DNA Structure. DNA Molecular Structure 5/29/2012. Chapter 4 Genetics and Cellular Function

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1 5/29/202 hapter enetics and ellular Function D and R the nucleic acids D replication enes and their action D to Proteins (a) D Structure D threadlike molecule with uniform diameter, but varied length ow many in most human cells? Double helix omposed of ucleotides. phosphate group 2. deoxyribose sugar 3. nitrogenous base - (c) ydrogen bond -2 D Molecular Structure itrogenous Bases of D D and other nucleic acids are polymers (chains) of Each nucleotide consists of one sugar - deoxyribose one phosphate group one nitrogenous base P 2 denine 2 here are only four nitrogenous bases denine () uanine () ytosine () hymine () Purines 2 Pyrimidines denine () 2 2 uanine () 3 Phosphate Deoxyribose D bases - ytosine () hymine () Uracil (U) omplementary Base Pairing itrogenous bases united by D base pairing Law of omplementary Base Pairing one determines base sequence of other Depending on which chromosome 50 to 250 million base pairs iny piece of D ydrogen bond Mitosis? Mitosis: division of cells that results in daughter cells with the same the genetic information that the original cell had. 6 Diploid 2n 6 6 Diploid 2 n 27-6

2 5/29/202 D Replication and ell ycle D Replication before cell divides, it must must duplicate its D (replication) - so each new cell gets exact copy of D When does this occur during the cell cycle? 2. D Polymerase adds complimentary Don t forget Law of omplementary Base Pairing. elicase breaks bonds at replication fork 3. D ligase joins segments together -7 2 D each with ½ of original D = Semi-conservative replication 3-52 D Replication Key: = denine = hymine Incoming ontinuous = ytosine = uanine (e) Parental D Replication fork Key (a) D helicase Replication fork (c) D polymerase ap in replication Discontinuous (d) D ligase D polymerase ld (template) Leading ewly made ew forming Lagging uman natomy and Physiology, 7e by Elaine Marieb & Katja oehn D of one chromatid ld (template) D polymerase opyright 2007 Pearson Education, Inc., publishing as Benjamin ummings. Mutations in the ormal or Slide Sorter views. ll animations will appear after viewing D polymerase does make mistakes But: checks new base pairs and tends to fix mistakes result is only error per billion bases replicated mutations - changes in D structure due to replication errors or environmental factors (radiation, viruses, chemicals) some mutations = no problem/some kill the cell, turn it cancerous or cause genetic defects in future generations -2 2

3 5/29/202 D Function D Function ene segment of D that codes for a specific protein humans have ~ 35,000 2% of total D other 98% is non-coding D plays role in chromosome structure regulation of gene activity (on-off sites) no function at all junk D Make Proteins!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ene segment of D that codes for a specific protein humans have ~ 35,000 2% of total D other 98% is non-coding D plays role in chromosome structure regulation of gene activity no function at all junk D -3 - enetic ode Millions of different proteins, all made from 20 amino acids, encoded by genes made of (,,,) enetic code rrangement of that code for amino acid sequence of proteins i.e., arrangement determines amino acid arrangement eneral: a D triplet a sequence of 3 D will code for amino acid codon - the 3 base sequence in mr -5 R: Structure and Function R Much smaller than D - a single nucleotide chain - Ribose sugar (not deoxyribose) - o thymine nitrogenous base (replaced by Uracil) 3 types of R. messenger R (mr) over 0,000 bases 2. R (rr) transfer R (tr) bases Function interprets code in D uses those instructions for protein synthesis -6 verview of Protein Synthesis all body cells contain identical genes (except sex cells and some immune cells) From D to Protein uclear envelope different genes are activated in different cells nce activated a gene:. Makes messenger R (mr) a mirror-image copy of the gene is made migrates from the nucleus to cytoplasm its code is read by the ribosomes 2. mr attaches to ribosomes ( R (rr) and enzymes) 3. transfer R (tr) delivers amino acids to the ribosome. ribosomes assemble amino acids in the order directed by codons of mr ranscription ranslation mr D Ribosome Polypeptide -7 Figure

