DNA: Structure and Function

DNA Structure Deoxyribonucleic acid. A macromolecule composed of two strands of monomers called nucleotides. These strands are joined in the middle by hydrogen bonds. The strands twist around one another forming a double helix.

Nucleotide Structure 5-C sugar – deoxyribose Phosphate group Nitrogen containing base -4 of two types –Adenine –Guanine –Cytosine –Thymine

Types of Nitrogen Bases Purines – have two rings in their structure –Adenine –Guanine Pyrimidines – have one ring in their structure –Thymine –Cytosine

Nitrogen Base Pairing Bases pair in a specific pattern. A purine always bonds to a pyrimidine Adenine bonds to thymine. Guanine bonds to cytosine.

Nitrogen Base Pairing The bases are held together by weak hydrogen bonds. The sides of the DNA ladder are composed of alternating sugar and phosphate and are called “backbones”.

Discovery of DNA Structure This structure was discovered by the work of James Watson and Francis Crick. These two scientists viewed x- ray images of DNA crystals that were created by Rosalind Franklin and Maurice Wilkins.

Functions of DNA DNA is the molecule of heredity. - It provides instructions for cell functioning and is a blueprint for the production of proteins that do the work of the cell. DNA must be able to copy itself exactly. - This process is called replication. - Enzymes control the process.

Replication – Overview  DNA “unzips” down its H-bonds  One strand then acts as a template for the production of a new strand  Each new DNA molecule has one old strand of nucleotides and one new strand.

Control Of Cell Activities DNA is copied into RNA. (transcription) RNA in turn controls the production of proteins. (translation) Proteins then do the work of the cell.

Frequently Asked Questions Why is DNA “twisted” Who named it DNA? Does the sound of your voice come from DNA? Do twins have the same DNA?

Why is DNA “twisted” This is caused by the bond angles of the covalent bonds between the carbons in ribose and the oxygen in the phosphate group. 12/ Bc.r.htmlhttp://madsci.org/posts/archives/ / Bc.r.html

Who named it DNA? DNA was named for the chemical components of the molecule – deoxyribonucleic acid- a result of cumulative work among scientists Francois Jacob on the naming of RNA named-messenger-RNA-Fran-ois- Jacob.html named-messenger-RNA-Fran-ois- Jacob.html