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Basic Molecular Biology

Basic Molecular Biology

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Basic Molecular Biology

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  1. Basic Molecular Biology Many slides by Omkar Deshpande

  2. Overview • Structures of biomolecules • Central Dogma of Molecular Biology • Overview of this course • Computer scientists vs Biologists

  3. Human Genome Program, U.S. Department of Energy, Genomics and Its Impact on Medicine and Society: A 2001 Primer, 2001

  4. Watson and Crick

  5. Nucleic acids (DNA and RNA) • Form the genetic material of all living organisms. • Found mainly in the nucleus of a cell (hence “nucleic”) • Contain phosphoric acid as a component (hence “acid”) • They are made up of nucleotides.

  6. Nitrogenous Base Nitrogenous Base Phosphate Group Phosphate Group Sugar Sugar Nucleotides

  7. A T G C C G G C A T C G A T G C DNA A = T G = C

  8. The gene and the genome • Genome = The entire DNA sequence within the nucleus. • The information in the genome is used for protein synthesis • A gene is a length of DNA that codes for a (single) protein.

  9. How big are genomes?

  10. Repeats • The DNA is full of repetitive elements (those that occur over & over & over) • There are several type of repeats, including SINEs & LINEs (Short & Long Interspersed Elements) (1 million just ALUs) and low complexity elements. • Their function is poorly understood, but they make problems more difficult.

  11. Central dogma ZOOM IN tRNA transcription DNA rRNA snRNA translation POLYPEPTIDE mRNA

  12. Transcription • The DNA is contained in the nucleus of the cell. • A stretch of it unwinds there, and its message (or sequence) is copied onto a molecule of mRNA. • The mRNA then exits from the cell nucleus.

  13. A A T G G C C C G G G C A A T C C G U A T G G C DNA RNA A = T G = C T  U

  14. More complexity • The RNA message is sometimes “edited”. • Exons are nucleotide segments whose codons will be expressed. • Introns are intervening segments (genetic gibberish) that are snipped out. • Exons are splicedtogether to form mRNA.

  15. Splicing frgjjthissentencehjfmkcontainsjunkelm thissentencecontainsjunk

  16. Key player: RNA polymerase • It is the enzyme that brings about transcription by going down the line, pairing mRNA nucleotides with their DNA counterparts.

  17. Promoters • Promoters are sequences in the DNA just upstream of transcripts that define the sites of initiation. • The role of the promoter is to attract RNA polymerase to the correct start site so transcription can be initiated. 5’ 3’ Promoter

  18. Promoters • Promoters are sequences in the DNA just upstream of transcripts that define the sites of initiation. • The role of the promoter is to attract RNA polymerase to the correct start site so transcription can be initiated. 5’ 3’ Promoter

  19. Transcription – key steps DNA • Initiation • Elongation • Termination DNA + RNA

  20. Transcription – key steps DNA • Initiation • Elongation • Termination

  21. Transcription – key steps DNA • Initiation • Elongation • Termination

  22. Transcription – key steps DNA • Initiation • Elongation • Termination

  23. Transcription – key steps DNA • Initiation • Elongation • Termination DNA + RNA

  24. Genes can be switched on/off • In an adult multicellular organism, there is a wide variety of cell types seen in the adult. eg, muscle, nerve and blood cells. • The different cell types contain the same DNA though. • This differentiation arises because different cell types express different genes. • Promoters are one type of gene regulators

  25. Transcription (recap) • The DNA is contained in the nucleus of the cell. • A stretch of it unwinds there, and its message (or sequence) is copied onto a molecule of mRNA. • The mRNA then exits from the cell nucleus. • Its destination is a molecular workbench in the cytoplasm, a structure called a ribosome.

  26. Translation • How do I interpret the information carried by mRNA to the Ribosome? • Think of the sequence as a sequence of “triplets”. • Think of AUGCCGGGAGUAUAG as AUG-CCG-GGA-GUA-UAG. • Each triplet (codon) maps to an amino acid.

  27. The Genetic Code • f : codon  amino acid • 1968 Nobel Prize in medicine – Nirenberg and Khorana • Important – The genetic code is universal! • It is also redundant / degenerate.

  28. The Genetic Code

  29. Proteins • Composed of a chain of amino acids. R | H2N--C--COOH | H 20 possible groups

  30. Proteins R R | | H2N--C--COOH H2N--C--COOH | | H H

  31. Dipeptide This is a peptide bond R O R | II | H2N--C--C--NH--C--COOH | | H H

  32. Protein structure • Linear sequence of amino acids folds to form a complex 3-D structure. • The structure of a protein is intimately connected to its function. The 3-D shape of proteins gives them their working ability – the ability to bind with other molecules.

  33. Our course (2427) Part 1, DNA: Assembly, Evolution, Alignment Part 2, Genes: Prediction, Regulation Part 3, Structures & Interactions transcription DNA rRNA snRNA translation POLYPEPTIDE mRNA

  34. Computer Scientists vs Biologists(courtesy Steven Skiena, SUNY Stony Brook)

  35. Computer scientists vs Biologists • Biologists strive to understand the very complicated, very messy natural world. • Computer scientists seek to build their own clean and organized virtual worlds.

  36. Computer scientists vs Biologists • Computer scientists get high-paid jobs after graduation. • Biologists typically have to complete one or more post-docs...

  37. Computer scientists vs Biologists • Nothing is ever completely true or false in Biology. • Everything is either true or false in computer science.