Molecular basis of organ differentiation depends on the modulation in transcription by
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Solution
The process of formation of protein sequence from DNA strand is called transcription which requires RNA polymerase chain. RNA polymerase chains are of 3 -types in eukaryotes
(i) RNA polymerase-I
(ii) RNA polymerase-II
(iii) RNA polymerase-III
One gene-one enzyme relationship was established for the first time in
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Solution
It was given by Geneticists George W. Beadle and E. L.Tatum which states that each gene in an organism controls the production of a specific enzyme. It is these enzymes that catalyze the reactions that lead to the phenotype of the organism.
The length of DNA molecule greatly exceeds the dimensions of the nucleus in eukaryotic cells. How is this DNA accommodated?
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Solution
The nucleosome model explains the packaging of histone proteins and DNA in the chromatin material which forms the chromosome.
The okazaki fragments in DNA chain growth
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Solution
Okazaki fragments in DNA are linked up by the enzyme DNA ligase. Replication always occur in 5' - 3' direction. Okazaki fragments synthesized on 3' - 5' DNA template, join to form lagging strand which grows in 3' - 5'direction.
One gene -one enzyme hypothesis was postulated by
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Solution
Beadle & Tatum postulated the theory of ‘One-gene-one-enzyme’ in which they stated that in any living cell there are number of genes present on chromosomes in a linear fashion. One single gene controls the synthesis of one particular enzyme (or protein) in the cell which is responsible for its phenotypic character.
Which one of the following makes use of RNA as a template to synthesize DNA?
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Solution
Reverse transcriptase (RNA dependent DNA polymerase) is present in some retroviruses e.g. HIV virus.
During transcription holoenzyme RNA polymerase binds to a DNA sequence and the DNA assumes a saddle like structure at that point. What is that sequence called?
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Solution
About 28 base pairs from transcription start site are TATA boxes. After 40 bases from TATA boxes appears LAAT boxes. Both of these sequence serve as recognition site in eukaryotic promoters (Transcription in eukaryotic genes in a far more complicated process than in prokaryotes).
E.coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because:
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Solution
Operons are segments of genetic material which function as regulated unit or units that can be switched on and switched off. An operon consists of one to several structural genes. (Three in lac operon).
These are genes which produce mRNAs for forming polypeptides / proteins / enzymes. Z (produces enzyme β galactosidase for splitting lactose into glucose and galactose). Y (produces enzyme galactoside permease required in entry of lactose).A (produces enzyme thiogalactoside trans-acetylase).
The three structural genes of the operon produce a single polycistronic mRNA.
In transgenics, expression of transgene in target tissue is determined by
During replication of a bacterial chromosome DNA synthesis starts from a replication origin site.
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Solution
Replication begins at the Ori- origin of replication and proceeds on both sides from the Ori. Unidirectional replication is rare. RNA primers are involved in both prokaryotes and eukaryotes.