Avery, McCleod, and McCarty provided evidence that the substance responsible for converting a nonpathogenic form of pneumococci into a pathogenic form is DNA, not proteins or other cellular constituents. Explain with the help of diagrams.
·
Introduction
by viral infection is one possible route. RNA retroviruses can accidentally
incorporate RNA originating from mRNA for a control gene. If this RNA leads
to the production of an oncogenic product then a tumour will result.
·
The
normal cellular equivalent is called a proto-oncogene. Examples of oncogenes
include those derived from ras (v-ras) and from erb (v-erb).
·
Oncogenes
can also be acquired via changes in the cellular proto-oncogene so that it
becomes an oncogene directly. This can occur by mutation of chromosomal
rearrangement.
· Sometimes the normal proto-oncogene becomes overproduced by being under the control of an inappropriate promoter/enhancer and this leads to oncogenesis.
Can all human proteins be produced relatively easily using bacteria once we have isolated the human gene in cDNA form? Explain.
If you were attempting to produce a human protein using recombinant techniques in a bacterial system would you use genomic DNA? Why?
Translation is the mechanism of protein synthesis. Some newly synthesised proteins are directly secreted out through ER. How are these proteins secreted through the ER membrane?
How many high-energy phosphates does it require for the direct synthesis of a protein of 200 amino acids in length? Do not include the cost of making the components required, such as amino acids, nor the cost of making the protein synthetic apparatus.
Would you expect tRNAs within a given organism to be the same size or can they vary? Why?
Would
you expect the insertion of a single base into a gene or changing a single
base within a gene to have more effect? Why?
Newly
synthesised proteins during translation are prevented from folding until it
reaches its destination. What mechanism prevents these newly synthesised
proteins from folding and getting in to the functional 3D form. Explain.
How does protein synthesis in eukaryotes differ from that of prokaryotes? Explain.
How is fidelity of translation achieved? Explain the possible mechanism to incorporate the correct amino acids as per the codon.
Accurate translation requires that the correct aminoacyl tRNA bind to the A site. It appears that tRNAs arrive randomly and incorrect ones do not bind long enough for peptide bond formation to occur.
Peptide synthesis does not occur until the GTP on the EF-Tu is hydrolysed, which permits the EF-Tu to dissociate. The pause in GTP hydrolysis permits incorrect aminoacyl-tRNAs to dissociate.
Explain
the various steps in the molecular mechanism of peptide elongation during
protein translation.
Explain
the various molecular events that leads to the initiation of translation in E.coli.
Ribosomes
are considered as the platform of protein translation. Explain how the
structure and chemical composition of ribosomes are related to its
function.
The
transfer of the exact amino acids to the site of protein synthesis is the
function of tRNA. The attachment of the amino acid top the respective tRNA
is known as ‘charging of tRNA’ and the charged tRNA is known as amino
acyl tRNA. Explain the molecular mechanisms that leads to the formation of
aminoacyl tRNA. How the amino acids recognise its respective tRNA during the
process of ‘charging’.
The
effect of certain point mutations can be nullified by the mechanism of
wobble pairing. Explain.
Explain
the secondary structure of transfer RNA with a neatly drawn diagram.
Draw the genetic code and give the names of amino acids, which has one and two codons. Which are the stop codons?
Compare
protein synthesis in mitochondria and in prokaryotes.
Describe
the steps involved in the initiation of protein synthesis in bacteria.
Explain
why protein synthesis is a target for many inhibitors and provide at least
three examples of inhibitors and their site of action.
Histone
genes have the following characteristics: they do not have introns, are
arranged in multiple tandem arrays each with one copy of the five histone
genes and do not have poly A tails. What explanation can be suggested for
these features?
What
position you can give for ribozymes in the evolution of DNA as the genetic
material? Explain.
Describe
the mechanism of gene transcription in eukaryotes, showing how the
production of the final mRNA differs from that which occurs in prokaryotes.
What
is meant by splicing? Alternative
splicing can lead to the production of two (or more) proteins for the price
of one gene. Explain.
Describe
transcription processes in mitochondria, emphasizing how these differ from
nuclear processes.
What
are the factors that control mRNA stability and control of gene expression.
Give
a detailed account of various types of eukaryotic promoters and its role in
the transcriptional regulations.
What
are the arguments put forward for the view that the first living material
was RNA based?
Why
are there multiple genes for rRNA but only single copy genes for ribosomal
proteins?
RNA
polymerase has no proofreading activity but DNA polymerase does. Why the
difference? Explain
What
are Zinc finger proteins? Explain its importance in the gene regulation.
