Transcription and translation

Transcription is the first step in gene expression that are copied into RNA enzymatic RNA polymerase specific segment of DNA. RNA and DNA is a nucleic acid base pairs using a nucleotide having additional languages ​​may be by the action of the right enzyme to convert back and forth to the RNA from the DNA. During transfer, further, DNA sequence results in antiparallel strand RNA, and is read by RNA polymerase. In contrast, thymine (T) would not occur in the complement of the DNA transcription, and in each case, DNA replication leads to complement RNA containing uracil (U). Further, in contrast to the replication of DNA, DNA is synthesized and does not include a transfer RNA primers to initiate synthesis of RNA.

Transcription and translation

Is a DNA sequence containing the genetic information, the gene is able to influence the phenotype of an organism. Sequence of bases along the gene within the DNA chain defines the RNA sequence is the protein sequence determination of one or more. Relationship between the nucleotide sequences of the amino acid sequence of the genes and proteins were determined by translation rules, known as the genetic code. Genetic code is composed of letters “keyword”, 3, called codons, which is formed by a sequence of three nucleotides.

In the transfer, codon of the gene is copied into RNA by RNA polymerase. Copy RNA is decoded by the ribosome reads the nucleotide sequence of the RNA of the RNA binding transfer RNA carrying the amino acid thereafter. Since there are four bases with a combination of three letters 64 possible codons (in combination). Encoding twenty standard amino acids thereof, most amino acids are possible codons plurality. Yes it is “nonsense” codon marks the end of the coding region or “stop” of three there, they have a TAG codon TAA, and TGA.

Transcription is the first step leading to gene expression. Is called a transfer unit, a stretch of DNA transfer has genes encoding the at least one RNA molecule. Thereafter, the process of translation, the result of the transfer messenger RNA is used to produce this protein (mRNA), transcribed genes, when encoding the protein. Alternatively, (for example, micro-RNA, etc. lincRNA) ribosomal RNA and or (rRNA gene) transfer RNA (the tRNA), transcribed genes encodes a ribozyme or non-protein components, the assembly process non-coding RNA genes get.

The transfer unit of DNA encoding the protein, and a sequence not only can not only convert the protein (coding sequence), controls the regulatory sequences direct Finally, to adjust the synthesis of this protein . Coding sequence is called (ie, upstream) 5 president untranslated region of before (5’UTR), and coding sequence, a series of the following (downstream) 3 prime untranslated region regulatory sequences, (3 ‘UTR it is called). Transfer some correction mechanism, is because it is less effective than the control in the copy of DNA transcription, the accuracy of the copy DNA replication is low they.

As the replication of DNA, DNA is read from the 3’UTR → 5’UTR during transfer. On the other hand, RNA complementary is created by 5’UTR → direction 3’UTR. That is, the 5 ‘end was first created in base pairs. And is formed by anti-parallel strands of two DNA double helix, but is used to transfer only one of the two strands of DNA called the template strand. In comparison with only double-stranded DNA RNA, it is because it is single-stranded. Since sequences are the same (except substitution of uracil for thymine) RNA transcript fresh, DNA encoding the other chain is a (gap) direction. You can use the 3’UTR → 5’UTR circuit only need to Okazaki fragments seen in DNA replication is eliminated.

The virus of some, I have the ability to transcribe RNA (for example, due to HIV, AIDS), to DNA. You have the HIV RNA genome is replicated in DNA. DNA thus obtained may be fused to the genomic DNA of the host cell. Major enzyme involved in the synthesis of RNA from DNA are called reverse transcriptase.  In the case of HIV, reverse transcriptase is responsible for synthesis of a complementary strand of the DNA of the virus genome RNA and (cDNA). It is an enzyme ribonuclease H, in order to form a double helix structure of DNA (“on cDNA”), reverse transcriptase and RNA synthesize a complementary strand of DNA next. It was integrated into the genome of the host cell integrase enzyme that causes a host cell in order to repeat the cDNA of decomposing to produce viral proteins incorporated into new virus particles. In HIV, as a result, the host cells undergo apoptosis or programmed cell death of T cells. However, in other retroviruses, as the virus buds from the cell, the host cell, has been left as it is.

In eukaryotic cells, specific, and includes an enzyme having reverse transcriptase activity called telomerase. Telomerase is a reverse transcriptase which extends the ends of linear chromosomes. The synthesized “junk” DNA or DNA sequences that are repeated, telomerase RNA carry therefrom. This iterative sequence can be called a telomere DNA, is considered as a “cap” on chromosomes. Linear chromosomes since the duplicated each time, which is important, it is shortened. Not a repeat sequence is not essential for DNA sequence encoding a protein located at the ends of chromosomes, some of them, but ends of chromosomes, “hat” or “junk” DNA, the shortening is eliminated. Often, without losing the DNA sequence cancer cells encode proteins important in order to be able to replicate their genome indefinitely, Telomerase is activated in cancer cells. Activation of telomerase may be part of a process that allows cancer cells become immortal. By using the remaining 10% of the alternate route is known as the alternate telomere elongation and maintenance ALT telomere, telomerase in recycling factor cancers indicates that occur in 90% of the carcinogenic all tumors in vivo by telomere elongation Because it is.