To solve this problem, we need to identify which of the given options is not a cloning vector. Let's analyze each option:$\newline \bullet$BAC (Bacterial Artificial Chromosome):$\newline$ - BACs are large plasmid vectors used to clone DNA fragments in bacterial cells.$\newline$ - They are commonly used in genomic library construction and sequencing projects.$\newline$ - Therefore, BAC is a cloning vector.$\newline \bullet$YAC (Yeast Artificial Chromosome):$\newline$ - YACs are vectors used to clone large DNA fragments in yeast cells.$\newline$ - They are useful for studying eukaryotic chromosomes and gene mapping.$\newline$ - Therefore, YAC is a cloning vector.$\newline \bullet$pBR322:$\newline$ - pBR322 is a well-known plasmid vector used in bacterial cloning.$\newline$ - It contains antibiotic resistance genes and is used for cloning small DNA fragments.$\newline$ - Therefore, pBR322 is a cloning vector.$\newline \bullet$Probe:$\newline$ - A probe is a fragment of DNA or RNA used to detect the presence of complementary sequences by hybridization.$\newline$ - Probes are not used for cloning; they are used for detection and identification purposes.$\newline$ - Therefore, a probe is not a cloning vector.$\newline$Based on the analysis, the correct answer is Option 4: Probe, which is not a cloning vector.