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Nucleic Acid Function:
DNA Replication, Transcription & Translation
from Science Prof Online
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DNA must be copied before a cell can divide, and the genetic instructions in DNA are carried out as the cell builds proteins. These activities that nucleic acids are involved in are called:
- Replication: The duplication of genetic material.
- Transcription: Transcribing the genetic code of DNA into RNA molecules.
- Translation: RNA following DNA’s instructions for building proteins from amino acids.
Genetic Replication
Before a cell divides, it must make a copy of its DNA so that both parent and daughter cell have a complete copy of genetic information. This process of copying the double-stranded DNA molecule is called replication. This process takes place in the nucleus of eukaryotic cells and the nucleoid region in prokaryotes.
Each DNA strand holds the same genetic information, so both strands can serve as templates for the reproduction of the opposite strand. The template strand is preserved and the new strand is assembled from nucleotides (semiconservative replication). The resulting double-stranded DNA molecules are identical.
Genetic Transcription
This is the process by which a DNA sequence is copied to produce a complementary strand of RNA. In other words, it is the transfer of genetic information from DNA into RNA. The process is similar to replication, but in this case, RNA is being built, rather than DNA. Transcription is the beginning of the process that ultimately leads to the translation of the genetic code into a peptide or protein.
Three types of RNA are transcribed from DNA:
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
Messenger RNA is a copy of the genetic information that was transcribed from the DNA.
This copy is brought to the ribosome and “decoded” by tRNA and rRNA. Ribosomal RNA (rRNA) is part of the structure of ribosomes, the cellular protein factories where peptides are built. Transfer RNA (tRNA) brings to the ribosome the amino acids that mRNA coded for.
Article Summary: Nucleic acids, such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the vital genetic blueprints, messengers and builders of the cellular world.
DNA Replication, Transcription & Translation
Genetic Translation
Ribosomes (which contain rRNA) make proteins from the messages encoded in mRNA. Each three nucleotide group, called a codon, encodes one amino acid. This is the genetic code. In other words, the triplet code of genetic instructions for a polypeptide chain is ‘written’ in the DNA as a series of 3-nucleotide ‘words.’
These genetic instructions are brought to the ribosome by mRNA, decoded by rRNA, and tRNA brings the amino
acid monomers that were coded for in the base triplet of mRNA. Amino acids are monomers that, when linked together with peptide bonds, ultimately become a protein molecule, the end product of translation.
Sources
- Bauman, R. (2005) Microbiology.
- Park Talaro, K. (2008) Foundations in Microbiology.
This article originally appeared on Suite101 online magazine.
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