Sunday, July 28, 2013

Science Sunday: DNA Replication (Part 1)






DNA molecule
Posted by Rebekah




“I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.” Psalms 139:14 (KJV)
                           
                                                        and

“For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse.” Romans 1:20 (NASB)

Evolutionists would love to have people think that DNA (deoxyribonucleic acid) could have easily evolved.  “Besides”, they might desire to say, “DNA consists of phosphate backbones and nucleotide base pairs that, due to their structure, always combine in a certain fashion (adenine with thymine and guanine with cytosine)”; hence, asserting that DNA is really quite simple.

However, the hypothetical argument above is far from being truth: by developing a further understanding of DNA, one is lead to conclude that DNA is in fact tremendously complex.

This complexity is undeniably revealed when studying DNA replication, DNA expression, and “junk” DNA.

In this Science Sunday series, I will attempt to explain DNA replication both briefly and simply.  Lord willing, I will attempt to finish this series within three or four posts (but we’ll see what happens). Also, I may complete further series based on DNA expression and “junk” DNA.

Template Strands

After much experimentation, scientists have concluded that DNA, when replicating, follows a semiconservative model.

Here’s what this means:

DNA molecules have two complementary DNA strands: A (adenine) always hydrogen bonds to T (thymine) and G (guanine) always hydrogen bonds to C (cytosine). 




The two parental DNA strands separate; hence, becoming a template for the new strands that will form.





Complementary nucleotides now align to form a new strand (light green) that unites with the parental strand (dark green). The new DNA molecules are now formed.


A Brief Look at DNA Replication

Before we begin a more detailed examination of DNA replication, let’s have a brief view of what’s actually happening.

Look at the double stranded DNA molecule below (please note that the actual structure of DNA is double-helical). The origins of replication are specific sequences of nucleotides that “tell” certain proteins to begin replication—replication begins at the origins of replication.




When replication begins, replication “bubbles” form; consequently, forming replication forks. DNA replication proceeds in both directions from the origin. (Please note that the parental DNA strand is represented in dark green and the daughter DNA strand in light green).



The replication bubbles eventually fuse together; thus, resulting in two daughter DNA molecules.






Please note that the “brief look” I have just presented is that of a eukaryotic cell: prokaryotic DNA replication is a little different.

To be continued…
 

                                                            References 

Reece, Jane B., et al. Campbell Biology. 9th Global Edition. “Many Proteins Work Together in DNA Replication and Repair.” Boston: Pearson, 2011. 357-365. Print.



WARNING: Due to several reasons, I do NOT recommend Campbell Biology for your homeschool. However, due largely impart to its prevalent use in colleges and universities (and even Wikipedia), I chose to use it as a reference.