DNA and Protein Synthesis

1. DNA and Protein Synthesis

2. Why are you, YOU? • You are made of basically four types of molecules. • DNA is the molecule that gives instructions to your cells. • 99.9% of human DNA is identical. • Thus, only .1% makes you, YOU!

3. Where is my DNA?

4. DNA is bundled into structures called chromosomes. • If the DNA in a person was stretched out it would reach to the sun and back 600 times. It is an extremely long molecule that coils really tight.

5. What is DNA? • DNA is the genetic information that determines an organism’s traits. • DNA produces proteins • DNA contains the “information for life” • Complete instructions for manufacturing all the proteins for an organism

6. DNA Structure • Very long molecule!!! • DNA is a polymer made of repeating subunits called nucleotides • Nucleotides have 3 parts: 1. Simple sugar = deoxyribose 2. Phosphate group = 1 atom of phosphorus + 4 oxygen atoms 3. Nitrogen base = carbon ring structure that contains one or more atoms of nitrogen

7. Nitrogen Bases • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T) • In DNA there are four possible nucleotides, each containing one of these four bases.

8. Purines and Pyrimidines

9. How do the nitrogen bases bind?

10. DNA Bonding Order • Phosphate group of one nucleotide bonds to the deoxyribose sugar of an adjacent nucleotide • Form the backbone of the chain • Nitrogen bases bond in complementary base pairs : • Adenine (A) bonds with Thymine (T) • Guanine (G) bonds with Cytosine (C)

11. DNA Structure

12. Double Helix • In 1953, James Watson and Francis Crick proposed that DNA is made of two chains of nucleotides joined together by the nitrogen bases. • Nitrogen bases are held together by weak hydrogen bonds • Shaped like a long zipper that is twisted = Double Helix

13. Francis Crick James Watson

14. 1953 Nobel Prize, 1962

15. Double Helix • Rosalind Franklin and Maurice Wilkins worked together performing X-ray diffractions of the DNA model • Photographs revealed that DNA was a tightly coiled helix • Chargaff discovered that #A = #T & #C=#G

18. DNA Structure

20. DNA Replication • DNA replication produces two molecules from one • Each strand serves as a pattern to make a new DNA molecule. • Begins as an enzyme breaks the hydrogen bonds between the nitrogen bases. • Unzips the strand

21. DNA Replication • When the DNA needs to be copied so that the cell can divide the double helix starts to unwind and unzip down the hydrogen bonds.

22. Replication Continued • Nucleotides that are floating free in the surrounding medium bond to the single stands by base pairing. • Another enzyme bonds these new nucleotides into a chain. • Each new strand formed is a complement of one of the original • DNA Replication Animation

24. We will now CREATE a model of DNA!

25. Proteins and Enzymes • DNA produces proteins • Proteins form key cell structures and regulate cell functions • Enzymes are proteins that control chemical reactions • Examples: • Breaking down glucose molecules in cellular respiration • Digesting food • Making spindle fibers during mitosis

26. Central Dogma of BiologyDNA → RNA → Protein

27. Transcription • DNA → RNA • mRNA, rRNA, tRNA • Purpose: to send instructions from nucleus to cytoplasm

28. Translation • RNA → Protein • @ Ribosome • Purpose: Proteins follow the instructions and do all the jobs of the cells / organisms. • Proteins: • 20 Amino Acids • Coded by 3 Nucleotides in RNA, called codons

29. Central Dogma

30. RNA • RNA is a single strand • The simple sugar in RNA is ribose • Nitrogen bases in RNA: • Adenine • Guanine • Cytosine • Uracil (bonds with adenine)

31. 3 Differences between DNA & RNADNA RNA Single strand Double helix Thymine base Uracil base Ribose sugar Deoxyribose sugar

32. Types of RNA • Messenger RNA (mRNA) = brings information from the DNA in the nucleus to the cell’s cytoplasm • Ribosomal RNA (rRNA) = ribosomes that clamp onto the mRNA and use its information to assemble the amino acids in the correct order. • Transfer RNA (tRNA) = transports amino acids to the ribosome to be assembled into a protein.

