Protein synthesis is the process in which cells make proteins. It occurs in two stages: transcription and translation. Transcription is the transfer of genetic instructions in DNA to mRNA in the nucleus. Translation is the process by which a ribosome reads mRNA’s message in order to string amino acids together and make the required protein. It includes three steps: initiation, elongation, and termination.

1. How is mRNA different from DNA?
   1. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. The only difference between ribose and deoxyribose is that ribose has one more -OH group than deoxyribose, which has -H attached to the second (2′) carbon in the ring.
   2. DNA is a double-stranded molecule, while RNA is a single-stranded molecule.
   3. DNA is stable under alkaline conditions, while RNA is not stable.
   4. DNA and RNA perform different functions in humans. DNA is responsible for storing and transferring genetic information, while RNA directly codes for amino acids and acts as a messenger between DNA and ribosomes to make proteins.
   5. DNA and RNA base pairing is slightly different since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Uracil differs from thymine in that it lacks a methyl group on its ring.
   6. DNA is significantly larger than RNA: DNA is about 85 million nucleotide pairs long while RNA is only about a 1000 nucleotide pairs
2. Describe the process of transcription-  a process which occurs because of the RNA polymerase, and results in one mRNA strand that carries instructions to build one protein (DNA molecule is unaffected by process in the long run)
   1. 1. Unwinding & unzipping of DNA: the DNA molecule untwists to look like a flat ladder, and the DNA helicase starts to break the H-bonds between complimentary nucleotide base pairs
      2. Complimentary base pairing with DNA: one strand of the two DNA strands will be used as a template to produce an mRNA strand (this strand contains the protein building instructions that will lead to the production of the correct protein (the other strand will not lead to a functional protein)). RNA polymerase is responsible for H-bonding RNA nucleotides to the template DNA strand and joining the adjacent nucleotides into a continuous backbone. 
      3. Separation from DNA: once the entire gene has been transcribed, the mRNA will separate from the DNA strand: which will continue on to reform into a double helix (ultimately unaltered by this process) and the mRNA is modified before moving out of nucleus and to deliver DNA’s message.
3. How did today’s activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?
   1. This activity was able to let us see the overall process of RNA transcription: clearly demonstrating the difference in nucleotide acids, and uracil instead of thymine, as well as showing the single backbone of RNA. It also showed some of the process of the RNA polymerase and it’s role in RNA replication. However, it was not able to capture all of the finer details of this process. As we were using pipe cleaners, we missed some of the key details that allows for RNA replication to happen as it does: a large factor being the size of RNA and DNA. The DNA should have been significantly larger than the RNA strand, as the RNA should only have coded for one protein- ours were the same size though. We also could not see all the details of the RNA polymerase as we demonstrated it building and adding nucleotides in one step, instead of how it actually attaches single nucleotides and bonds them beside each other for the backbone. Overall, the activity worked well for a basic and beginning understanding of the topic, however further learning and elaboration was clearly required to fully grasp the subject.
4. Describe the process of translation: initiation, elongation, termination:

• • Initiation: mRNA is held by a ribosome with an a-site and a p-site: once the p-site reads a start codon (AUG), the matching tRNA will bring in a corresponding amino acid to the start codon…

 

 

• • Elongation: the initiative process will continue and the amino acid chain will continue to grow. The a-site will read the next mRNA codon and bring in the corresponding matching tRNA. The amino acid change from the tRNA in the p-site will be transferred to the tRNA in the a-site

1. • Termination: once the next mRNA codon is a stop codon, as there are no tRNA for a stop codon, the amino acid chain will simple “stop”- the ribosome will let go of the mRNA and the tRNA will let go of the polypeptide.
2. How did today’s model do a good job of modelling the process of translation? In what ways was our model inaccurate?
   1. The process was able to correctly show how the translation process is dependant on the mRNA codes (start and stop codon, as well as everything in between). It also showed how the ribosome can accommodate two tRNA’s at once, as well as how the amino acids become attached and grow as a chain. However, it didn’t really show how the ribosome itself was made up of two subunits (our process demonstrated ribosome as one whole unit). The process also did not describe how translation will happen at multiple places at a time along a mRNA strand, as ours demonstrated it happening only in one location. Overall, the activity worked well for a basic and beginning understanding of the topic, however further learning and elaboration was clearly required to fully grasp the subject.