Answer
During gene expression an anti-codon of a tRNA pairs with mRNA bases.
A codon is a sequence of three nucleic acid bases( adenine, guanine,cytosine and thymine) that specify an amino acid. In RNA uracil is substituted for thymine.
A nucleotide is the basic unit of structure of a nucleic acid comprising a five carbon sugar ( ribose or deoxyribose), plus a purine or pyrimidine base, plus a phosphate group.
Work Step by Step
Gene expression comprises the processes by which the information encoded in the genes on our DNA is transformed into functional molecules --mainly proteins , but also m-RNA, tRNA, and small RNAs (smRNA).
All the cells of our bodies receive copies of all our genes, but cells vary in which genes they actively express. Thus nervous tissue and muscles vary in which set of genes are turned on in the nucleus and what proteins are active in the cytoplasm.
Genes exist in the nucleus as DNA sequences. In the nucleus a single strand of DNA is used as template
for the transcription by mRNA. The bases of the mRNA formed are complementary to the DNA bases. Three bases represent a codon. There are codons that specify amino acids (exons) and codons that do not (introns). When the mRNA strand is formed the introns are removed and the exons are spliced/joined together. This is mRNA processing. After the mRNA is processed transcription is over and the mRNA leaves the nucleus through nuclear pores.
In the cytoplasm the mRNA makes contact with a sequence of ribosomes( rRNA+protein) .
Transfer RNA (tRNA) bound to amino acids in the cytoplasm make contact with mRNA. Anti-codons ( base sequences complimentary to those of mRNA) pair with the codons of mRNA in an act of translation. The t-RNA translation of the mRNA takes place sequentially,resulting in the formation of a polypeptide chain. The polypeptide chain is later folded to form the protein expression of the gene (DANA sequence).
This is a very complex process and it is regulated through several stages: pretranscriptional--nucleus made available in the nucleus: transcriptional--determination of the degree to which the gene is to be transcribes; posttranscriptional-- involves m-RNA processing in the nucleus; translational-- determines the time of beginning and rate of translation and inactivation and degradation of mRNA, and postranslational control that occurs after protein synthesis.
Note to Editor:
The following answer is the correct answer that I want to submit for Assess 22.3:8. Please reject the
the former answer in that spot.
22.3:8
Ans,. The restriction enzymes found in bacterial cells are used to degrade viral DNA that enters the cells.
In bacterial cells there are hundreds of naturally occurring restriction enzymes. They cut up viral DNA that enter the bacterial cells; they thus restrict the growth of viruses and prevent viral takeover of bacterial cells--hence the name restriction enzymes.
In research enzymes are used as a kind of "molecular scissors" for cutting any piece of DNA at a specific site.
