Validation methods for recombinant clones:

• Colony hybridization uses sequence-specific labeled nucleic acid probes to directly identify colonies containing the insert of interest.
• Colony PCR amplifies the cloned insert directly from bacterial lysate using vector- or gene-specific primers.
• Selection media (e.g., antibiotic-containing plates or blue-white screening) selects and screens recombinant transformants.
• Growing transformants at low temperature does not differentiate between recombinant and non-recombinant or vector-only clones, and is not a molecular screening technique.

Application of labeled nucleic acid probes:

• Southern hybridization, Northern hybridization, and Colony hybridization fundamentally rely on labeled single-stranded DNA/RNA probes that hybridize to complementary immobilized target sequences on nitrocellulose/nylon membranes.
• Conventional RT-PCR (Reverse Transcription-Polymerase Chain Reaction) utilizes sequence-specific oligonucleotide primers to enzymatically synthesize and amplify cDNA by DNA polymerase, without requiring labeled hybridization probes.

Thomas Hunt Morgan's linkage and crossing over experiments in Drosophila melanogaster:

• Grey body ($b^+$) is dominant over black body ($b$), and normal wings ($vg^+$) are dominant over vestigial wings ($vg$). Both loci reside on chromosome 2.
• Parents: Grey normal ($b^+ vg^+ / b^+ vg^+$) $\times$ Black vestigial ($b\, vg / b\, vg$).
• In a testcross of female $F_1$ dihybrids ($b^+ vg^+ / b\, vg$) with double recessive black vestigial males ($b\, vg / b\, vg$), the non-parental recombinant offspring—grey vestigial ($b^+ vg / b\, vg$) and black normal ($b\, vg^+ / b\, vg$)—arise exclusively due to crossing over and recombination between linked genes.
• Because the genes reside on the same chromosome (linked) and produce non-parental recombinant types via crossing over, statements (A) and (C) only are true.

Primary biological databases and content types:

• GenBank (NCBI, USA), EMBL-EBI (Europe), and DDBJ (Japan) constitute the International Nucleotide Sequence Database Collaboration (INSDC), exclusively storing primary nucleotide and nucleic acid sequence data.
• SWISS-PROT (now part of UniProtKB/Swiss-Prot) is a curated, non-redundant protein sequence and function database, storing amino acid sequence records, not nucleic acid data.