Answer:

Genetic engineering is a technique that involves altering the genetic material of an organism. It has revolutionized the field of biotechnology, allowing scientists to produce human proteins in bacteria. This is possible due to several factors, one of which is the universality of the genetic code.

Genetic Code:
The genetic code is a set of rules that determines how the genetic information in DNA or RNA is translated into proteins. It is universal, meaning that the same genetic code is used by all living organisms. This universality allows scientists to transfer genetic information from one organism to another, such as from humans to bacteria.

Gene Regulation:
Gene regulation refers to the mechanisms by which genes are turned on or off, controlling the production of proteins. While the mechanisms of gene regulation can vary between different organisms, the basic principles are conserved across species. Therefore, it is possible to engineer bacteria to produce human proteins by introducing the corresponding human genes and ensuring that the appropriate regulatory elements are present.

Replication of Human Chromosomes in Bacterial Cells:
Human chromosomes cannot replicate in bacterial cells. Bacterial cells have their own machinery for DNA replication, which is specific to their own genetic material. However, genetic engineering techniques allow scientists to isolate and manipulate specific genes from human chromosomes and insert them into bacterial cells.

RNA Splicing:
RNA splicing is a process by which non-coding regions, called introns, are removed from the pre-mRNA molecule, and the remaining coding regions, called exons, are joined together. This process is essential for the production of functional mRNA molecules that can be translated into proteins. While RNA splicing occurs in eukaryotic cells, including human cells, it does not occur in bacteria. Therefore, bacterial cells do not have the ability to undertake RNA splicing to produce functional human proteins.

In conclusion, the correct answer is option D: Genetic code is universal. The universality of the genetic code allows scientists to transfer genetic information from humans to bacteria, enabling the production of human proteins in bacteria through genetic engineering.