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2.7 Gene Expression

2.7 Gene Expression. DNA. DNA. DNA stands for Deoxyribose nucleic acid DNA is a very large molecule It is made two strands of molecules which are twisted together in the shape of a Double Helix. The two strands of DNA are called the backbone

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2.7 Gene Expression

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  1. 2.7 Gene Expression

  2. DNA

  3. DNA • DNA stands for Deoxyribose nucleic acid • DNA is a very large molecule • It is made two strands of molecules which are twisted together in the shape of a Double Helix. • The two strands of DNA are called the backbone • Each strand is made up of alternating molecules of sugar and phosphate

  4. DNA • The strands are joined by molecules called nitrogen bases. • DNA is described as a large polymer. • A polymer is made up of repeating units called monomers. • The monomers of DNA are called nucleotides • Nucleotides are made up of a sugar, phosphate and base.

  5. Phosphate Group O O=P-O O 5 CH2 O N Nitrogenous base (A, G, C, or T) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide

  6. Bases Weak hydrogen bonds hold the bases together.

  7. A or G T or C Nitrogenous Bases • Double ring PURINES Adenine (A) Guanine (G) • Single ring PYRIMIDINES Thymine (T) Cytosine (C)

  8. 3 H-bonds G C Base-Pairings • Purines only pairwith Pyrimidines • Three hydrogen bonds required to bond Guanine & Cytosine

  9. A T Two hydrogen bonds are required to bond Adenine & Thymine

  10. 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 DNA

  11. It is called Deoxyribose Sugar • Deoxy means one oxygen atom less (than RNA) • Ribose is a 5 Carbon Sugar Molecule • The carbon atoms are numbered in a particular way from (1-5, see diagram above)

  12. Phosphate

  13. Functions of DNA • Describe the functions of DNA • DNA contains the Genetic Code (in its base sequences to make proteins). • DNA is able to replicate itself and therefore pass on the genetic code from one generation to the next.

  14. Antiparallel DNA

  15. RNA RNA stands for Ribonucleic Acid RNA is called a Nucleic Acid RNA and DNA are both involved with making proteins.

  16. Functions of RNA • Together with DNA, makes proteins. • Contains the genetic code in some viruses eg. HIV (these do not have DNA)

  17. Comparison of DNA and RNA

  18. Gene

  19. GENE • A gene is a section of DNA on a chromosome, that has a specific base sequence that codes for a protein.

  20. PROTEINS

  21. video's for 2.7\How Genes Work Hand-Me-Down Genes Series - DNA and Proteins Part 1 - How Genes Work.wmv

  22. Basic Gene Protein A gene on DNA codes for a particular protein, which, together with other compounds/molecules makes up a characteristic eg. Eye Colour.

  23. Name the following? A Cytoplasm Ribosome B Nucleus C

  24. Cell Organelles

  25. Cell Organelles

  26. DNA • http://www.youtube.com/watch?v=qy8dk5iS1f0

  27. DNA Structure & Purpose. • DNA is a double helix, with a phosphate-sugar backbone and bases paired by hydrogen bonds (Adenine with Thymine and Cytosine with Guanine). • It holds the genetic code in it’s base order. DNA is found in the nucleus of eukaryotic cells • (NB. It is also in the cytoplasm of prokaryotic cells) but eukaryotic vsProkaryote comparisons are not needed at Level 2.

  28. THE GENETIC CODE

  29. Amino Acids

  30. NUCLEIC ACIDS • These are the biochemical macromolecules involved with the transmission of inherited information. There are two main types: DNA& RNA. Nucleic acids are polymers made up of many units called monomers.

  31. AMINO ACIDS

  32. Redundancy vs Degeneracy • Redundancy refers to the many ways that one Amino Acid can be coded for by various codon combinations. • Whereas Degeneracy refers to the third position in the codon and that in most cases, if it were to change, the Amino Acid coded for would still be the same. • Both redundancy and degeneracy protect against mutations, because most times the Amino Acid sequence and therefore protein will remain un affected.

  33. PROTEINS

  34. Hydrogen Bonds Disulfide Bonds

  35. Proteins • Why can proteins be described as an amino acid chain and as a polypeptide chain? • What are some of the functions of proteins?

  36. Protein Synthesis –simple overview of mRNA and tRNA • http://www.metacafe.com/watch/319359/human_genome/

  37. Gene Expression outline This unit is entitled Gene Expression. It covers some basic aspects of how the information encoded in our genome (by the order of nucleic bases), are expressed. Remember a gene codes for a specific protein. So the basic process of going from Gene  Protein What is needed and how it can be influenced will be covered.

  38. Extract from Campbell & Reece

  39. 1. Copying of Genes • This is transcription when a section of DNA is copied to RNA. • This occurs in the nucleus.

  40. 1. Copying of Genes What is RNA? • It is a single stranded Nucleic Acid. • Bases used (A, G, C & U instead of T) • Small & Short (one gene only) • Unstable (easily broken down & bases recycled) • There are three types of RNA • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

  41. 1. Copying of Genes Transcription: • Occurs in the Nucleus. • DNA is unzipped by Helicase • RNA Polymerase then uses the DNA as a template to make a complementary strand of mRNA. • Once the gene has been copied, the mRNA can then move outside the nucleus.

  42. SEM The banding on this chromosome is thought to correspond to groups of genes. Regions of chromosome puffing are occur where genes are being transcribed into mRNA. A polytene chromosome showing localized regions that are uncoiling to expose their genes (puffing) to allow transcription. Polytene chromosomes are giant chromosomes formed by multiple DNA replications.

  43. Transcription • http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

  44. Translation • http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf simple • http://207.207.4.198/pub/flash/26/transmenu_s.swf complex

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