33. Transcription • Similar to DNA replication, but the result is the formation of one single-stranded RNA molecule (mRNA) • Process • Enzyme unzips the DNA molecule • Free RNA nucleotides pair with complementary DNA nucleotides • When pairing is complete, mRNA molecule breaks away and the DNA rejoins the original strand

34. Genetic Code • Three nucleotides codes for one amino acid • Each set of nitrogen bases in mRNA represent and amino acid = CODON • The order of the nitrogen bases in mRNA will determine the order of amino acids in a protein • 64 combinations are possible (43) • Some codons do not code for amino acids; they provide instructions for assembling proteins • Example: Start and Stop signals

36. Genetic Code Continued • UAA, UGA, UAG = stop codons • Protein production ends at this point • AUG = start codon + amino acid methionine • More than one codon can code for the same amino acid • Genetic code is universal • Cell Activities

37. Translation • Converts mRNA into the amino acids that make up proteins • Translation takes place at the ribosomes in the cytoplasm • tRNA molecule attaches to only one type of amino acid of mRNA • tRNA makes an anticodon of mRNA

38. Translation Process • tRNA brings the first amino acid to the mRNA strand attached to the ribosome • Anticodon forms a temporary bond with the codon of mRNA • Ribosome slides down the mRNA chain to the next codon, and tRNA brings another amino acid • First amino acid detaches from the mRNA in the ribosome • Process continues until a stop codon is reached

39. Introns vs. Exons • Most of DNA is made up of segments that are NOT expressed • Introns are segments of genes that are not expressed (aka DNA Junk) • Exons are segments of genes that are expressed • When RNA is made, introns and exons are copied, then the introns are removed from the RNA while it is still in the nucleus • Role of introns in evolution? • Very small changes in gene expression could have dramatic effects in gene expression

40. Genetic Mutations-Latin meaning “to change”

41. Genetic Mutations • Any change in the DNA sequence is called a mutation. • Mutations can effect reproductive cells • Mutations can effect somatic (body) cells • Example = CANCER • Types of Mutations: • Point mutation • Frameshift mutation • Insertions or Deletions • Chromosomal mutation

42. Point Mutation • A change in a single base pair in DNA • Example 1: • THE DOG BIT THE CAT. • THE DOG BIT THE CAR. • Example 2: • THE DOG BIT THE CAT. • THE DOG HIT THE CAT. • Can change the entire structure of a protein, and effect the shape of the protein.

43. Frameshift Mutation • A single base pair in DNA is deleted or inserted. • Every codon after the deleted base would be different. • Entire codons can be inserted or deleted • Example: • THE DOG BIT THE CAT. • THE DOB ITT HEC AT.

44. Chromosomal Mutations • Five kinds of chromosomal mutations: • Deletions occur when part of a chromosome is left out. • Insertions occur when a part of a chromatid breaks off and attaches to its sister chromatid. • Inversion occur when part of a chromosome breaks off and is reinserted backwards. • Translocation occur when part of one chromosome breaks off and is added to a different chromosome. • Nondisjunction – failure of homologous chromosomes to separate during meiosis

45. Mutations Deletion Duplication Inversion Translocation

46. Causes of Mutations • Spontaneous: • Mistake in base pairing during DNA replication or protein synthesis • Errors in cell division • Mutagen – agent that causes DNA change • High energy radiation • X-rays, UV light • Chemicals • Dioxins, asbestos, benzene, cyanide, formaldehyde • High temperatures Mutagen Video

47. What is a karyotype? • Errors from nondisjunction can be determined by performing a karyotype • Make a karyotype… • Cells collected from unborn child through amniocentesis (skin cells obtained) • Blood sample taken from individual

48. #1 Sample Karyotypes #2

49. Sample Karyotypes #3

50. Sample Karyotypes #4