DNA Structure 

1. Explain the structure of DNA – use the terms nucleotides, antiparallel strands, and complimentary base pairing.

DNA is a nucleic acid polymer.  The structure of it has a unique double helix ladder that forms a twist. The backbone of the DNA is composed of sugar, deoxyribose, and phosphate. Its rungs consist of two bases which are hydrogen-bonded to each other.  Those are adenine to thymine, and guanine to cytosine or simply A, T, C, and G.  The strands of DNA are always opposite on the other side from each other.  They complement each other that way creating one backbone which is opposite to its partnered backbone. 

     

  

2. How does this activity help model the structure of DNA? What changes could we make to improve the accuracy of this model? Be detailed and constructive.

The activity given to us was a very good demonstration to show how DNA looks. Using the pipe cleaners was very efficient way to bend and form into the shapes we needed.  By the end of each class fingertips hurt because of the wire but, I think it is was the most efficient and simple way to demonstrate the model. 

The beads indicated A, C, G and T and fit the pipe cleaners perfectly, it was a difficult clean up but when the DNA model was finished it looked great.

DNA Replication

1. When does DNA replication occur?                                                                      DNA replication occurs before cell division. 

2. Name and describe the 3 steps involved in DNA replication. Why does the process occur differently on the “leading” and “lagging” strands

• Unwinding& unzipping: the two sides of the DNA split and do not bond anymore. The enzyme is the DNA helicase that makes them unwind. 
• Complimentary base pairing: the back bones are used to make a new complimentary daughter strand. 
• DNA polymerase:  enzyme that creates the process
• Joining of adjacent nucleotides: the backbone has to have a continuous strand.

3. The model today wasn’t a great fit for the process we were exploring. What did you do to model the complimentary base pairing and joining of adjacent nucleotides steps of DNA replication. In what ways was this activity well suited to showing this process? In what ways was it inaccurate?

We had to attach white pipe cleaners that represented the nucleotides of half of the parent DNA to form a daughter DNA. The leading strand, had to be attached from the top to the bottom. When we did the lagging we did it from bottom to top. It was inaccurate because the DNA backbone isn’t one long strand of sugar phosphates like the blue pipe cleaner showed, it’s supposed to be the phosphates and sugars bonded together molecule by molecule as each nucleotide is paired. Even though some parts were not realistic, it was accurate because it gave us a good visual to show the same sequence DNA that was split to form same sequence daughter DNA.  Overall, the activity was interesting and really helped to remember the process of DNA replication. 

Protein synthesis: RNA Transcription 

1. How is mRNA different than DNA?

• mRNA carries DNA’s message while DNA doesn’t carry any RNA components
• mRNA has 1 backbone that is short  while DNA has 2 backbones that are long

2. Describe the process of transcription.

• Unwinding and Unzipping: DNA Helicase breaks the hydrogen bonds between the complimentary base pairs in the chain of nucleotides starting at the very top of the strand.
• Complimentary Base Pairing: One of the strands is used as a model to create an mRNA strand.  This is where the instructions for building proteins can be found. The other strand cannot be read because the message would not be the same as the mRNA strand concluding a protein cannot be produced from it. The RNA Polymerase joins RNA nucleotides to the DNA strand through hydrogen bonds in order to create a backbone of adjacent nucleotides. 
• Separating the mRNA from DNA: Once the transcription of the gene is has finished the mRNA separates itself from the DNA forming another double-helix shape.  The mRNA is then edited and leaves the nucleus to spread on the message from the DNA.

 

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

 This model did a good job of demonstrating the process of RNA transcription because we were able to show the mRNA latching onto the DNA and pairing up with the nucleotides.  It was difficult to show how the mRNA only attached onto some parts of the DNA, also we couldn’t show when RNA left the nucleus to pass the message to the DNA. 

Protein Synthesis: Translation 

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

• Initiation: translation starts. mRNA binds to the small ribosomes subunit, then the 2 ribosome subunits bind together.  They begin to read the first codon which is at the “P” site while the second is at the “A” site. 
• Elongation: ribosomes holds mRNA and allows complimentary tRNA to attach to binding site                                                                                                                                -mRNA has 3 letter code called “codon”

                   -tRNA has complimentary 3 letter code called “anticodon”

                   -each of the 64 possible codons is specific to one of the 20 amino acids

tRNA binds to the “P” site and another tRNA binds to an “A” site. Binding causes changes leading to amino acids letting go of tRNA and binds to neighbouring amino acids.
ribosome moves along mRNA to the 2^nd tRNA which is at “P” site and the new tRNA binds to the mRNA codon at the “A” site.

• Termination: The elongation cycle continues until mRNA reads a stop codon.  This is when the ribosome lets go of the mRNA, tRNA, and the polypeptide chain.

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

This model was accurate to show that the ribosome travel along as well as the process of elongation. Moving the pieces were a bit difficult, and taping them took a bit of time but it was worth seeing the change happen in front of our eyes, making it much easier to understand the process.