Introduction to DNA

1. Introduction to DNA Structure

2. Vocabulary DNA (Deoxyribonucleic Acid) – A nucleic acid that contains a deoxyribose sugar. Is a long molecule that is made up of units called nucleotides Nucleotides – Monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. The THREE basic units of DNA

3. DNA • DNA contains the genetic code of an organism, with traits expressed through proteins made by cells • DNA can be found in the nucleus and mitochondria.

4. 2 rings 1 ring

5. Double Helix • DNA resembles a twisted ladder, with sugars and phosphates on sides, and nitrogen bases as rungs

6. 5’ has a free Phosphate 3’ end has a free Sugar

9. Nitrogen Bases • The nitrogen bases of DNA from complementary base pairs with adenine pairing with thymine, and cytosine pairing with guanine • The nitrogen bases spell out a coded message.

10. Name the three parts of a nucleotide. Find the complimentary strand for the following DNA strand: ATTTCGTGCAGA ?????????????? 3. Do purines of pyrimidines have two rings? Quiz: DNA 4. What does a double helix look like? 5. What does DNA stand for? • Degraded Nucleic Acid • Deoxyribose Nitrogenous Acid • Deoxyribonucleic acid 6. What was Rosaline Franklin known for? • Finding out the structure of DNA • Taking pictures of DNA with a x-ray • Discovering the existence of DNA 7. What are Watson and Crick known for? • Finding out the structure of DNA • Taking pictures of DNA with a x-ray • Discovering the existence of DNA

11. Introductions to DNA Replication

12. Replication • DNA replication happens in the Synthesis phase of the cell cycle • Happens BEFORE mitosis Replication

13. DNA Replication • When DNA is replicated or copied, it results in two IDENTICAL strands. • Replication happens in three simple steps: • The two original strands of DNA are separated by helicase • DNA Polymeraseadds complimentary nucleotides to each strand. • Two DNA molecules form that are identical to the original.

14. Step 1: DNA Separates • The DNA helix unwinds with the help of enzymes called DNA helicases. • Nucleotide bases separate at an area called the replication fork.

15. Step 2: DNA Polymerase adds nucleotides New Strands forming • At the replication fork, DNA Polymerase move along each DNA strand and add complimentary nucleotides. • Adenine with thymine • Cytosine with Guanine • Two new strands begin to form.

16. Step 3: Two DNA Molecules form • DNA polymerase continues adding nucleotides until all the DNA has been copied. • DNA polymerase detaches and two new identical DNA molecules are left.

17. DNA Polymerases other role… • Because errors can occur in DNA replication, DNA polymerase also has a role in fixing the new DNA strands. • DNA polymerase fix mismatched nucleotides

18. DNA Replication in Eukaryotes • Eukaryotes have one long DNA strand for each chromosome • semi conservative model (new double helix has 1 parent strand + 1 new daughter strand) • replication fork Parent strand Daughter strand

19. DNA REPLICATION in Prokaryotes • Prokaryotes have one circular DNA • replication fork

20. PASTA DNA LAB • Follow Procedure I to make a model of DNA. • Follow the directions EXACTLY the same EXCEPT instead of tying the noodles on string, GLUE THEM on to notebook paper. • In Procedure two, make a model of DNA “unzipping” or separating on another piece of paper. • The show 2 identical DNA strands that were made. • They should look EXACTLY like the first DNA strand.

21. Pasta DNA • Wheels- Sugar • Noodle-Phosphate • Paper clip- Bases

22. From DNA to Protein Transcription

23. Making Proteins… • …involves a series of steps. • Transcription & Translation • mRNA is made in transcription. • Protein is made in translation.

24. RNA • RNA differs from DNA in three ways: • Single stranded • Has uracil instead of thymine nitrogen bases • Contains ribose sugar instead of deoxyribose in its backbone.

25. Transcription in 3 easy stepsStep 1 • Transcription starts when RNA polymerase binds to a specific DNA sequence that tells cell to START transcription. • Remember, A,T,C, and G “spell” out messages. START

26. Step 2 • Next, the RNA polymerase unwinds and separates the DNA.

27. Step 3 • Last, RNA polymerase adds complimentary RNA nucleotides to the DNA strand. • The polymerase adds: • cytosine to guanine and guanine to cytosine • adenine to thymine BUT uracil to adenine.

28. Why make Messenger RNA? • When a cell needs a protein, mRNA is created. • mRNA carries instructions for building a protein and delivers it out side of the nucleus. Messenger RNA

29. ACTIVITY! ^_^ • Your objective is to take the following DNA strands and transcribe them into RNA. • Materials: Pipe cleaners and colored beads. • Green: Adenine; Yellow: Guanine; Red: Thymine; Blue: Cytosine; White: Uracil. • Procedure: Transcribe the SECOND STRAND of each of the following DNA sequences. • Make your DNA and RNA using the pipe cleaner given and the colored beads. • Show me your RNA strand. If it is correct then turn into me your RNA sequences written down on paper. Return the beads and pipe cleaners • DNA sequence one Strand one: ATGCTGAAG Strand two: TACGACTTC • DNA sequence three Strand one: TATCGTAGT Strand two: ATAGCATCA • DNA sequence two • Strand one: CGCTTAAAC • Strand two: GCGAATTTG • DNA sequence four • Strand one: ATGCAATAG • Strand two: TACGTTATC

30. From DNA to Protein Translation

31. Vocabulary • Ribosomal RNA are part of the structure of ribosomes. • They hold the mRNA and two tRNAs in place during translation • tRNA molecules are single strands of RNA that carry a specific amino acid with them. • Amino acids: make PROTEINS

32. Vocabulary • Codons: instructions written as three nucleotide sequences. • Each codon corresponds to an amino acid or start or stop signal. Ex: GUA  Valine UUC Phenylalanine

33. To build a protein… • …we must move on to our next step that moves our RNA out of the nucleus and into the cytoplasm.

34. Translation • mRNA moves into the cytoplasm where it binds with a rRNA, and a tRNA carrying an amino acid. • The codon is ready to receive the next tRNA and its amino acid

35. Peptide bond • Once mRNA is holding two tRNAs, each carrying specific amino acids, enzymes form peptide bonds between the two amino acids. • The tRNA in the first site prepares to detach, leaving behind the amino acid.

36. Another tRNA fills in the empty site. • This process repeats until a STOP codon is reached (UAG, UAA, or UGA). • The amino acid chain is release, forming into a new protein.

37. Amino acids form protein. Transcription