosophila. These libraries are originally made by what method?

Before Muller's discovery that radiation induces mutation, scientists had to work on mutations that were found solely by phenotype differences in natural populations. Which of the features Of Drosophila made it a fortuitous choice for Morgan and his colleagues?

In positional cloning, the researcher begins with a phenotype. To move toward identification of its DNA sequence, she must begin with what step?

What kind of analysis is needed to determine whether two mutations are in the same gene or in different genes?

If a gene in Drosophila is expressed only when an imaginal disc (A)begins to differentiate, it is referred to as a homeotic gene. Recessive mutations in such genes often result in loss of function so that the structure does not develop. If the gene is expressed, but in a different imaginal disc (B), what is the result?

Transgenic fusions between a gene and a reporter are used to determine whether a gene is expressed. Which of these components allows the researcher to work with living specimens, and why?

In an organism, X, it is found to be impossible to generate loss-of-function mutants for most genes. There is an alternative method of introducing random mutations that can later be screened for the gene(s)in question. This can be accomplished by using insertions due to what structures?

In nature, RNAi protects cells against infection by what kind of pathogen?

In reverse genetics, what is the correct order in which the experimenter proceeds?

If an experimenter wants to use the GFP method but needs to detect the presence or absence of several proteins at the same time, he can take advantage of mutational variants of GFP that emit what?

In a given situation, reduced or missing function in gene A results in a viable but noticeable phenotype. The same is true for gene B. However, when both gene A and gene B products are reduced or missing in the same organism, the result is lethality. What is this called?

If you wish to rid an experimental organism of the function of a gene, you can use RNAi. What would you inject into the organism?

If a mutagen such as EMS is used to produce numerous mutagenized cell lines for an organism, PCR can be used to select for a particular gene. However, what feature of this selected sequence is used to find the ones with mutations in that gene?