Recombinant DNA Technology
Some genetic diseases cannot be diagnosed by changes in restriction sites. Some of these can be detected by allele-specific oligonucleotide probes. These are

PCR-amplified variable numbers of tandem repeats (VNTRs)
mutagenized copies of a gene
short sequences that will hybridize only to a specific base sequence
copies of the gene with an altered sequence so that a restriction site is inserted

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Recombinant DNA Technology
The order for the construction of a cDNA fragment from mRNA is to

bind oligo-dT, treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dC, treat with DNA polymerase
treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dC, treat with DNA polymerase and bind oligo-dT
digest with RNase, add G residues to the 3' end, treat with reverse transcriptase, add G residues to the 3' end and treat with DNA polymerase
bind oligo-dC, treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dT and treat with DNA polymerase

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Recombinant DNA Technology
An expression vector

All of these
always contains an origin of replication
always contains DNA segments for the regulation of mRNA production
usually contains a gene that confers antibiotic resistance to the bacterial host

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Recombinant DNA Technology
A human cDNA library

cannot be used to obtain human genes because it would be radioactive
None of these
contains DNA for virtually all of the human proteins in vectors
contains DNA for specific human proteins

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