Question

R II gene of $T^4$ phage which are neutral at this locus do not cause lysis of K strain of Escherichia coll. If two strains (IR II and $rii^*$) are mixed and then allowed to infect E. coli. It causes lysis. The correct explanation for this is
A) They belong to the same cistron.
B) They belong to two different cistrons.
C) They get reverted to the wild.
D) They get transformed to lytic strains.

Answer 1

Virus of Escherichia coli T4 bacteriophages are bacteria-infecting bacteriophages that infect Escherichia coli bacteria. It is a double-stranded DNA virus belonging to the Tevenvirinae subfamily of the Myoviridae family. T4 can only go through the lytic lifetime, not the lysogenic lifespan.

Complete answer:
Bacteriophages are obligate intracellular parasites that proliferate inside the host cell and are released when the host is destroyed by lysis. The phage T4 genome sequence is 168,903 base pairs long and encodes around 300 gene products. The term "cistron" is a synonym for "gene." The term cistron refers to the fact that genes behave in a certain way in a cis-trans test; distinct places (or loci) within a genome are cistronic.

A cistron is a functional unit of a gene that passes the cis-trans complementation test; each gene has many cistrons. As a result, each cistron codes for a portion of the polypeptide, and the entire polypeptide is made up of all the cistrons in a gene. Different genes, not parts of the same genes, determine lysis and lysogeny.

The transfer of genetic material from one bacterial strain to another without making physical touch is known as transformation. The transfer of genetic material from lytic strain to neutral strain causes the transformation of a neutral strain to lytic strain. Lysis is caused by the mutant strain, rii, as stated in the question. As a result, option D is the proper response.

T-even phages are the most researched model organisms, with research dating back to the 1940s and continuing now. Simple model organisms with as few as five genes are frequently required.

Thus the correct answer is option ‘D’.

Note: Seymour Benzer invented the word cistron in his article The elementary units of heredity. The terms cistron and gene were developed before advances in biology showed that the notions they allude to are almost identical. Many synonyms in the life sciences can be traced back to similar historical naming practises.