BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 10 Molecular Biology of the Gene Modules 10.1 – 10.5

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA is a nucleic acid, made of long chains of nucleotides DNA and RNA are polymers of nucleotides Figure 10.2A Nucleotide Phosphate group Nitrogenous base Sugar PolynucleotideSugar-phosphate backbone DNA nucleotide Phosphate group Nitrogenous base (A, G, C, or T) Thymine (T) Sugar (deoxyribose)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA has four kinds of bases, A, T, C, and G Figure 10.2B Pyrimidines Thymine (T)Cytosine (C) Purines Adenine (A)Guanine (G)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA is also a nucleic acid –RNA has a slightly different sugar –RNA has U instead of T Figure 10.2C, D Phosphate group Nitrogenous base (A, G, C, or U) Uracil (U) Sugar (ribose)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The structure of DNA consists of two polynucleotide strands wrapped around each other in a double helix Figure 10.3C Twist 1 chocolate coat, Blind (PRA)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hydrogen bonds between bases hold the strands together –Each base pairs with a complementary partner –A pairs with T –G pairs with C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Three representations of DNA Figure 10.3D Ribbon modelPartial chemical structureComputer model Hydrogen bond

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In DNA replication, the strands separate –Enzymes use each strand as a template to assemble the new strands DNA REPLICATION DNA replication depends on specific base pairing Parental molecule of DNA Figure 10.4A Both parental strands serve as templates Two identical daughter molecules of DNA Nucleotides A A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Untwisting and replication of DNA Semi-conservative model of replication Figure 10.4B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA replication begins at specific sites DNA replication: A closer look Figure 10.5A Parental strand Origin of replication Bubble Two daughter DNA molecules Daughter strand

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each strand of the double helix is oriented in the opposite direction DNA is “read” from 3’ end to 5’ end Figure 10.5B 5 end3 end 5 end P P P P P P P P

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings How DNA daughter strands are synthesized Template strand read from 3’ to 5’; Daughter strand build from 5’ to 3’ 5 end P P Parental DNA Figure 10.5C DNA polymerase molecule Daughter strand synthesized continuously Daughter strand synthesized in pieces DNA ligase Overall direction of replication 5 3 The daughter strands are identical to the parent molecule

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Leading vs. Lagging Strands

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA Synthesis 1.Helicase unwinds double helix 2.Single stranded binding proteins stabilize unwound DNA 3.Priming of DNA synthesis with primase 4.DNA polymerase elongates new strands in the 5’  3’ direction 5.DNA ligase catalyzes linkage of Okazaki fragments

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Summary of DNA Replication

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Somatic cells of each species contain a specific number of chromosomes –Human cells have 46, making up 23 pairs of homologous chromosomes Chromosomes are matched in homologous pairs Chromosomes Centromere Sister chromatids Figure 8.12

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Human Diploid Somatic Cell (46 chromosomes)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Human Haploid Gamete Cell (23 chromosomes)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings What do Chromosomes do? DNA’s job is to carry the instructions for making proteins DNA  transcription  RNA  translation  Protein Central Dogma of Molecular Biology DNA RNA Polypeptide TRANSCRIPTION TRANSLATION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Codon

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA ReplicationRNA Transcription Two new molecules of double-stranded DNA are produced One new molecule of single-stranded RNA is produced Adenine on one DNA strand binds to Thymine on the second DNA strand Adenine on DNA binds to Uracil on RNA The entire chromosome is replicated Only a small portion of the DNA molecule is transcribed to RNA, varies based on cell’s needs at the time