Summary of Transcription, Translation and Replication Notes
The three main activities that nucleic acids are involved in are:
1. Replication: The duplication of genetic material.
2. Transcription: Transcribing the genetic code of DNA into RNA
molecules.
3. Translation: RNA following DNA’s instructions for building
proteins from amino acids
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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.


Transcription occurs in the nucleus.
Transcription in the process by which RNA is assembled from a DNA
template.
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.
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.’ Protein Synthesis: An Overview
DNA
(Gene
Allele)
--
Transcription
-->
(in nucleus)
Translation
RNA -- (in cytoplasm) --> Protein
Translation
Translation occurs in the cytoplasm
Protein synthesis is accomplished through a
process called translation. After DNA is transcribed
into a messenger RNA (mRNA) molecule during
transcription, the mRNA must be translated to
produce a protein. In translation, mRNA along with
transfer RNA (tRNA) and ribosomes work together
to produce proteins.
Transfer RNA plays a huge role in protein synthesis
and translation. Its job is to translate the message
within the nucleotide sequence of mRNA to a
specific amino acid sequence. These sequences are
joined together to form a protein.
How to Separate DNA into Codons
• For example,
. Convert the
TGTCTTTTGGGA… becomes TGT/ CTT/ TTG/ GGA…
DNA codons into mRNA using the following rules: • T- A
A-U
C -G
C
• Therefore,
ACA/ GAA/ AAC/ CCU…
TGT/CTT/TTG/GGA becomes
G-