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DNA Structure

DNA Structure. What is it?. What is DNA? Deoxyribosenucleic Acid Located in the nucleus of a cell DNA is a nucleic acid DNA is made of nucleotides. Nitrogen Bases. Made of three things Phosphate Groups Deoxyribose sugar Nitrogen Base. Nitrogen Bases. Nitrogen Bases

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DNA Structure

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  1. DNA Structure

  2. What is it? • What is DNA? • DeoxyribosenucleicAcid • Located in the nucleus of a cell • DNA is a nucleic acid • DNA is made of nucleotides

  3. Nitrogen Bases • Made of three things • Phosphate Groups • Deoxyribose sugar • Nitrogen Base

  4. Nitrogen Bases • Nitrogen Bases • Two bases are called purines (larger) • Adenine (A) • Guanine (G) • Two bases are pyrimidines (smaller) • Thymine (T) (only found in DNA) • Cytosine(C)

  5. Nitrogen Bases • Chargaff’s Rule • Adenine only pairs with Thymine • Guanine only pairs with Cytosine • Therefore, for every A there is a T and for every G there is a C

  6. Structure • The DNA has a characteristic double helix • Double because there are two sides • Helix because it forms a spiral • Resembles a twisted ladder

  7. The structure was discovered by Watson and Crick • Contributions were made by Pauling, Franklin, and Wilkins

  8. Structure • The nitrogen bases are held together by Hydrogen Bonds

  9. Hydrogen Bond • Hydrogen bonds are attractions between hydrogen atoms on 1 molecule and oxygen atoms on another. Like a magnet • Very weak bonds

  10. Sequence • How the nitrogen bases are arranged are • Unique to the species • Unique to the individual • The more similar the sequence of DNA is, the more closely related the two species are

  11. Warmup 2/06 • What is the structure of DNA? • What are our 4 nucleotides? • Describe Chargaff’s Rule. • What type of bond holds the two sides of DNA together?

  12. Warmup 2/07 • What are the 3 parts of a nucleotide? • Where is the DNA found? • Why does the DNA stay in this structure? • What are 2 reasons for why organisms look different from each other even though all of our DNA is made of the same 4 nucleotides?

  13. DNA Replication

  14. Making A Copy • Replication: process of making an exact copy

  15. Reasons for DNA Replication • Start Cell Division • Tissue growth and/or repair

  16. Steps of DNA Replication • We use the semi-conservative model • You will use the original piece of DNA as a template (half the old DNA will be used in the new DNA strand) • The right strand will form one new piece of DNA • The left strand will form another new piece of DNA

  17. Remember that A pairs with T and C pairs with G • Each strand is complementary to the other (it matches)

  18. Helicase • Step 1: DNA unwinds • Uses an enzyme called helicase • You need the weak Hydrogen Bonds so you can pull the DNA apart easier

  19. Making our DNA longer • Step 2: Add new nucleotides to the original DNA strands • Proteins called DNApolymerases help add the new nucleotides

  20. Models of DNA Replication

  21. Example of Replication • Example: • Original piece of DNA: A T G C T G T T A • Complementary piece:

  22. Warmup 2/10 • Which enzyme splits DNA? • What model is used to describe the process of DNA replication? • What does template mean?

  23. Differences between DNA and RNA Making A Protein

  24. RNA Structure • Ribonucleic Acid • Made of 3 parts • Phosphate group • Ribose sugar • Nitrogen base

  25. RNA Structure • Only has one strand • Nitrogen Bases • Guanine (G) • Cytosine (C) • Adenine (A) • Uracil (U) (only found in RNA)

  26. Types of RNA • Types of RNA • Messenger RNA (mRNA): complementary copy of DNA • Ribosomal RNA (rRNA): part of what makes a ribosome • Transport RNA (tRNA): transports amino acids to the ribosome

  27. Warmup 2/11 • What are the 3 major differences between DNA and RNA? • What is the sugar found in RNA? • How do DNA and RNA work together?

  28. Transcribing RNA • Transcription: Process of making mRNA • Steps of Transcription • RNA Polymerase binds to the DNA • DNA unwinds only where the polymerase is bound

  29. RNA polymerase adds RNA nucleotides together that form a complimentary copy of the DNA • C pairs with G and A pairs with U • When the mRNA is done being made it separates from the DNA and leaves the nucleus

  30. Example • Example • Original DNA strand: G T C A G T A G T T G C • mRNA strand:

  31. Warmup 2/17 • What is made during transcription? • What are the steps of transcription? • What are 2 differences between DNA and mRNA? • Where does transcription happen?

  32. Translation • Translation (mRNA  Protein) • Process of turning a mRNA strand into a protein

  33. Translation • What is a protein? • Chains of amino acids linked together • DNA encodes the instructions to make proteins • DNA needs to be changed into RNA to make the protein

  34. mRNA is read with a ribosome • The ribosome “reads” the mRNA 3 bases at a time • These 3 bases are called codons. • Each codon codes for 1 amino acid

  35. Practice Problems • Write out the mRNA acodons to the DNA codons below • AAT • CGA • TAC • GAT

  36. tRNA brings the amino acids to the ribosome • Ribsome binds the amino acid to other amino acids with a peptide bond • The tRNA forms a complement to the mRNA codon • Called an anti-codon

  37. Practice Problems • Write out the tRNA anti-codons to the mRNA codons below • UUA • GCA • AUG • CUA

  38. You use a codon chart to determine which amino acid bonds to the codon

  39. Practice Problems • Use the codon chart to match the amino acids to the codons • UUA • GCA • AUG • CUA

  40. Warmup 2/18 • What is used to put the amino acids together? • What is the 3 letter code found on tRNA called? • What is the name of the process that creates proteins? • What is a protein?

  41. Mutations

  42. Mutations • Change in the DNA of an individual • Can be caused by • Radiation • Chemicals • Spontaneous • If it happens in the gametes (sperm or egg cells), it will be passed on to the children

  43. Types of Mutations • Point Mutations • Change in 1 nucleotide base pair in the DNA sequence • EXAMPLE • TTT GGG CCC AAA: Original • TTT AGG CCC AAA: Mutated

  44. Types of Mutations • Frameshift Mutations • Causes the codon reading frame to get moved up or down one spot • Insertion: when a new nucleotide gets put into the sequence • TTT GGG CCC AAA: OriginalTTT GGG ACCCAA A: Mutated

  45. Frameshift Mutations EXAMPLE • Deletion: when 1 nucleotide gets removed from the sequence • TTT GGG CCC AAA: OriginalTTT GGC CCA AA: Mutated

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