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DNA basic structure


Here we go! The amazing cell and DNA size and scale app! website.

What is DNA? How is it related to heredity?

DNA, or deoxyribonucleic acid, is a very long chemical that stores information on how to build cells, and all the instructions necessary to build an entire living organism.

Let’s start building DNA, from the ground up. DNA starts with small pieces (bases), then builds into larger pieces (nucleotides), then much longer pieces (genes) and finally into huge assemblies called chromosomes.

Here are the four bases of DNA

{ http://faculty.ccbcmd.edu/~gkaiser/biotutorials/dna/fg4.html }


When in a gene, these always pair up with their compliment:

A with T,  and G with C

We call them complimentary pairs

{ http://weloveteaching.com/0bio105/lectures/organics/nucleotides.html }


These bases are held together with a sugar-phosphate backbone:

The base connects with a sugar, and a phosphate to make a nucleotide.


Many nucleotides come together to build a double-helix. But first,  what is a single helix?

{ http://solidwize.com/fun-with-sketched-bends/}


Here is a spiral staircase, in the Old State House, Boston, Massachusetts

{ http://www.joeyblsphotography.com/slideshow/historic-old-state-house-antique-spiral-staircase-in-boston/ }

The Spiral Staircase in the Old State House in Boston

{ http://www.britannica.com/EBchecked/media/95480/Old-State-House-Boston }

What is a double helix?

It is the shape made when you take a ladder, and twist it like this:

{ http://lanbob.com/lanbob/H-Biology/H-Biology-001.htm }


Let’s take nucleotides and assemble them into a double-helix, like this:

{ http://www.slideshare.net/coachpointer/dna-notes-7177774 }


There are other chemicals that have to do with genetics: Not just DNA, but also RNA.

We’ll get into RNA later.

Note that while DNA usually has a double helix shape,
RNA usually has a single helix shape, like this:

{ http://mappingignorance.org/2013/04/30/life-and-deeds-of-rna-i-william-wallace-and-the-fate-of-the-cell/ }


To think about:

* Describe DNA’s function in genetic inheritance.

* What is the purpose of doubling up (complimentary) the base pairs?

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