DNA is transferred to peptide

4 pages (1000 words)

How information stored in DNA is transferred to peptide?

The two processes mainly involved in the transfer are translation and transcription. DNA   when it codes for the synthesis of RNA is called transcription and when RNA codes for the synthesis of protein the process is termed as translation. During this process there is replication of the DNA prior to cell division carried out by the enzyme DNA polymerase. The process of transcription is carried out by RNA polymerase which always begins at the 5’ end and the RNA that is involved in the process is called mRNA.

The initiation of the process is done by the enzyme RNA polymerase when it binds to promoter and after the beginning of the process the sigma factor dissociates. After the process of initiation there is elongation of mRNA where the enzyme polymerase moves along the DNA template in 5’ to 3’ direction where the enzyme adds nucleotides to the growing chain. The process of translation is completed when the enzyme encounters translation terminator at the hairpin loop and dissociates into a template.

The process of translation requires tRNA and rRNA where the process of translation of transfer of amino acid to poly peptide chain is done by tRNA. The protein synthesis starts in the presence of rRNA. The site at which the ribosome binds to mRNA is called ribosome binding site. The translation starts at the AUG codon where more and more ribosome’s are added in the process and leads to elongation of the chain. A stop codon terminates the process or translation and a newly formed polypeptide is released.

  1. What is a mutation in molecular terms?b. if a. mutation deletes a base in the genomic DNA discuss how that will affect the reading frame and expression product production.

The changes in the base pair sequence of genetic material caused by errors in cell division or exposure to chemical mutagens, radiations, or viruses is called mutation. Changes in humans or animals such as natural selection remove unfavorable mutations and the favorable ones result in changes. Chemicals which effect the DNA replication cause Point mutations. There is an exchange of purine to purine or pyramidine to pyramidine. The reversal or a point mutation is done by another point mutation and the changes are classified as transversions and transitions. The other changes include Insertions where there is addition of one or more nucleotides. Deletions where there is removal of one or more nucleotides. Amplifications where there are formation of multiple copies of genes. Chromosomal translocations leading to exchange between genes of nonhomologus chromosomes. The main causes leading to mutations are Tautomerism, Depurination leading to loss of purine base, Deamination. Chemicals and ultraviolet radiations can cause changes in base pairing properties in the DNA structure. These changes are harmful and beneficial depending on the effect the cause and changes they make in the gene pool.

  1. Discuss, using the lac operon, how induction controls enzyme synthesis.

b. Discuss, using the tryp operon, how metabolite or end product repression controls enzyme induction.
c, How can we explain why E.coli grown in the presence of both glucose and lactose uses glucose preferentially e.g. catabolite repression

Lac operon is known as lactose operon is a group of linked genes controlling the synthesis of beta galactosidase, galactoside premise etc. When the inducer is added to the culture the synthesis of galactosidase starts and the process can be terminated by the removal of the inducer from the process.

Tryptophan operon consists of Tryptophan which acts as a co repressor which has its effects on expression of transcription. Operon consists of structural genes and the promoter where in the presence of co repressor repression or transcription of structural genes occur and in the absence of the latter transcription of structural genes occur.

Catabolite repression was earlier termed as glucose repression where during the culture glucose prevents the formation of cAMP which is used for the regulation of activity of CRP. Where CRP plays an important role in regulation of transcription of large number of operons.

  1. If you knew the amino acid sequence of a peptide could you use that information to find the gene in a pool of genomic DNA. If so, how might you do this.b. How does a cell recognize which strand is the sense strand? How does the RNA polymerase enzyme actually know where to start making a message. Flow about stopping?
    c. What is PCR? How do you do it?
    d. What is RNAi?

The sense strand begins from the 5’ end and goes to the 3’ end which is also called as the coding strand which contains same information as of the anti sense strand. The two strands run anti parallel to each other.

Polymerase Chain Reaction is a process of production of mass quantities of DNA for experimental purpose. A solution containing primers and a strand of DNA is heated for 100 degrees C at a point where DNA strands break and on cooling the primers bind to the DNA strands leading to the formation of two new DNA molecules single stranded and double stranded before and after the primer.

A double stranded RNA(dsRNA)  when suppresses the process of gene expression is called as RNA interference which is also know as post transcriptional gene silencing.

  1. Discuss three ways that bacteria can transfer DNA between cells,

b. What is the difference between lyric and lysogenic viral replication?

In bacteria gene transfer occurs in three ways:




Bacteria after lyses release structural DNA in to the environment which is take up by other bacteria by the process of recombination thus leading to the process of transformation.

Transfer of the DNA using a virus also known as a bacteriophage is called transduction. The virus infects the bacteria and carries the DNA to another cell and transfer the DNA by injecting into the bacterial cell resulting in cross over linkage producing a recombinant cell.

The process of conjugation requires plasmids which are male and female in structure. The transfer of plasmids from male to a female occurs through a cytoplasmic bridge which transfers plasmids from male to female resulting in the formation of two male cells.

Lytic cycle involves attachment of T4 to the receptors on the E.coli cell wall and penetration is done by tail core and the DNA is injected. Parts are synthesized using the host cell and phages mature after the parts are assembled. As the name suggests the new phages are formed after the lyses takes place.

Lysogenic cycle includes attachment of phage to E.coli and injection of DNA. In this cycle the circular phage DNA combines with E.coli DNA leading to the formation of prophage. It undergoes cell division leading to the formation daughter cells with prophage which undergoes lytic cycle.