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DNA/RNA & Molecular Basis of Evolution

DNA/RNA & Molecular Basis of Evolution. ASTR 1420 Lecture 4 Sections 5.2, 5.4. Organic Building Blocks. Cells. Typical Eukaryotic Cell. All living organisms are made of cells Adult human body have 10-50 trillion cells!. Components of Cell.

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DNA/RNA & Molecular Basis of Evolution

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  1. DNA/RNA&Molecular Basis of Evolution ASTR 1420 Lecture 4 Sections 5.2, 5.4

  2. Organic Building Blocks

  3. Cells Typical Eukaryotic Cell • All living organisms are made of cells • Adult human body have 10-50 trillion cells!

  4. Components of Cell • Carbohydrates (= carbs) : providing energy to cells and make cellular structures  sugars, starches, cellulose, etc. • Lipids (aka fats) : store energy, make cell membranes • Proteins : versatile, essential molecules of cells • Nucleic acids : handling heritable information of cells – DNA and RNA

  5. DNA  Proteins • All Earth life have DNA, and DNA is the backbone of heredity. • Heredity  DNA replication • function of DNA (genes)  protein synthesis • What’s protein? • organic compound made of amino acids in a folded chain • essential part of organisms and participate in every process within cells • enzymes involved in matabolism • make cell stucture • cell signaling, immune responses, etc.

  6. http://www.youtube.com/watch?v=qy8dk5iS1f0 DNA structure

  7. http://www.youtube.com/watch?v=hfZ8o9D1tus DNA replication

  8. http://www.youtube.com/watch?v=XO-2Z933AzM Protein synthesis

  9. RNA world? • In the beginning of Earth life, the very first life could not be based on DNA. DNA is way too complicated to be created by mere “lucky” chemical reaction. • early life must have used a simpler molecule (e.g., RNA) • or, DNA was introduced externally?!? Although we do not expect DNA or RNA to appear in life on other worlds, molecules with similar function are well expected!

  10. Amino Acids • Most important monomer! • Basic building blocks of proteins, nucleotides, and sugars • Typically, few hundred amino acids form a protein polymer. There are about 70 different amino acids in the nature, but only ~20 are used in living organisms. A strand of amino acids, part of a protein

  11. Monomer/Polymer • Glycogen: the carbohydrate that animals use to store energy is a polymer made of glucose molecule contains 22 atoms Most life forms consist of small number of simple molecule types called monomers, which can join together in a repetitive sequence to become larger and more complex molecules called polymers. glucose

  12. Chirality of Amino Acids • Chirality (handedness) For a given amino acid, there are two geometricalshapes: left-handed & right-handed • In non-biological environ: two types are equally found • In living organisms: only left-handed amino acids are found! • All Earth life forms were originated from an ancestral life using only left-handed amino acids!

  13. Genes • a distinct portion of DNA strand representing any single function (e.g., instruction for one protein)

  14. Small difference in genes • Different human races • Any possible distinct genetic differences are now disappeared by inter-racial breed. • Genetic difference b/w races < b/w two individuals from one race! • Astrobiological Implication? • Small genetic difference  huge difference (e.g., Chimpanzee vs. Human) ; Chimpanzee and human share 98% of the same genes • Is advanced intelligence an inevitable evolutionary outcome?

  15. Genetic code : a set of rules for reading DNA Codes for most amino acids really depend on just two letters  in the past, genetic codes were two letter based… • Genetic “words” consist of three DNA bases in a row. For the purpose of protein building, each word represents either a particular amino acid or “start reading” or “stop reading”. • Genetic code is same for nearly ALL living organisms on Earth! common ancestor of all life on Earth!

  16. Mutation • Replicating the whole ~3 billion bases for human DNA takes only a few hours • About 1 replication error in billion chances • wrong base • deleted base • extra base • etc. • Most of these errors have no effect Why? about 95% of human DNA bases are “non-coding DNA” Most significant change is from “deleted base”. • Due to this “error”, every individual living organism differ each other. • Mutation = molecular engine of the evolutionary adaption! • Any change in the base sequence of DNA

  17. Sickle-cell disease • Just one base change in one gene (Adenine  Thymine) • Most mutations are harmful, but occasional good mutations are being picked up by “natural selection”

  18. Another evidence of the common ancestor • ATP (Adenosine TriPhosphate). • Cells recyleATP. • The ATP molecule gives up energy when it splits into ADP and a phosphate group. • ATP/ADP are like battery • ATP : fully charged • ADP : fully discharged • There are many other possibilities of different molecular pairs (i.e., different batteries), but all Earth life use ATP as the energy reservoir. common ancestor of all Earth life.

  19. In summary… Important Concepts Important Terms amino acids / proteins chirality genes, genetic code mutation • Common ancestor of all Earth Life (chirality of amino acid, common genetic code, and use of ATP among all living organisms on Earth) • Some non-DNA based life forms in the beginning? • DNA replication • Chapter/sections covered in this lecture : 5.2 & 5.4

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