Answer:
Bacteriophages (phages) are viruses that infect only bacteria and do not infect mammalian or plant cells. Phages are ubiquitous in the environment. Phages or bacteriophages were chosen as a model system for their simplicity, as they only contained protein-coated nucleic acid. Alfred D. Hershey and Martha Chase (who were part of the bacteriophage group) in 1952 studying the infection of the bacterium Escherichia coli by the T2 phage show that the information definitely resides in the DNA. They used phage with either [32P] -labeled DNA or [35S] -labeled proteins to infect the bacteria. Immediately afterwards, they centrifuged the sample so that the infected bacteria remain in the pellet and the virus capsids (proteins) remain in the supernatant. [35S] is found in the supernatant, whereas [32P] is found in bacteria. After one cycle of infection, it was observed that when phage labeled in the [35S] proteins were used, only 1% of the radioactivity was incorporated into the progeny. But when phages were [32P] labeled, more than 30% of the radioactivity was in the progeny. They showed directly that what is transmitted from one progeny to another is the DNA and not the proteins, despite having first "diluted" in a bacterium.
Explanation:
Bacteriophages are viruses that infect bacteria in a specific way. Bacteriophages, like other known viruses, are found in an intermediate zone between living organisms and inert matter. Bacteriophages bind to the host pathogenic bacterium, introduce their genetic material, replicate inside it and destroy it. Hersey, along with his assistant Martha Chase, used phages because they knew that T2 phages were made up of 50% proteins and 50% nucleic acids and that phages entered bacteria and reproduced. As the progeny carried the same infection traits, the genetic material of this had to be transmitted to the offspring, but the mechanism was unknown. These scientists carried out an experimental work with the T2 virus, a bacteriophage that infects the bacterium Escherichia coli, which it reproduces by attaching itself to the outer wall of the bacterium, injecting its DNA into it where it replicates and directs the synthesis of the phage's own proteins. Phage DNA is encapsulated within proteins and produces phages, which lyse or disrupt the cell and release phage from progeny. They infected a culture of bacteria with radioactively labeled phages: the protein coat with sulfur (35S) and its DNA with phosphorus (32P). After infection, they separated the phages from the bacteria by violent shaking using a mixer (hence the name of the experiment). By centrifugation the much smaller phages remained in the supernatant and the much larger bacteria in the pellet. 85% of the radioactivity corresponding to DNA appeared in the pellet and 82% of the protein in the supernatant. This result supported the idea that DNA was the only component of the bacteriophage that penetrated the interior of the bacteria and, having the ability to form new phages, constituted the genetic material.
A mother's diet before conception can permanently affect how her child's genes function, according to a study published in Nature Communications. A 2003 study found that a female mouse's diet can change her offspring's coat color by permanently modifying DNA methylation.
Rabbit ear size tends to decrease as latitude increases. this is an example of a cline
.
A cline can be described as a change of the biological trait of a species across its geographical range. A cline can be genetic for example, change in the allele frequency, or phenotypic (change in body size). The change can be shown as continuous gradation, or it can be more abrupt from one geographic region to the next.
The options of the given question are:
method for DNA delivery
gene construct
efficient selection strategy
tissue culture system
Answer: Tissue culture system.
Explanation:
The role of tissue culture system is not much in case of the transgenic plant. The method of DNA delivery, efficient selection strategy and gene construct are involved in the plant transformation.
But plant tissue culture is not directly involved in the plant transformation. The plant tissue culture is the collection of the techniques which is used to maintain the growth of the plant cells and so it does not plays any important role in plant transformation.
The plant transformation is the introduction of the desired characters into the plant and then the growth of transformed plant takes place in the culture medium. This has no role in the plant transformation or has less role.