4 5/29/202 ranscription: R Polymerase in the ormal or Slide Sorter views. ll animations will appear after viewing he enzyme that oversees mr synthesis Starts at a promoter site Breaks bonds & unwinds D dds complementary on D template following Law of omplimentary Base Pairing Joins R together to match D coding Reads a termination signal to stop transcription oding Promoter ermination signal emplate Unwound D ranscription unit R IR polymerase binds to polymerase promoter and unwinds 6 8 base pairs of the D template R polymerase bound to promoter R mr synthesis begins mr R R polymerase moves down D; mr elongates R polymerase mr synthesis is terminated D (a) mr transcript oding R polymerase Unwinding Rewinding of D of D in the ormal or Slide Sorter views. ll animations will appear after viewing emplate mr R-D hybrid region R Figure From D to Protein uclear envelope uclear membrane uclear pore mr R polymerase ucleus emplate of D ranscription D Released mr R Processing Pre-mR mr ranslation Ribosome Polypeptide Figure 3.33

5 5/29/202 ucleus ucleus uclear membrane R polymerase uclear membrane R polymerase uclear pore uclear pore mr mr Polysome: mr binding to ribosome Released mr emplate of D Released mr emplate of D mino acids fter mr processing, mr Small fter mr processing, mr Small tr minoacyl-tr odon 5 odon 6 odon 7 odon 5 odon 6 odon 7 Portion of mr Portion of mr Energized by P, each species of tr by aminoacyl-tr ucleus ucleus uclear membrane R polymerase uclear membrane R polymerase uclear pore uclear pore mr mr emplate of D mino acids emplate of D mino acids Released mr Released mr fter mr processing, mr Small tr minoacyl-tr fter mr processing, mr Small tr minoacyl-tr odon 5 odon 6 odon 7 odon 5 odon 6 odon 7 Portion of mr tr head bearing anticodon Portion of mr tr head bearing anticodon 2 Incoming aminoacyltr via its anticodon to complementary mr sequence (codon) at the site on the ribosome. Energized by P, each species of tr by aminoacyl-tr 3 s the ribosome moves along the mr, a new amino acid is added to the growing protein chain and the tr in the site is translocated to the P site. 2 Incoming aminoacyltr via its anticodon to complementary mr sequence (codon) at the site on the ribosome. Energized by P, each species of tr by aminoacyl-tr ucleus ranslation of mr uclear membrane uclear pore R polymerase ytosol Portion of mr mr nce its amino acid is released, tr is ratcheted to the E site and then released to reenter the cytoplasmic pool, ready to be recharged with a new amino acid. fter mr processing, mr Small odon 5 odon 6 odon 7 3 Released mr s the ribosome moves along the mr, a new amino acid is added to the growing protein chain and the tr in the site is translocated to the P site. emplate of D tr head bearing anticodon 2 Incoming aminoacyltr via its anticodon to complementary mr sequence (codon) at the site on the ribosome. mino acids tr minoacyl-tr Energized by P, each species of tr by aminoacyl-tr 8 Ribosomal s rejoin to repeat the process with the same D ucleus or another mr. 7 fter translating the entire mr, the 5 he preceding tr hands off ribosome dissociates the growing protein to the new into its two s. mr tr, and the ribosome links the new amino acid to the protein. tr anticodon binds Protein to complementary mr leaves mr codon. the nucleus. 2 Ribosome binds mr. U U U 3 tr binds an amino acid; binding consumes P. 6 tr is released from P DP + P i the ribosome and is available to pick up a new amino acid and repeat the process. Free tr tr Free amino acids -30 5

6 5/29/202 in the ormal or Slide Sorter views. ll animations will appear after viewing in the ormal or Slide Sorter views. ll animations will appear after viewing 3 Information ransfer from D to R Protein Synthesis emplate Figure Review of Peptide Formation D double helix 2 triplets on the template of D enetic ode: R codons code for amino acids according to a genetic code Remember there are 20 amino acids 3 orresponding codons of mr transcribed from the D triplets he anticodons of tr that bind to the mr codons 5 he amino acids carried by those six tr molecules 6 he amino acids linked into a peptide chain -35 Figure

7 5/29/202 Protein Packaging and Secretion Mechanism of ene ctivation Prolactin Prolactin receptors 7 asein Exocytosis ucleus Protein formed by ribosomes on rough ER. 2 Protein packaged into transport vesicle, which buds from ER. 3 ransport vesicles fuse into clusters that unload protein into olgi complex. olgi complex modifies protein structure. 2 P D P + P i 6 Secretory vesicles olgi complex Ribosomes 5 olgi vesicle containing finished protein is formed. 6 Secretory vesicles release protein by exocytosis. Regulatory protein (transcription activator) Rough Endoplasmic reticulum lathrin-coated transport vesicle Rough ER olgi complex 3 5 Lysosome mr for casein asein gene R polymerase Figure