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Watch this video to learn about ribosomes. The ribosome binds to the mRNA molecule to start translation of its code into a protein. What happens to the small and large ribosomal subunits at the end of translation?

Translation works because each unique anticodon carries a specific amino acid. The same anticodon carries the same amino acid in virtually all living organisms on earth. This is why gene splicing and genetic engineering work. The complete collection of amino-acid/nucleotide-sequence relationships is called the Genetic Code . However, the Genetic Code uses the complementary mRNA codon sequences rather than the tRNA anticodon sequences to denote the relationship with the amino acid. The Genetic Code is presented in various formats. The two most common are the table format (not shown) and the wheel format shown below ( [link] ).

The genetic code

This version of the genetic code is displayed as four concentric circles. The inner most circle contains the first letter at the five prime end of the codon. The second ring contains the four possibilities for the second letter for each of the inner circle letters. The third ring contains the four possibilities for each of the letters in the second ring. The fourth ring contains the specific amino acid each triplet combination codes for each combination.
Genetic Code By Mouagip: Public domain, via Wikimedia Commons

The wheel is read from the center out (in the 5' to 3' direction). It is read by finding the first letter of the codon sequence in the inner most circle, then finding the second letter of the codon sequence from the four choices next to it in the second ring. The process is repeated in the third ring by choosing the third letter of the codon sequence from the four choices next to the second letter. The amino acid associated with the codon is found in the adjacent segment outside the circle.

Notice that four of the codon sequences have special significance. The sequence AUG is the start codon. This tells the ribosome where to start the translation. It also codes for the amino acid methionine. The other three special codon sequences are, UAA, UAG, and UGA. These are the stop codons. When the ribosome encounters these codons it stops the translation and releases the newly formed protein.

Looking at the amino acids around the outside of the wheel you also should notice that while each codon sequence is specific to a single amino acid, the reverse is not true. Most of the amino acids are associated with more than one codon. This redundancy in the Genetic Code can have a significant effect in some circumstances. Point mutations can occur in the DNA where one base is substituted for another. Even though the DNA has a mutation, the sequence now is different, if the resulting mRNA codon still codes for the same amino acid the resulting protein will not change. When this happens it is called a silent mutation .

Gene mutations

There are many ways the DNA can be altered by mutation. However, the changes to the original sequence are one of the three generic types:

  • Base Substitution: where one base is replaced by another
  • Insertion: where one or more bases are added to the sequence
  • Deletion: where one or more bases are removed from the sequence

The effects of the mutation will differ depending on the specifics of each case. The effect generally will fall into one of four categories:

  • Missense: where the mutation codes for a different amino acid at that location changing the resulting protein
  • Nonsense: where the mutation codes for one of the three stop codons stopping the translation early
  • Silent: where the DNA sequence changes but still codes for the same amino acid so the resulting protein is unchanged
[link] )

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Good
what does post-translational control refer to?
Teresa Reply
Bioremediation includes
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Source:  OpenStax, Ucd bis2a intro to biology v1.2. OpenStax CNX. Sep 22, 2015 Download for free at https://legacy.cnx.org/content/col11890/1.1
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