Introduction to DNABy Devin Murray

DNA is the code stored in individual genes. Recall that genes are specific sections of chromosomes.

Function: DNA’s code determines how all organisms look and act.

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What is the function of DNA?

Chromosomes are located in the nucleus and are stored just outside of the nucleolus.

So where are chromosomes again?

When you unravel tightly coiled DNA from the chromosome its overall shape of DNA is a double helix.

DNA structure

The most basic subunit of DNA’s double helix is called a nucleotide.

A DNA nucleotide has 3 parts: base, sugar, phosphate

DNA structure

Bases of the DNA nucleotide:◦ There are 4 nitrogenous bases: Adenine,

Thymine, Cytosine, and Guanine

◦ Nitrogenous means composed of nitrogen

◦ Bases are typically abbreviated by their first initial capitalized (i.e. A = Adenine, G = guanine, etc.)

DNA structure

Bases of the DNA nucleotide:◦ Bases pair together using these rules:

A pairs with T (or you could say T pairs with A) C pairs with G (or you could say G pairs with C)

DNA structure

Sugar in the DNA nucleotide:◦ The type of sugar in DNA is deoxyribose.◦ Deoxyribose is a 5 carbon sugar◦ This is the “D” in DNA.

Phosphate in the DNA nucleotide:◦ Compound with the chemical formula PO4

DNA structure

Sugar and Phosphate are in DNA typically referred to as the “The Sugar-Phosphate Backbone” because the pattern is like a chain repeating throughout the molecule.

From Nucleotides to DNA

The sugar of one nucleotide is linked to a phosphate of the next nucleotide by a covalent bond.

Nitrogenous bases are held together by hydrogen bonds.

From Nucleotides to DNA

Complementary base pairing(i.e. G-C and A-T) makes a long zipper like molecule of DNA.

The sequence of nucleotides bases forms the unique genetic code for an organism.

DNA’s code

1. In the cell, where are chromosomes are located?

2. What are the three parts of a DNA nucleotide?

3. What forms the unique genetic code for all organisms?

4. According to complementary base pairing rules, A pairs with __ and C pairs with __.

5. What type of bond secures the sugar-phosphate backbone of a DNA molecule?

Pop Quiz – 10 Questions

6. Describe the shape of a DNA molecule.7. What does the “D” in DNA stand for.8. What are the names of the bases

represented: A, G, C, T9. What are specific sections of chromosomes

called?10. Explain the meaning of nitrogenous.

Pop Quiz – 10 Questions

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United States Department of Health and Human Services. (2006, October). How genes work. Retrieved from http://publications.nigms.nih.gov/thenewgenetics/thenewgenetics.pdf

[Untitled drawing showing a chromosome is made of genes and genes are made of dna]. Retrieved March 9, 2010 from http://www.eurogentest.org/content/images/unit6/patientLeaflets/english/genesChromosomesDna.jpg

Works Cited