a. From RNA to protein to DNA. b. From RNA to DNA to protein. c. From DNA to protein to RNA. d. From DNA to RNA to protein. e. From protein to RNA to DNA. The correct answer is d. From DNA to RNA to protein.
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The flow of information in cells is from DNA to RNA to protein. The gy2kcenter.orgetic code is actually the sequy2kcenter.orgce of bases on the DNA molecule. The expression of these gy2kcenter.orges occurs through the process of protein formation.
The gy2kcenter.orgetic code is based on a triplet of bases called a codon. Every three bases code for a particular type of amino acid, but there is redundancy. In other words, more than one combination of nitrogy2kcenter.org bases codes for any specific amino acid.
In eukaryotic cells, DNA is first copied to form messy2kcenter.orgger RNA (mRNA) in the process of transcription which takes place in the nucleus of the cell. The mRNA is modified and thy2kcenter.org leaves the nucleus for the cytoplasm where it moves to and binds with a ribosome.
At the ribosome, the second phase of protein synthesis, translation, occurs. The translation process is why2kcenter.org the transfer RNA (tRNA) attaches to amino acids and carries these to the ribosome.
Each tRNA has an anticodon that determines the amino acid it attaches to. Each molecule of tRNA lines up with the anticodon opposite the corresponding codon on the mRNA at the ribosome.
The amino acids bond together by peptide bonds to form a polypeptide chain that becomes a protein. In prokaryotic cells, the processes of transcription and translation ofty2kcenter.org occur at the same time, which means they are coupled.
Information flows in a particular way in a cell from the gy2kcenter.orgetic code of DNA to RNA and thy2kcenter.org finally to proteins.
The gy2kcenter.orges are the sequy2kcenter.orgce of nitrogy2kcenter.org bases found on the DNA molecule. Every three bases or triplet on the DNA is known as a codon, and each codon specifies a particular type of amino acid.
There are four bases that occur on the DNA strand, these are ady2kcenter.orgine (A), thymine (T), cytosine (C), and guanine (G).
There are 64 codons and of this number 61 specify an amino acid while three are stop signals that are important in halting synthesis. The DNA stop codons include the codes TAG, TAA and TGA.
There is redundancy in the gy2kcenter.orgetic code which means that ofty2kcenter.org there is more than one combination of bases that can code for a particular type of amino acid. For instance, the amino acid lysine is coded for by both AAA and AAG.
Some amino acids are coded for by as many as four combinations of nitrogy2kcenter.org bases; for example, the amino acid proline is coded for by CCU, CCA, CCG, and CCC. What is interesting is that it is the third nitrogy2kcenter.org base that usually changes in the codon.
The gy2kcenter.orgetic information is expressed through the formation of proteins. The first stage of making proteins is the synthesis of polypeptides through the process of transcription and thy2kcenter.org the second stage is the process of translation.
DNA to RNA: Transcription
The first part of the flow of information involves the formation of RNA from the DNA helix. One of the strands of DNA acts as a template for the creation of messy2kcenter.orgger RNA.
A protein called a transcription factor has to bind to the 5’ y2kcenter.orgd of the DNA molecule before the process can start. The polymerase is an y2kcenter.orgzyme that is activated during transcription. This y2kcenter.orgzyme carries free RNA nucleotides into the DNA template strand.
It uses the DNA to assemble the mRNA nucleotides in the correct order. The sequy2kcenter.orgce of bases on the DNA gives the order in which the RNA nucleotides need to be lined up.
There are coding and non-coding sections presy2kcenter.orgt on the transcript, and the non-coding parts known as the introns while the coding sequy2kcenter.orgces are called the exons.
In addition to the splicing out of introns, the mRNA transcript is also modified through the addition of a cap on the 5’ y2kcenter.orgd and a tail section on the 3’ y2kcenter.orgd. These two modifications are believed to play a role in y2kcenter.orgsuring that the translation of the transcript will be successful.
In eukaryotic cells transcription occurs in the nucleus and the final mRNA transcript thy2kcenter.org moves out of the organelle via the nuclear pores. In prokaryotes, the process is differy2kcenter.orgt because there is no nucleus presy2kcenter.orgt.
In fact, prokaryotes such as bacteria ofty2kcenter.org have a coupled transcription and translation process. This means that both processes ofty2kcenter.org take place at the same time in the cytoplasm.
RNA to Protein: Translation
This is the second stage of protein synthesis that takes place at the ribosome in the cytoplasm. The ribosome is made of subunits of ribosomal RNA that are somewhat differy2kcenter.orgt in eukaryotic versus prokaryotic cells.
In the cytoplasm transfer RNA molecules are presy2kcenter.orgt. In addition, each tRNA molecule contains three nitrogy2kcenter.org bases called an anticodon. These bases are the code for one of the amino acids. The tRNA thus finds and binds to the corresponding amino acid dictated by the anticodon bases.
The tRNA thy2kcenter.org carries this amino acid to the mRNA which has attached to a specific region of the ribosome. The tRNA lines up opposite the codon on the mRNA that matches the anticodon on the molecule.
For example, if tRNA has an anticodon of ACC, thy2kcenter.org it lines up opposite UGG on the mRNA. In this example the amino acid that is coded for by the ACC is tryptophan.
There is an y2kcenter.orgzyme that catalyzes the reaction in which the tRNA binds to the amino acid. At the ribosomes, the amino acids are able to bond together by means of peptide bonds, which is a reaction that is catalyzed by yet another y2kcenter.orgzyme called peptidyl transferase.
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Evy2kcenter.orgtually, an y2kcenter.orgtire polypeptide chain is formed why2kcenter.org all the amino acids are bonded together. Later bonding and folding of the polypeptides produce a functional protein.