A molecular biologist used a retroviral vector to introduce a gene coding for a certain human enzyme into mouse cells. One cell line was isolated that was able to make the human enzyme, but it had lost the ability to express an endogenous, normally expressed gene in the process. What is the best explanation for these results?

Bacteria use restriction enzymes to __________.

Which of the following enzymes could seal a nick in one strand of a double-stranded DNA molecule by creating a sugar-phosphate bond between the adjacent, unjoined nucleotides?

The efficiency of cloning, and the ability to generate healthy cloned animals, has been largely hampered by the difficulty of __________.

In genetic engineering, the highly active plasmid from Agrobacterium tumefaciens is used to __________.

In DNA technology, the term vector can refer toa. the enzyme that cuts DNA into restriction fragments.b. the sticky end of a DNA fragment.c. a SNP marker.d. a plasmid used to transfer DNA into a living cell.

Which of the following is true of a codon? (A) It never codes for the same amino acid as another codon. (B) It can code for more than one amino acid. (C) It can be either in DNA or in RNA (D) It is the basic unit of protein structure

Which of the following would be considered a transgenic organism?a. a bacterium that has received genes via conjugationb. a human given a corrected human blood-clotting genec. a fern grown in cell culture from a single fern root celld. a rat with rabbit hemoglobin genes

Which of the following is true of cDNA produced using human brain tissue as the starting material? (A) The procedure to make it requires amplification by the polymerase chain reaction. (B) It is produced from pre-mRNA using reverse transcriptase. (C) It can be labeled and used as a probe to detect genes expressed in the brain. (D) It includes the introns of the pre-mRNA.