1. DNA The Molecule of Heredity Chapter 11.1

3. DNA - Deoxyribonucleic Acid Contains genetic information (genes) Strands of repeating molecules that make up our chromatin and chromosomes

4. DNA is called the “Blueprint of Life” Why? DNA tells cells which proteins to make The proteins then cause our individual characteristics

5. The Structure of DNA - DNA is in a Double-helix shape -It is double-stranded and wound up like a twisted ladder -2 strands attached to each other Discovery credited to James Watson and Francis Crick. Watson and Crick with DNA Model, 1953.

6. DNA Structure continued  It is a very long molecule made up of repeating subunits called nucleotides

7. 3 Parts of a Nucleotide 1) Phosphate group 2) Simple sugar -DNA has a Deoxyribose sugar -RNA has a Ribose sugar 3) Nitrogenous base -A, T, C, or G

8. 4 Nitrogenous Bases in DNA 1.Adenine 2.Thymine 3.Guanine 4.Cytosine PyrimidinesPurines

9. Special Base Pairing Rules *Adenine pairs with Thymine: A-T T-A *Cytosine pairs with Guanine: C-G G-C

10. The DNA Strand * Bases held together by hydrogen bonds. * Sugar and phosphate are considered backbone

11. What are the proper pairings for the base strands shown: 1.A T C G T T T A C G C G T 2.T G C T A T A C C G T A A 3.C T A G C G A T G T C G T

12. Answers 1.A T C G T T T A C G C G T T A G C A A A T G C G C A 2.T G C T A T A C C G T A A A C G A T A T G G C A T T 3.C T A G C G A T G T C G T G A T C G C T A C A G C A New Strand = Complementary strand Old Strand = Template Strand

13. RNA - ribonucleic acid - Molecules that “read” the DNA and make proteins using the information in DNA -RNA are the worker molecules.

14. 3 ways RNA is different from DNA 1. RNA is single stranded 2. RNA has the sugar ribose (not deoxyribose) 3. RNA has the nitrogen base uracil instead of thymine.

15. RNA nitrogenous bases RNA bases –Adenine –Uracil (in DNA this is thymine) –Cytosine –Guanine –Rules: Same pairing as DNA except a U goes where a T was in DNA –A pairs with U (A-U) and C pairs with G (C-G)

16. RNA base pairing examples IF the DNA strand is A T C G G C A T Then the RNA complement strand is U A G C C G U A IF the DNA is A T A C G T A C G Then the RNA complement strand is U A U G C A U G C

17. Practice Time!

18. Three types of RNA mRNA = Messenger RNA –Carries information from nucleus to cytoplasm (ribosomes in cytoplasm) rRNA = Ribosomal RNA –Make ribosomes which are where amino acids are assembled into proteins tRNA = Transfer RNA –Carries amino acids to the ribosome to be assembled into proteins

19. DNA Replication - 2 from 1 2. During what phase of the cell cycledoes replication occur? 1.Why do cells need to replicate their DNA before dividing?

20. 4 Steps to DNA Replication Step 1:Enzyme (helicase) initiates (starts) replication by unzipping the DNA

21. Step 2:Another enzyme (DNA polymerase) attaches new nucleotides following base pairing rules

22. Step 3: Error Checking As it moves down the strand, the enzyme DNA polymerase: 1.Checks for errors 2.Then fixes them This process is called proofreading Mistake causes a bulge DNA poly. repairs with correct base DNA poly. finds & piece is cut out DNA poly. continues down strand

23. Step 4: Original DNA New DNA 2 Identical copies -1 old strand (template) -1 new strand (complementary) Enzymes twist the new strands (creating the double helix)

24. Steps of DNA Replication 1.Enzyme (helicase) unzips the DNA 2.Enzyme (DNA polymerase) attaches new nucleotides according to base pairing rules 3.DNA polymerase checks for errors and fixes them. 4.End up with two identical daughter DNA strands that enzymes retwist.

25. STOPPING POINT

26. DNA Sequencing Each organisms has a unique sequence of DNA The closer two individuals are related, the more alike their sequences are. What are some ways that we use this knowledge?

27. The Central Dogma

28. DNA Structure and Base Pairs (Adenine) A = T (Thymine) ( Cystosine) C = G (Guanine)