1. Unit 6: DNA & Protein Synthesis Ch. 28: DNA—Life’s Code DNA = Deoxyribonucleic Acid

2. Describing DNA Who first described DNA? –James Watson & Francis CrickJames Watson & Francis Crick What shape did they use to describe DNA? –double helix

3. DNA is a Polymer… What is the monomer that repeats to make DNA? –nucleotide

4. What are the parts of a nucleotide? phosphate group sugar nitrogenous base –4 kinds: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) adenine, thymine, guanine, cytosine

5. A Model of DNA Is a DNA molecule single- stranded or double stranded? –double-stranded What parts make up the strands? –“backbone”/sides sugars & phosphates –“rungs”/steps nitrogenous bases –Always paired as: »A - T »G - C DNA Structure Video

6. Where is DNA found in eukaryotic cells? DNA is contained in chromosomes (chromatin) within the nucleus sugar-phosphate “backbone” & nitrogenous base “rungs”

7. DNA Replication What is another word for replication? –copying Why must DNA replicate? –so when cell divides, each new cell gets a copy of DNA http://www.stolaf.edu/peo ple/giannini/flashanimat/m olgenetics/dna-rna2.swf

8. DNA Replication When does DNA replicate? –before the cell divides (before mitosis) Where does DNA replicate? –inside the nucleus

10. 1. DNA molecule unzips between bases forming two “parent strands” What are the steps in DNA replication?

11. 2. The “parent” strands act as templates (guides)… –“new” nucleotides are paired up with the complementary base on the “parent” strand forming a complementary daughter strand –ex. “G” pairs with “C” What are the steps in DNA replication? T C

12. 3. Now, there are 2 exact copies of the original DNA molecule. –& when the cell divides, each “new” daughter cell gets a copy What are the steps in DNA replication?

13. DNA Replication Video T C What are the steps in DNA replication?

14. Let’s Practice… Predict the next base…

15. Let’s Practice… Finish the replications…

17. Deoxyribonucleic Acid vs. Ribonucleic Acid DNARNA sugar = deoxyribose sugar = ribose double stranded single stranded CANNOT leave nucleus Can move between nucleus & cytoplasm N bases = adenine, thymine, guanine, cytosine N bases = adenine, uracil, guanine, cytosine

18. The DNA Code & Protein Synthesis What is a gene? –a section of DNA that codes for the synthesis (making) of a specific protein Which part of DNA actually carries the code? –the nitrogen bases & their order –If the sequence is changed  the amino acid (usually) changes  & the protein made (usually) changes.

19. So, the big question is… –How does the DNA code in a cell’s nucleus get to the ribosomes where proteins are synthesized? transcription & translation The DNA Code & Protein Synthesis

21. Transcription What is transcription? –DNA code is “transcribed”/copied into mRNA codons When does transcription happen? –when a protein is needed Where does transcription happen? –in the nucleus

22. Transcription What does transcription make? –A single-stranded messenger RNA (mRNA) made from instructions/order of the bases in the DNA What are the steps in transcription? 1.DNA unzips 2.free RNA nucleotides pair w/ exposed bases on DNA until “stop codon” is reached 3.mRNA separates from DNA & moves out of nucleus http://www.stolaf.edu/people/ giannini/flashanimat/molgen etics/transcription.swf

23. mRNA What is a codon? –3 consecutive bases on mRNA that codes for a particular amino acid Some amino acids have more than one codon –How can we figure out the amino acid coded for by a codon? »a codon chart

24. mRNA Codons & Amino Acids

27. Translation What is translation? –process of making proteins from mRNA codons (with help of tRNA/ transfer RNA anticodons & ribosomes) When does translation occur? –when mRNA from the nucleus joins with ribosomes Where does translation happen? –in the cytoplasm

28. What are the steps in translation? 1.anticodon on tRNA: joins with complementary mRNA codon carries amino acid specified by the codon on mRNA to ribosome 2.Amino acids line up & bond to form protein http://www.stolaf.edu/people/giannini/fl ashanimat/molgenetics/translation.swf Translation

29. tRNA anticodon DNA codon mRNA codon transcriptiontranslation mRNA codon

32. Let’s Practice… What would the mRNA strand made during transcription look like?

33. What amino acids would be coded for using this mRNA?

34. What would the anticodons on the tRNA be for each amino acid?

35. Let’s Practice… Given the DNA sequence below, determine the: 1.mRNA codon sequence 2.amino acids that would be coded for by each codon 3.anticodons on each tRNA which allowed it to “bring” that amino acid (using the mRNA codons) DNA = TAC CCA GAT CCG ACT mRNA codon = amino acid = anticodon (on tRNA) =

36. Mutations What are mutations? –mistakes/changes in a gene on a chromosome can occur spontaneously during replication can be caused by mutagens (such as radiation, high temperatures, or chemicals) often corrected, but not always –once occurs, copied as if correct –can cause different protein

37. Types of Mutations What are the 3 types of mutations? 1.deletion What happens in a deletion mutation? –a nucleotide (base) is left out »causes “frame shift” ~moves nucleotides after the deletion to the left causing a different protein to be formed

38. 2.insertion What happens in an insertion mutation? –a nucleotide (base) is added in »causes “frame shift” ~moves nucleotides after the insertion to the right causing a different protein to be formed Types of Mutations

39. 3.point What happens in a point mutation? –one nucleotide (base) is replaced by another »does not cause “frame shift” ~sometimes amino acid & protein can be the same

40. Sickle Cell Mutation What does the sickle cell mutation do? –affects hemoglobin What type of mutation causes sickle cell? –A point mutation changes one amino acid –changes the protein