Exam 17: Applications of Recombinant DNA Technology and Reverse Genetics

What kind of gene silencing is induced by short double-stranded RNAs?

Agrobacterium tumefaciens is often used in the production of transgenic plants because of its Ti plasmid.This plasmid is usually "disarmed" by deleting its tumor genes along with the genes for producing what products that would have been advantageous to the bacterium?

Hedgehog (Hh),and many other signaling pathways,were originally discovered in Drosophila.Hedgehog was so named because of bristles all over the early embryo,resembling a hedgehog.It works,with other genes,to develop the anterior-posterior axis of the embryo. The mutant develops bristles all over the embryo instead of just in a stripe toward the anterior.Thus Hh is a segment polarity gene.The hedgehog gene family in vertebrates is involved in development of central and peripheral nervous system,skeleton limbs,lungs,skin and germ cells.Shh (Sonic hedgehog)is responsible for major development of brain,spinal cord,and skeleton and is received at the membrane via the patched receptor (PTCH).In the absence of Shh,PTCH inhibits the activity of the pathway,while binding of Shh allows signal transduction to go forward. In humans,holoprosencephaly is a developmental disorder involving incomplete cleavage of the forebrain,leading to the abnormalities of brain and facial structures.From the above,which abnormalities of genes must be involved?

Suppose you have engineered a plasmid vector in order to produce a functional animal protein in E.coli.But the product you collect,while it has the correct amino acid sequence,is in fact nonfunctional.What might you try that would have a greater chance of success?

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 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?

Suppose a gene from a cow is introduced into a frog.This results in a ________ transgene.

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?

To introduce dsRNA into C.elegans,it is enough just to dip the worms into media that includes E.coli containing the dsRNA because

In producing an E.coli plasmid to be an expression vector,an experimenter includes genes for selectable markers,a promoter for the expression of the introduced genes.She uses a cDNA sequence to ensure the insert contains no introns.The gene inserted is transcribed,but not translated.What sequence did she omit from the plasmid?

The reasons for using transposon-based mutagenesis include all of the following except

P element transposition requires the enzyme transposase,which acts at the ends of the P element.To find transposons in a germ line,which of these is best?

In the formation of transgenic animals,DNA is usually inserted into eggs or embryos.If some cells of the embryo do not receive the introduced DNA,the result is an organism with cells of different genotypes;the organism is known as what?

One way to genetically engineer S.cerevisiae is by homologous recombination.If a given sequence is thus introduced and is integrated via two regions of homology,is it more probably introduced as a linear or a circular entity?

When a transgene is used in mice to knock out a specific function,two problems that might occur are the unintended introduction of multiple copies,or abnormal gene expression.The second of these problems is related to

For a transgenic animal line to be produced from a chimera,the transgene must be carried by what?

If recombination results in random integration of a DNA sequence,so that it produces a nonhomologous region,the recombination is ________.

If the process used to investigate a genetic condition begins with knowing a DNA sequence and aims at finding the phenotype it causes,this process is known as ________.

Which of the following is a possible advantage for the environment of having farmers use plants that genetically produce Bt toxin?

In species X,the UUU codon for phenylalanine is used significantly more frequently than other phenylalanine codons,and knowing this allows the scientist to manipulate translation efficiency.This unequal frequency is known as ________.