1. DNA How are cells structured to do the “right” thing?

2. Structure of DNA DNA is composed of: DNA is composed of: 2 sugar-phosphate backbones 2 sugar-phosphate backbones 4 types of nitrogenous bases 4 types of nitrogenous bases Adenine Adenine Guanine Guanine Thymine Thymine Cytosine Cytosine

3. DNA base-pairing rules A always pairs with T A always pairs with T G always pairs with C G always pairs with C Provides a way for exact copies of DNA to made → DNA replication Provides a way for exact copies of DNA to made → DNA replication Important to keep genetic code the same when new cells are made! Important to keep genetic code the same when new cells are made!

4. DNA Replication DNA strand is untwisted DNA strand is untwisted Bonds between b.p. are broken Bonds between b.p. are broken Two new strands are made by filling in matching bases one at a time Two new strands are made by filling in matching bases one at a time Result= 2 new identical DNA strands! Result= 2 new identical DNA strands!

5. DNA and the living cell  DNA divided into segments called genes  Humans have over 20,000 genes  Genes provides information for making proteins

6. Genes and Proteins Each gene codes for a unique protein with specialized function in cell Each gene codes for a unique protein with specialized function in cell All cells have the same set of genes All cells have the same set of genes Different kinds of cells use different combinations of genes Different kinds of cells use different combinations of genes Cells only build the proteins they need to do their job! Cells only build the proteins they need to do their job!

7. Functions of proteins in cells General functions: General functions: Enzymes (DNA polymerase) Enzymes (DNA polymerase) Transport proteins (Hemoglobin) Transport proteins (Hemoglobin) Cell signaling proteins (Insulin) Cell signaling proteins (Insulin) Structural proteins (Keratin) Structural proteins (Keratin)

8. Protein synthesis Cell follows TWO step process to build proteins from DNA Cell follows TWO step process to build proteins from DNA Transcription Transcription Making a copy of the DNA (called messenger RNA) and sending that copy to the ribosome Making a copy of the DNA (called messenger RNA) and sending that copy to the ribosome Translation Translation Ribosome use information in the mRNA to assemble the protein Ribosome use information in the mRNA to assemble the protein

9. mRNA vs. DNA Differences between DNA and RNA Differences between DNA and RNA RNA is… RNA is… Single-stranded Single-stranded Different sugar (ribose) Different sugar (ribose) Thymine (T) is replaced by Thymine (T) is replaced by Uracil (U) Uracil (U)

10. Transcription Starts in the nucleus Starts in the nucleus DNA is unzipped DNA is unzipped Copy is made: messenger RNA (mRNA) with complementary bases Copy is made: messenger RNA (mRNA) with complementary bases End result is single-stranded mRNA that travels through the cytoplasm to the RIBOSOME End result is single-stranded mRNA that travels through the cytoplasm to the RIBOSOME

11. Translation Occurs in ribosome (protein building machinery) Occurs in ribosome (protein building machinery) Ribosome reads mRNA sequence 3 letters at a time (codon) Ribosome reads mRNA sequence 3 letters at a time (codon) Each codon codes for a particular amino acid Each codon codes for a particular amino acid 20 possible amino acids 20 possible amino acids Order amino acids are assembled is different for all proteins Order amino acids are assembled is different for all proteins Sequence of a.a. determines shape of protein which determines function Sequence of a.a. determines shape of protein which determines function End result is a specific protein based on the original code! End result is a specific protein based on the original code!

12. Genetic Code