How is mRNA different than DNA?

The function of mRNA is to copy information carried by 1 gene on DNA. Since it is only single sided and short (unlike DNA, which has a double backbone), it is able to exit the nucleus through a nuclear pore. The instructions on the mRNA allow the ribosome to assemble the correct sequence of amino acids. Since DNA is too big and important to exit the nucleus, mRNA is crucial in building proteins.

Describe the process of transcription?

Transcription is a process which involves information being copied from a DNA gene, and is copied to a strand of mRNA. Only one strand of DNA has information that can be copied, and that strand is referred to as the “sense strand”. There are three steps in transcription: unzipping and unwinding, complimentary base pairing, and separation. In the first step, a section of the DNA strand unwinds, and then along the sense strand the RNA will bond their complimentary bases. The second step is the pairing of the bases between the sense strand and the RNA. The RNA builds a full copy of the strand by complimentary base pairing, however in RNA the base Thymine converts to Uracil. It separates itself from the DNA once a copy is made. This process is facilitated by DNA polymerase. The mRNA is read by the ribosomes in the cytoplasm to build a protein, in translation.

How did todays activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?

Today’s activity was helpful in demonstrating the complimentary base pairing, as we had different colours for every base. One inaccuracy could be the lengths of the DNA and RNA strands. Usually, the DNA strand is way longer, therefore the RNA only copies a certain section of it. In our models, the DNA and RNA strands were the same lengths.

Describe the process of translation: initiation, elongation, termination.

Initiation: In this step the ribosome identifies the start codon “AUG” to begin building the protein. Once the codon is identified, it is read in the P site.

Elongation: Once the start codon has been identified, every three bases after will be an amino acid to add to the protein. The ribosome will bring in the tRNA with the matching amino acid. It will situate itself in the “A” site. When both sites are full, the amino acid in the “P” site will move into the “A” site and attach itself to the amino acid on the “A” site. Then the tRNA and ribosome will shift so that the amino acids are now stacked in the “P” site. The process of continuously adding amino acids is only stopped once a stop codon is reached.

Termination: The elongation cycle ends once a “STOP” codon is read. Since it has no matching amino acid, the ribosome detaches from the mRNA.

How did today’s activity do a good job of modelling the process of translation? In what ways was our model inaccurate?

Using the paper model instead of pipe cleaner model had positives and negatives. It was way easier to move and understand the process of translation, due to lots of movement in the process. Since there are multiple steps that repeat themselves, using the paper made it quick and efficient. One inaccuracy is that the sugar-phosphate backbone was missing from the RNA strand, as it only showed the bases.