Genetic code consists of
Genetic code is the relationship of amino acid sequence in a polypeptide chain and base sequence of mRNA. It includes adenine, guanine, cytosine and thymine.
DNA replication is
In semi conservative replication of DNA in each replica one half is the old strand and the other half is a new strand synthesized over it.
In the genetic dictionary, there are 64 codons as
Genetic code is triplet coding for one amino acid in a polypeptide chain. There are four different types of nucleotides - A,T,G, and C. Since a code is a triplet thus 64 (4×4×4) distinct triplet of bases determine the 20 amino acids. But out of 64 only 61 code for 20 amino acids. Three codons that do not code for any amino acids are terminator non sense codons (UAG, UGA and UAA). Still in 61 triplet codons there is an excess 41 codons and therefore more than one codon codes for same amino acid.
A nucleotide is formed of
Nucleotide is a unit of DNA , which is formed of nitrogenous bases (urines & Pyrimidines), sugar (Pentose) & phosphate.
The process of transfer of genetic information from DNA to RNA/formation of RNA from DNA is
Central dogma of protein synthesis explains a unidirectional or one way flow of information from DNA to RNA (transcription) and from RNA to polypeptide (translation).
Escherichia coli fully labelled with 15N is allowed to grow in 14N medium. The two strands of DNA molecule of the first generation bacteria have
After one generation in 14N medium DNA of bacteria settled at a level intermediate between heavy and light bands due to semi conservative DNA replication.
Khorana first deciphered the triplet codons of
Hargonind Khurana first deciphered the triplet codon of cysteine and valine.
Experimental material in the study of DNA replication has been
Messelson and Stahl (1958) raised Escherichia coli on ammonium chloride having heavy isotope of nitrogen for several generations to study semiconservative replication of DNA.
Nucleotide arrangement in DNA can be seen by
In 1953 Wilkins obtained very fine X-ray crystallographic pictures of DNA from which Watson and Crick developed the double helix model of DNA.
A DNA with unequal nitrogen bases would most probably be
A single strand of DNA would not possess complementary base pairs. Hence nitrogenous bases are unequal in number.
The process of translation is
Protein synthesis occurs over ribosomes which are also referred to as protein factories.
During DNA replication, the strands separate by
Unwindase or helicase takes par t in separation of two DNA strands. In prokaryotes, helicase or unwindase is assisted by gyrase in this function.
Because most of the amino acids are represented by more than one codon, the genetic code is
All amino acids are specified by more than one codon (except Tryptophan and Methionine). Hence they are degenerate.
Who proved that DNA is basic genetic material?
Hershey and Chase (1952) worked on Escherichia coli and conclusively proved that DNA is the genetic material.
The transforming principle of Pneumococus as found out by Avery, MacLeod and McCarty was
The transforming chemical discovered by Griffith in his experiments with Pneumococcus, was confirmed as DNA by Avery, McLeod and McCarty.
Initiation codon of protein synthesis (in eucaryotes) is
[1993, 94, 99, 2000]
The initiation codon is the codon which initiates the protein synthesis. They are AUG for methionine and GUG for valine.
Protein helping in opening of DNA double helix in form of replication fork is
DNA gyrase participates in the unwinding of DNA helix during replication.
Which is not involved in protein synthesis ?
Protein synthesis stops when a nonsense codon (UAA, UGA or UAG) reaches the amino acyl or A site.
DNA template sequence of CTGATAGC is transcribed over mRNA as
[1994, 95, 2004]
During transcription, from the DNA template complementary mRNA is formed and thymine is replaced by uracil.
In Escherichia coli, lac operon is induced by
Lac operon is an inducible operon system which regulates genetic material. The genetic material remains switched off normally but becomes operational in the presence of inducer lactose.
Reverse transcriptase is
The phenomenon of making DNA over RNA genome through enzyme reverse transcriptase is called reverse transcription or teminism.
The number of base substitution possible in amino acid codons is
Codons are 6 in number. Each codon possess 3 bases, each of which can undergo transition and transversion. (1 × 32 = 549)
Out of A-T, G-C pairing, bases of DNA may exist in alternate valency state owing to arrangement called
The tautomer forms of nitrogen bases are immuno-tautomer instead of amino group (e.g. cytosine, adenine) or enol instead of the keto group (e.g. thymine, guanine).
Tautomers are organic compounds that are interconvertible by a chemical reaction called tautomerization. The concept of tautomers that are interconvertible by tautomerizations is called tautomerism. Tautomerism is a special case of structural isomerism and can play an important role in noncanonical base pairing in DNA and especially RNA molecules.
The wild type E. coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as sugar. Which of the following changes takes place?
If Escherichia coli bacteria grow in normal glucose medium and when transferred to a medium containing lactose, then the lac operon is induced.
In split genes, the coding sequences are called
The region of a gene, which becomes part of m-RNA and code for different regions of the proteins are called exons.