DNA and Protein Synthesis
- Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complimentary base pairing.
DNA contains two long antiparallel strands with four different types of nucleotides (adenine, thymine, guanine, cytosine).The four different nucleotides will join together in complementary base pairings (a->t, g->C) bonded together with 2 or 3 hydrogen bonds. The DNA backbones are made from phosphate and a pentose sugar, the two strands both are read in opposite directions.
- When does DNA replication occur?
Before a cell divides, there needs to be an extra set of DNA so that each cell can function correctly. So right before the cell divides the DNA strand will replicate in a semi conservative process. This means that each new strand contains 1 backbone from the original DNA strand.
- Name and describe the 3 steps involved in DNA replication. Why does the process occur differently on the “leading” and “lagging” strands?
The three main steps are the unwinding and unzipping of the old DNA strand, this will produce two complementary strands each with only one backbone. This process is done with the help of DNA helicase.
The next step is the complimentary base pairing this is done by two DNA polymerases, one leading strand which follows directly behind the DNA helicase in the same direction. The other is the lagging strand which is travailing in the opposite direction causing it to jump ahead to the DNA helicase before heading forwards until it reaches the point of its previous work, then the process repeats. Because of its habit of jumping around, there ends up being holes in the bonds between adjacent nucleotides.
These holes are fixed in the next step, which is done by the ligase, which follows behind the polymerase on the lagging strand creating bonds where the polymerase missed them.
Then 2 DNA strands identical to the original will remain both, containing half of the original DNA strand.
- Today’s modelling activity was intended to show the steps involved in DNA replication. What did you do to model the complimentary base pairing and joining of adjacent nucleotides steps? In what ways was this activity well suited to showing this process? In what ways was it inaccurate?
It was able to show the broad strokes of the process such as the leading and lagging strands and the ligase patching the holes. The Largest place of inaccuracy would be the scale. Normally each gene contains thousands of nucleotides where as our model only showed about a dozen. Our model was also extremely tight whereas normally the entire process would be much looser.
RNA.
- How is mRNA different than DNA?
Unlike DNA, which has a double helix structure, RNA has only one backbone. DNA’s backbone contains deoxyribose sugar, while mRNA contains ribose. DNA is more stable in alkaline conditions than RNA. RNA also has a slightly different base pairings, instead of thymine, RNA has uracil.
The two of them also have different functions. DNA’s main function is to store information whereas mRNA transports the information that is stored on the DNA. DNA is also self-replicating whereas RNA is synthesized from DNA as it’s melded.
- Describe the process of transcription.
To begin with, a gene on the one side of a DNA strand’s information will need to be caried into the cytoplasm.
The part of the DNA which contains the gene, which is to be copies split open,
then the mRNA copies the information from a specific side of the DNA strand. It does this with the help of RNA polymerase which forms complementary base parings with the DNA, with the help of loose nucleotides floating in the nucleus, to then form the RNA strand,
It then detaches as the DNA joins back together and rewinds.
The mRNA then carries the information to build the protein to the cytoplasm.
- How did today’s activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?
It can show very easily the difference in the sugars and the process of the sides of the DNA opening up. It doesn’t show case how the DNA only opens in specific sections of one gene as we can only see the split section. We also don’t get to see the polymerase doing its job, nor the reason behind transcription.
Protein Synthesis Model
RNA translation
- Describe the process of translation: initiation, elongation, and termination.
During the prosses of transnation the code Which the mRNA is transporting from the DNA will be transformed into polypeptides. The first step is initiation, where mRNAwill be bonded to a small ribosome called subunit. The subunit has two different locations a P site and an A site. Initially the P site will contain the start codon which will bond with a specific anticodon heId by a tRNA, and the A site contains the next in the sequence.
Each tRNA contains a specific amino acid depending on the codon. The tRNA located in the P site will passe its amino acid onto the amino acid located in site A, where it will form a peptide bond. The site P tRNA will then leave and the subunit will shift over causing the tRNA formally located in site A to now be located in site P. This process will repeat until it comes to a stopcock at which point the protein chain will be released
and the subunit will break apart as well.
- How did today’s activity do a good job of modelling the process of translation? In what ways was our model inaccurate?
The general broad stroke were good demonstrations such as the protein chan slowly forming as the tRNA leaves a good way to grasp the concepts. However, as with the previous models the scale is wildly inaccurate.