Viruses might be an example of what is called an evolutionary stable strategy. Describe the
adaptive advantages of the viral \"way of life\" and how selection contributes to this stability.
How is a repressible operon different than an inducible operon?
Solution
1. Viruses are acellular, microscopic and obligate parasites that require a host for their survival.
Viruses can infect plants, animals and bacteria too. The viruses that infect bacteria are called
bacteriophages. The diagram shows the bacteriophage (T7), which is in tadpole shape. The
tobacco mosaic virus (TMV) shown in the diagram infects tobacco plants is a rod shaped virus.
The human immune deficiency virus (HIV) is in spherical shape. Most of the plant viruses
contain RNA as genetic material with few exception of having DNA. The bacteriophages contain
DNA with few exceptions. The viruses that infect animals and humans generally have DNA but
the HIV contains RNA.Though, the viruses have different forms and shapes, all viruses contain a
nucleic acid either DNA or RNA, which is surrounded by a protein capsid or coat or shell. Some
of the viruses have surface glycoproteins that act as antigens and elicit immune response in host.
The immune system of the host try to eliminate them by producing antibiotics or treatment with
antibiotics but the viruses can change their antigentic structures through mutations, genetic shift
and drift and are able to cause infection in same host. Thus, viruses have new strategies always
for their evolution and have adoptations and advantages to win over host to maintain a stable
evolutioary strategy.
2. Genes in prokaryotes are regulated in clusters called operons. An operon contains a set of
genes consisting of promoter, operator, and a cluster of structural genes that produce products
having same function. The operon can be upregulated or down regulated to control its
expression.
Repressor is a protein that inhibits the transcription of genes when it is bound to specific DNA
sequences or near promoter. The repressor is bound at the operator to inhibit the transcription.
For example, in tryptophan operon when tryptophan is available in excess amounts, the repressor
bind to operator to turn off the transcription.
In inducible operon, a small molecule called inducer binds to operator to turn on the transcription
of the genes. In absence of inducer, repressor binds to operatyor and inhibits transcription. In Lac
operon, lactose acts as inducer that brings about confirmational change in promoter and thereby
RNA polymerase binds to it to initiate transcription..
Viruses might be an example of what is called an evolutionary stable .pdf
1. Viruses might be an example of what is called an evolutionary stable strategy. Describe the
adaptive advantages of the viral "way of life" and how selection contributes to this stability.
How is a repressible operon different than an inducible operon?
Solution
1. Viruses are acellular, microscopic and obligate parasites that require a host for their survival.
Viruses can infect plants, animals and bacteria too. The viruses that infect bacteria are called
bacteriophages. The diagram shows the bacteriophage (T7), which is in tadpole shape. The
tobacco mosaic virus (TMV) shown in the diagram infects tobacco plants is a rod shaped virus.
The human immune deficiency virus (HIV) is in spherical shape. Most of the plant viruses
contain RNA as genetic material with few exception of having DNA. The bacteriophages contain
DNA with few exceptions. The viruses that infect animals and humans generally have DNA but
the HIV contains RNA.Though, the viruses have different forms and shapes, all viruses contain a
nucleic acid either DNA or RNA, which is surrounded by a protein capsid or coat or shell. Some
of the viruses have surface glycoproteins that act as antigens and elicit immune response in host.
The immune system of the host try to eliminate them by producing antibiotics or treatment with
antibiotics but the viruses can change their antigentic structures through mutations, genetic shift
and drift and are able to cause infection in same host. Thus, viruses have new strategies always
for their evolution and have adoptations and advantages to win over host to maintain a stable
evolutioary strategy.
2. Genes in prokaryotes are regulated in clusters called operons. An operon contains a set of
genes consisting of promoter, operator, and a cluster of structural genes that produce products
having same function. The operon can be upregulated or down regulated to control its
expression.
Repressor is a protein that inhibits the transcription of genes when it is bound to specific DNA
sequences or near promoter. The repressor is bound at the operator to inhibit the transcription.
For example, in tryptophan operon when tryptophan is available in excess amounts, the repressor
bind to operator to turn off the transcription.
In inducible operon, a small molecule called inducer binds to operator to turn on the transcription
of the genes. In absence of inducer, repressor binds to operatyor and inhibits transcription. In Lac
operon, lactose acts as inducer that brings about confirmational change in promoter and thereby
RNA polymerase binds to it to initiate transcription.
