DNA Structure & Function

Cell Types Prokaryotic – cells lack a true nucleus Eukaryotic – cells have nucleus surrounded by a nuclear membrane

Nucleic Acids Organic Compound Consist of D N A & R N A Sugar Phosphate group Nitrogenous bases D N A & R N A

DNA Stands for DeoxyriboNucleic Acid Nucleic – located in nucleus Acid – acidic in nature

DNA is. . . Found in the nucleus of the cell The genetic material in each cell The chemical that processes and determines which proteins will be made by the cell

Nucleotides Subunit of nucleic acids 5 Carbon sugar called deoxyribose Phosphate Group 4 Nitrogen Bases

Nucleotide

Nitrogen Bases Adenine = A Thymine = T Cytosine = C Guanine = G

Nucleotides are connected by the attachment of the deoxyribose and the phosphate

Double Helix The sides of the helix/ladder are the alternating phosphate groups and deoxyribose sugars The rungs are paired nitrogen bases

Base Pairing Only certain bases can pair with each other Adenine with Thymine Cytosine with Guanine

Hydrogen Bonds The base pairs of the rungs (A - T & C – G) are held together by hydrogen bonds that are easily broken

Write the letters for the matching nucleotides on the strand of D N A: Remember that Adenine always pairs with Thymine. Cytosine always pairs with Guanine A T T A G C C G T A A G G A T C G T A A T C G G C A T T C C T A G C

DNA Structure & Function 2. D N A Function

Functions: D N A contains the genetic information to be passed on to the next generation D N A must replicate (for mitosis and meiosis) D N A is the template for R N A which is the template for proteins that determine a living organism’s traits

Gene A segment of D N A that codes for a specific trait

DNA Structure & Function 3. D N A Replication

DNA Replication Prior to cell division, the double stranded DNA molecule unwinds and is replicated Each parent strand remains intact and a new complimentary side is attached

Process: An “unwinding” enzyme breaks the hydrogen bonds between the nitrogen bases

Process: 2. DNA polymerase attaches free nucleotides to the exposed bases at the replication fork (according to base pair rules)

Process: 3. DNA ligase (another enzyme) seals the new nucleotides into a strand

Process: 4. Other enzymes go through and correct base pairing errors.

Process: 5. The resulting strands each have one new and one original piece of DNA New Strand Old Strand