The Function and Structure of DNA

What is DNA? D = deoxyribo N = nucleic A = acid DNA is molecule that is a set of instructions for building and maintaining a living thing Many of the instructions are directions for carrying out the daily activities of the cell This information is stored and passed on from parent to offspring

DNA is like an instruction manual that can be read DNA is like an instruction manual that can be read. The instructions in DNA are mostly for making proteins which control everything How to make and maintain a human -2 ears -brown eyes -shy -time for cells are to divide -enzymes -speed of cellular respiration -one nose -position of arms -number of toes -transport proteins

Where is DNA found? DNA is found in every cell!!! Inside the nucleus of eukaryotes and cytoplasm of prokaryotes

Cell Differentiation ***Every cell in your body has the same copy of DNA instructions but… Cell Differentiation- All cells have the same DNA but certain instructions are turned on or off This makes Cells look and behave different

DNA Structure DNA is made up of units called Nucleotides. A nucleotide has three parts: 1. Phosphate Group 1 2 2. Deoxyribose Sugar 3 3. Nitrogenous Base

4 Possible bases A nucleotide always has a phosphate connected to a deoxyribose sugar which is connected to 1 of 4 bases Adenine (A) Guanine (G) Thymine (T) Cytosine (C)

Purines and Pyrimidines 2 types categories of bases: Purines: Pyrimidines:

How is DNA made? A DNA molecule is made by using covalent bonds to connect the sugar of one nucleotide to the phosphate of the next– forming a long single strand

5’ vs 3’ End

2 strands and Chargaff's rule *DNA is made up of 2 strands connected in the middle by the bases forming hydrogen bonds. *This looks like a ladder with a sugar/phosphate backbone and bases as steps *Chargaff’s base pairing rules (always, always, always): 2 hydrogen bonds Adenine Thymine A T 3 hydrogen bonds Cytosine Guanine C G ____________ ____________ __________________ __________________

The Double Helix The hydrogen bonds between the two strands twists them around each other into a double helix (twisted ladder). The two sugar-phosphate backbones are antiparallel to each other

Photo 51 Scientist Rosalind Franklin used X-ray diffraction to conclude DNA was a double helix with 2 negatively charged sugar-phosphate backbone on the outside with hydrophobic nitrogenous bases facing inward

Where are the “Instructions”? DNA has its “written” language or “secret code” to spell out instructions which uses only “4 letters” All genetic instructions are coded in the sequence of A,G,T and C Create your own sequence of at least 12 bases

ABCDEFGHIJKLMNOPQRSTUVWXYZ DOG GOD

Its universal!!! All living things on our planet have DNA for instructions The instructions are read the same way in all living things Each living thing/individual has a different set of instructions