Describe
the structure of RNA and explain how it differs from DNA.
Define
the terms transcription, translation, template strand and coding strand in
the context of molecular biology.
The following is the sequence of an mRNA. Give the sequence of the coding strand or sense strand of its gene. AUC GCC UAG AGC CCC UUC CCA AGG CGC CUG GGC UGA AAA AAA
Explain the mechanism of attenuation.
Using
the tryptophan operon (or a similar operon) as an example compare and
contrast control of a repressible operon with that of an inducible operon.
Explain
mechanisms of termination of transcription in prokaryotes.
What
is sigma factor? Provide examples of different forms of sigma factor and
their biological roles.
What
are the various types of DNA binding proteins involved in the regulation
gene expression in both eukaryotes and prokaryotes?
What is meant by Shine–Delgarno sequence ? Where it is
located? Explain its role in gene expression.
What
is the possible relevance of the existence of telomeres and the occurrence
of telomerase to profound biological events such as cancer and ageing?
Cells
treated with UV light have a higher survival rate if they are exposed to
light immediately afterwards? Explain.
RNA
synthesis does not involve proof reading as in the case DNA synthesis.Does
the use of an RNA primer for DNA synthesis affect the accuracy of DNA
replication in E. coli? Explain.
In
many strains of bacteria the doubling time is less than the time taken to
synthesise a complete copy of the DNA. How might the bacteria cope with this
situation? Does a similar situation arise in animals?
Explain
the molecular mechanism of homologous recombination E.coli.
What
are transposons or mobile genes? Explain its nature, different classes and
its biological significance.
The genomes of some retroviruses have homology with that
human DNA sequences. Explain the possible origin of retroviruses on the
basis of transposons.
Transposons are mutagens. Explain this statement with the help of evidences.
Explain how telomerase acts to overcome the problem associated with the replication of the ends of DNA.
List differences between eukaryote and prokaryote DNA synthesis.
Explain
the meaning of ‘semiconservative replication’ in the context of DNA.
Show how the Meselson and Stahl experiment provided evidence if support of
this mechanism of replication.
What
is mutation? What are the various types of mutations and explain the
molecular mechanisms. Explain frame shift mutation.
Show
how looping of DNA permits 5' ® 3' synthesis of the lagging strand.
What
are the various enzymes and proteins that involved in the process of DNA
replication in prokaryotes?
What
are topoisomerases? What are
the biological implications of topoisomerases?
Define
the terms ‘relaxed’, ‘positively supercoiled’ and ‘negatively
supercoiled’ and show how these are relevant to DNA replication.
Discuss
the role of negative supercoiling in DNA function, including transcription.
Explain
the polarity problem in DNA replication and how this is overcome.
Explain
the mechanism of methyl-directed mismatch repair.
Give
a comparative account of various types of DNA polymerase in prokaryotes?
Explain the role of each enzyme DNA replication and repair.
List
differences between eukaryote and prokaryote DNA replication.
Explain
various DNA repair mechanisms, which operate in E. coli with
examples.
What
are Okazaki fragments. Explain how it could solve the problem of polarity
during DNA replication.
Explain
the Klenove fragment. What is its practical application in molecular biology
experiments? Explain.
Explain
the terms ‘split genes’, ‘pseudo genes’ ‘overlapping genes’ and
‘cryptic genes ‘.
Differentiate
between overlapping gene and polycistronic gene. What is the advantage of
polycistronic genes?
Define
the terms ‘relaxed’, ‘positively supercoiled’ and ‘negatively
supercoiled’ and show how these are relevant to DNA replication.
What
is a replication fork? Explain about the enzyme complex present at the
replication fork in E.coli.
Explain
the mechanism of termination of DNA replication in bacteria.
What
is Xeroderma pigmentosum? How it caused.
Explain
the molecular mechanism of SOS response.
Explain
the mechanism of methyl-directed mismatch repair.
Describe
the events occurring to remove RNA, proofread and ligate DNA.
Histone
genes have the following features: a) no introns; b) the genes are arranged
in tandem arrays with one copy of each gene per group; c) the mRNAs have no
poly A tail. What explanation can be offered for these properties?
Give
a comparative account on the eukaryotic DNA polymerases and bacterial
polymerases, including its structural organization and function.
Explain
various mechanisms of gene regulation in eukaryotes.
Compare the structure and organization of eukaryotic genes with that of bacteria.
What are transcription factors (TF)? Explain how they are involved in the regulation of gene expression with respect to tissue, cells and age with suitable examples.