Question

A nucleic acid probe might be used to:
A) insert genes into a host cell.
B) make DNA for gene cloning.
C) splice pieces of DNA.
D) identify complementary segments present in the nucleic acid sequence.

Answer 1

Hint: A probe is a single-stranded sequence of RNA or DNA used to search for its complementary sequence in a sample genome. The probe is a stretch of oligonucleotides of RNA or DNA usually containing 15-20 nucleotides. The probes can be composed of either RNA or DNA, and they range in length from short oligonucleotides to multigenic chromosomal segments cloned into bacteria (so-called BACs or bacterial artificial chromosomes). Probes are being used to identify a particular DNA fragment in qPCR.
Complete Step-by-step answer:
A probe is used in the screening stage. If a probe is added to a mixture of various pieces of DNA (e.g. restriction fragments). It will anneal (base pair) with any lengths of DNA that contain the complementary sequence. Then these fragments will be labelled and will stand out from the rest of the DNA.
Nucleic acid probes are based on the recognition of unique nucleotide sequences within the RNA or DNA of a microorganism; these unique nucleotide 'signatures' are substitutes for the presence of the organism itself. This affinity and complementary sequence allow binding to certain regions of a target sequence of nucleotides. Bacterial ribosomes are extremely conserved and important organelles liable for protein synthesis. Nucleic acid probes are used to detect mRNA, and to assess interphase chromosomes in tumour cells.
Therefore the correct answer is Option D.
Note: Probe is a fragment of RNA or DNA used to identify the presence of a certain DNA fragment within a sample. Thus, probes can be used for two kinds of techniques, in hybridization reactions and in qPCR.