What is the major difference between a hub and switch, which one is more efficient at routing traffic, and which is preferable in larger network configurations? Solution The term\' Hub\' usually refers to a piece of network equipment which connects personal computers together.This type of device carry forwards the information it receives so that it\'s ports receive the information.Hubs repeat everything they receive and can be used to extend the network.This can cause unnecessary traffic being send to devices in a network.This kind of repeating is not a problem in the case of smaller networks but for larger traffic it becomes a problem so we need to implement another network equipment called switch. Switches control the netwok traffic by containing the address information of each packet and it checks to which ports it has to send packets and sends on packets to relevant ports only.This allows simultaneous communication across switch by improving bandwidth utilisation. Hubs are used in smaller networks and are used to extend network by providing more number of ports and switches divide the network into smaller and less blocked sections. Finally switches are more efficient at routing traffic..

1. What is the role of capsid and nucleocapsid proteins during the life cycle of RNA viruses?
Solution
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made
of protein called protomers. The observable 3-dimensional morphological subunits, which may
or may not correspond to individual proteins, are called capsomeres. The capsid encloses the
genetic material of the virus. with its enclosed nucleic acid, it is called the nucleocapsid. This
shell is composed of protein organized in subunits known as capsomers. They are closely
associated with the nucleic acid and reflect its configuration, either a rod-shaped helix or a
polygon-shaped sphere. The capsid has three functions: 1) it protects the nucleic acid from
digestion by enzymes, 2) contains special sites on its surface that allow the virion to attach to a
host cell, and 3) provides proteins that enable the virion to penetrate the host cell membrane and,
in some cases, to inject the infectious nucleic acid into the cell's cytoplasm. Under the right
conditions, viral RNA in a liquid suspension of protein molecules will self-assemble a capsid to
become a functional and infectious virus.
HIV-1 nucleocapsid protein (NC) is a small basic protein generated by the cleavage of the Gag
structural polyprotein precusor by the viral protease during virus assembly in the infected cell.
HIV-1 NC possesses two copies of a highly conserved CCHC zinc finger (ZnF), flanked by basic
residues. HIV-1 NC and more generally retroviral NC proteins are nucleic acid binding proteins
possessing potent nucleic acid condensing and chaperoning activities. As such NC protein drives
critical structural rearrangements of the genomic RNA, notably RNA dimerization in the course
of virus assembly and viral nucleic acid annealing required for genomic RNA replication by the
viral reverse transcriptase (RT). Here we review the relationships between the 3D structure of
HIV-1 NC, notably the central globular domain encompassing the two zinc fingers and the basic
linker and NC functions in the early and late phases of virus replication. One of the salient
feature of the NC central globular domain is an hydrophobic plateau which appears to orchestrate
the NC functions, such as chaperoning the conversion of the genomic RNA into viral DNA by
RT during the early phase, and driving the selection and dimerization of the genomic RNA at the
initial stage of viral particle assembly. This ensures a bona fide trafficking of early GagNC-
genomic RNA complexes to the plasma membrane of the infected cell and ultimately virion
formation and budding.