When does DNA replication occur?

DNA replication occurs before the mitosis stage because in mitosis the cells split therefore it cannot replicate. Specifically, DNA replication occurs in the nucleus of eukaryotic cells.

 

 

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

The 3 steps that are involved in DNA replication are Unwinding/Unzipping (Helicase), Complimentary base joining (Polymerase), and Joining of adjacent nucleotides (Ligase). Unwinding/Unzipping is where the DNA unwinds, and the 2 strands of DNA separate. As seen in the first picture, helicase is in the middle breaking the 2 strands apart. Complimentary base joining  is when new nucleotides move in to pair with bases of each template. Adenine-Thymine Guanine-Cytosine. Joining of adjacent nucleotides is when phosphate bonds forms between adjacent nucleotides of a new strand to complete the whole molecule. Joining of adjacent nucleotides also fills in gaps in Okazaki fragments. The process occur differently on the leading strand because as the helicase unwinds the DNA, the direction the left backbone strand is going (5′ to 3′) it is going upwards. 1′ always start with the Hydrogen bond (middle) moving clockwise, therefore the strand is touching the 5′ and 3′ on the left side. Whereas, the lagging strand is the opposite. The strand is touching the 3′ to 5′ moving downwards. Both strands moving the opposite direction.

 

 

 

 

 

Modelling complimentary base and joining adjacent nucleotides steps. In what ways was this activity well suited to showing this process? In what ways inaccurate?

This activity was well suited for displaying complimentary base joining because it is easy to identify which one is which. For example, there are several colours for each nucleotide bases such as A,G,C,T. Each one has their own colour and is very easy to know which one is which. It was very accurate to see if A was bonding with T or G bonding with C because of the colour code. Whereas, it’s inaccurate because sometimes I would make an error or a mistake with the colours it was difficult to remember which colour is which. Sometimes I would match A with G or C with T, I really needed to focus in order to do the whole strand. Also, while making the strand there were several times I ended up with an extra strand at the bottom which meant that I might’ve used the wrong strand to pair one of them, I had to look over every single strand to identify which was the mistake. For adjacent nucleotide joining, it was accurate because it showed how it glued strands together to make a whole molecule.

 

Explain the structure of a DNA

DNA is a large polymer made out of “nucleotides” monomers. Consists of 2 Carbon backbones formed by bonded sugar-phosphate portions of adjacent nucleotides. The 2 strands in the DNA are described as complimentary (strands gives the same message) and anti parallel (strands are red in opposite directions) Deoxyribonucleic acid is made out of sugars (deoxyribose), phosphates and nitrogen bases. Adenine pairs with Thymine and Guanine always pairs with Cytosine. Complimentary base pairing is when nucleotides bases bond with the other “partner” nucleotide base. As seen in the picture, we built the 2 backbones and are working pairing the appropriate “partner” nucleotide bases with each other.

How does this activity help model the structure of DNA. What changes can be made to improve the accuracy of  this model?  in detail

This activity displayed how accurate DNA backbones look like. It was easy and time consuming making the backbones but it showed every structure of a DNA, it’s easy to identify which one is which as well such as the backbones, the nucleotide bases, and sugar-phosphate. One way to improve the accuracy of the model is using another backbone material. The pipe cleaners are really good for this model but there are really sharp ends. I ended up poking myself like 20 times in this lab.