TRANSLATION
- Describe the process of translation: initiation, elongation and termination
In the process of translation, the ribosomes synthesizes (makes) proteins. It also translates the code that was delivered by the mRNA to a polypeptide.
Initiation : This is the process of when the ribosome, that is located in the cytoplasm, moves along a single strand and holds the mRNA (messenger) and reads the start codon. The 2 small ribosomal subunit binds also binds to mRNA. The messenger RNA consists of messages (3 letters) made out of RNA based off of the DNA.
As shown, the ribosomes moves along the strands and reads the strand from left to the right. The tRNA attaches to the “P” site and the “A” sire is empty until another tRNA comes in and attaches to the A site.
Elongation : This is the process of when the ribosome holds the mRNA and allows the complimentary tRNA (transfer) to transfer the amino acid that is holding to binding sites. The mRNA has 3 letter messages named codons and the tRNA has the complimentary (opposite) amino acid called anticodon. For example, if there is a codon that was AUG then the tRNA that has the anticodon of UAC will bind to the base. There are overall 64 possible codons that are made and is specific to one of the 20 amino acids. These tRNA is looking for complimentary bases and when they find their complimentary bases on the mRNA they transfer their amino acid that is held by peptide bonds and leaves the ribosome. There are basically 2 “spots” for the tRNA, one is the “P” site and one is the “A” site. Once the tRNA in the “P” site have transferred its amino acid to the tRNA in the “A” spot, it leaves. The last tRNA then moves to the spot in the “P” site and then another tRNA will occupy the previous spot and then the process repeats.
As shown in the picture, a tRNA that has the anticodon for the codons have attached to the strand and the “A” site is no longer empty.
This is what it should look like if the process repeats over and over again until the stop codon is read.
Termination: Usually at the end of an mRNA there is a stop codon. Stop codons do not hold amino acids, it usually means that the strand is finished. When the ribosome reaches it, it reads the codon and knows that the protein building is done. The codon does not have a matching tRNA as well so it cannot bond with any tRNA. The ribosome recognizes this and it dissociates into its 2 subunits.
2. Accuracy of the activity with translation? In what ways is it inaccurate?
The activity was accurate because it clearly showed how the tRNA in the “P” strand left and it transferred the amino acid to the other tRNA in the “A” strand. The ribosome was accurate as well the “P” and “A” site were on the ribosome and it is very easy to determine which site is which. Also, the little slit on the ribosome which allows it to move throughout the strand was very clever. As soon as I was done with the codons, I can just move the ribosome and the strand will just go through the slit and new codons will appear. It is inaccurate because it does not show or instruct us what happens after the ribosome reads the stop codon. The ribosome dissociates and lets go of the mRNA strand and it’s difficult to show this process in this activity.
TRANSCRIPTION
1) How is mRNA different from DNA?
The mRNA differs from the DNA because the DNA is its own strand while the mRNA is based off of the DNA strand with the exception of one of the bases, Uracil. The mRNA’s function is to deliver the copied strand from the DNA to the cytoplasm in which the ribosome is located. Once, held by the ribosome it shall read the strand and the tRNA will deliver the appropriate anticodon with an amino acid to the proper 3 letter word codon from the mRNA. On the other hand the DNA is made out of a phosphate sugar, deoxyribose and nitrogen bases. The DNA consists of genetic information and instruction for the development of living things or humans. mRNA is also single strand and short so it can leave the nucleus through a nucleus pore
2) Describe the process of transcription?
The process of transcription starts off with the unzipping a specific section of a DNA. After that, the strand is exposed and along the strand, complimentary RNA bases bond. After this, adjacent nucleotides form covalent bonds with the strand and starts to build the RNA backbone. This occurs with the help of the RNA polymerase. Lastly, the RNA is released and then the DNA reforms to a double helix. Also, there are 3 phases of transcription:
1: Unwinding and unzipping of DNA – a strand DNA unwinds and exposes itself
2: Complimentary base pairing – adjacent nucleotide bonds to “partner” nucleotide base
3: Separation from DNA. – RNA leaves the DNA
3) How did today’s activity do a good job of processing of RNA transcription? How inaccurate?
Today’s activity showed a good job of showing how the mRNA is being built. The DNA polymerase (purple) starts building the complimentary mRNA (red) as shown in the picture while the nucleotide base (A,C,U,G) are colour coded as blue, red, yellow, and purple. It was easy to determine which one is which in order to build the strand. The inaccuracy of this activity was hard to tell, all I can think of is the last phase of transcription, the leaving of RNA in the DNA. It was difficult for our group to come up with a way to show how the RNA leaves the DNA, we didn’t have enough or appropriate materials to display this process.