DNA Replication:
Figure 1: The DNA molecule
1. Explain the DNA structure – Use the terms nucleotides, anti-parallel strands, and complementary base pairing:
Each DNA structure is composed of two anti-parallel strands that consist of nucleotides. The nucleotides are composed of a backbone which are made out of sugar and phosphate groups and nitrogenous bases named adenine, guanine, cytosine, and thymine. In addition, the nitrogenous bases are paired together, as adenine always pairs with thymine and cytosine with guanine which is referred to as complementary base pairing. The bases are ultimately held together by hydrogen bonds and make up the structure of DNA.
2. When does DNA replication occur?
DNA replication occurs just before a cell divides, so that the daughter cells will have the same type of genome as the parent cell and for it to perform the same type of function.
3. Name and describe the 3 steps involved in DNA replication. Why does this process occur differently on the “leading” and “lagging” strands?
The 3 different steps involved in DNA replication are unzipping, complementary base pairing, and adjacent nucleotide bonds. In the unzipping process, the DNA double helix unwinds itself and the two strands become separated. The hydrogen bonds between the complementary base pairings are also broken. The next step is complementary base pairing and this process involves nucleotides pairing up with the bases. The last process is called adjacent nucleotide bonds and this is where sugar-phosphate groups are formed between each adjacent nucleotide. This process occurs differently on the leading and lagging strands because the leading strand has nucleotides added to the 3′ end and the lagging strand has nucleotides added to the 5′ end.
Figure 2: DNA molecule
Figure 3: DNA replication
4. Today’s modelling activity was intended to show the steps involved in DNA replication. What did you do to model the complementary base pairing and joining of adjacent nucleotide steps? In what ways was this activity well suited to show this process? In what ways was it inaccurate?
What I did to model the complementary base pairing and the joining of adjacent nucleotide steps was using different type of polygons and hexagons that represented adenine, guanine, cytosine, and thymine and the sugar and phosphate groups. I joined them together using the whiteboard to make a strand of DNA. This activity was well suited to show this process because it allowed me to further understand DNA replication and the complicated process in a more visual, cut-down aspect. This activity was also un-accurate because the sugar and phosphate groups were hard to put in the right specific shape and I also didn’t make the strands anti-parallel, since it was difficult to do so.
Transcription:
- How is mRNA different than DNA?
mRNA is different from DNA since it consists of the sugar ribose instead of deoxyribose, it’s single-stranded instead of double stranded, and mRNA consists of uracil instead of thymine as its pyrimidines base.
2. Describe the process of transcription.
The process of transcription involves a gene DNA sequence which is copied, so that it becomes a RNA molecule. In order for transcription to occur the DNA molecule must unwind in that section where the specific gene is going to be utilized for transcription. Only one of the strands of the double stranded DNA is used as a template for the RNA product, and it’s almost identical to the template but instead of thymine the base uracil is used. The RNA polymerase is used in transcribing DNA into RNA by adding the complementary base pairs and it goes in the 5′ to 3′ direction. It attaches to the DNA molecule at the end and begins reading the strand of DNA until it reaches a stop codon.
3. How did today’s activity do a good job of modelling the process of RNA transcription? In what ways was our model inaccurate?
It showed a very simple, condensed process of modelling the process of RNA transcription and it was a visual that I can look back at for future purposes. This model was inaccurate because the mRNA strand template is much probably much longer than what I made here. In addition, this activity was tedious and it made me more stressed out about making sure I labelled everything correctly instead of actually being able to use it to learn something. It also goes much faster in real life and obviously much smaller scale.
Figure 4: Transcription
Translation:
1. Describe the process of translation: Initiation, elongation, and termination.
The process of transcription involves three steps which are called initiation, elongation, and termination.
Initiation: This is the beginning stage and in order for it to begin there has to be a ribosome, a mRNA, and an initiator tRNA (this is what carries the first amino acid). All three of these components come together to form the initiation complex, so that a protein can be successfully made. At the beginning, the tRNA that carries the MET codon has to attach itself to the ribosomal subunit and both of them afterward attach themselves to the end of the mRNA. Then, they both go in the 3′ direction along the mRNA and they come to a halt once they are able to reach a start codon (AUG).
Elongation: This stage is in the middle and this is where the polypeptide chain continues to grow and grow. The first tRNA that is carrying the MET begins in the P site of the ribosome and another new codon is in the A site of the ribosome. The A site acts as the “landing site” for the incoming tRNA that has an anti-codon that is to be matched with the codon that is exposed. When the tRNA has reached the A site, then a peptide bond begins to form between the amino acids. It takes the first tRNA and places it onto the amino acid of the second tRNA. New codons continue to become exposed in the A site, so that the process can be repeated many times.
Termination: This stage is reached once the ribosome encounters a stop codon that is on the mRNA in the A site. There are release factors that don’t allow peptide bonds to form and create a water molecule to be added on the last amino acid. Then, the chain becomes separated from the tRNA and a protein is formed and released.
2. How did today’s activity do a good job of modelling the process of translation? In what ways was our model inaccurate?
Today’s activity did a good job of modelling the process of translation because once again it was able to give a good visual representation of what happens during translation. It’s more applied and it allowed for me to get a better understanding of what happens during the stages. The model was inaccurate because of its size and there are way more codons used to form the polypeptides. The process would also be more accurate, efficient, and quicker in reality.
Figure 5: Initiation
Figure 6: Termination