In specialized transduction, $\lambda$ phased transduces………...genes of Escherichia coli.
A)trp
B)gal
C)bio
D)All of the above

Hint: Transduction is a process when DNA is transferred from one bacteria to another with the help of a virus. The transaction process does not require any physical contact between the cell who is giving the DNA and the cell who is receiving the DNA. It is the most usual tool used by many molecular biologists to introduce the foreign gene into a host cell genome.

Complete answer:
-When a restricted set of bacterial genes is transferred to another bacterium then the process is known as specialized transduction. In this specialized transducing phage bear a specific part of the bacterial chromosome.
-Most-studied example of specialized transduction is the lambda phage. They usually inject their genome into the host chromosome at a very specific location known as attachment site or att site.
-The two cos sites are present on the lambda phage that helps them to ligate. When the lambda phage introduces its DNA into the bacteria, it leads to the crystallization of the phage due to cos sites. All the genes are transduced due to the location of the lambda phage in the bacterial genome.
-Phage lambda is a very good example of a specialized transducing phage in E-coli bacteria. The lambda phage injects its DNA in a very precise manner between the operons encoding enzymes which are in charge of galactose (gal) and biotin (bio) utilization of the E.coli chromosomes.
-In specialized transduction, there is site-specific recombination and transductants keep the recipient copy of the transduced genes and become $\lambda$ lysogens.
-Same with, the trp genes which is transduced due to site-specific recombination in specialized transduction.

Additional Information: -Whenever the temperate bacteriophages involved specialized transduction occurs. The temperate phage reproduces by both the lysogenic or lytic cycle.
-The temperate phage injects its DNA into the host bacterial genome during the lysogenic cycle. Phage DNA is known as a prophage.
-The integration is very specific in some temperate phages.
Example - $\lambda$ always enters between the gal region and the bioregion of the host chromosome.
So, the correct answer is,” all of the above”

Note: -The process of transaction is very important in molecular biology used to study bacteria.
-Its major use is - in genetic mapping, site-directed mutagenesis, and strain construction.
-The small length of the transduced fragment always allows the recombination of a small region of interest.