1. BioEd Online The Molecular Basis of Heredity: Structures and Functions of Nucleic Acids by Raye L. Alford, PhD Baylor College of Medicine DNA Model by J. Watson and F. Crick © Cold Spring Harbor Laboratory Archives

2. www.BioEdOnline.org BioEd Online The Atomic Components of DNA and RNA Carbon (C) Hydrogen (H) Nitrogen (N) Oxygen (O) Phosphorus (P) Thomas Jefferson National Accelerator Facility, Office of Science Education The Periodic Table of Elements

3. www.BioEdOnline.org BioEd Online The Molecular Components of DNA and RNA (I) Bases DNA and RNA Adenine (A) Cytosine (C) Guanine (G) DNA Only Thymine (T) RNA Only Uracil (U) 2005 VisiScience Corporation. All Rights Reserved. Uracil Thymine Guanine Adenine Cytosine

4. www.BioEdOnline.org BioEd Online The Molecular Components of DNA and RNA (II) The Sugar – Phosphate Backbone DNA – Deoxyribose (Pentose) Sugar RNA – Ribose (Pentose) Sugar Phosphate Group Base + Sugar + Phosphate = Nucleotide Deoxyribose + Triphosphate Group Ribose + Triphosphate Group BASE 1 2 3 5 1 2 3 5 2005 VisiScience Corporation All Rights Reserved

5. www.BioEdOnline.org BioEd Online The DNA and RNA Strand Nucleotide + Nucleotide (n) = DNA (or RNA) strand Deoxyribonucleotides = DNA Ribonucleotides = RNA 2005 VisiScience Corporation. All Rights Reserved. 3' 5' Base 1'1' 3'3' 5'5'

6. www.BioEdOnline.org BioEd Online 5' 3' DNA is Double-Stranded Hydrogen bonds enable the DNA ladder. A always pairs with T. C always pairs with G. The sequence of one strand predicts the sequence of the other. 2005 VisiScience Corporation. All Rights Reserved. 3 4 5 2 1 4 5 1 6 3 2 8 7 9 6 Thymidine Two Hydrogen Bonds Adenosine 9 3 4 5 2 4 5 1 6 3 2 7 6 1 8 Cytidine Guanosine Three Hydrogen Bonds

7. www.BioEdOnline.org BioEd Online The DNA Double Helix The DNA ladder spirals in a double helix. There are 10 base pairs per turn. Each turn is 34 Angstroms high. The helix is 24 Angstroms wide. The major groove is the wider of the two grooves. The other groove is called the minor groove Redrawn from National Institute of Medical Sciences, NIH Major groove Minor groove Major groove Minor groove

8. www.BioEdOnline.org BioEd Online DNA Replication Replication relies on complementary base pairing. Replication occurs before Mitosis and Meiosis I. DNA replication is semi-conservative. DNA is synthesized by DNA polymerase. DNA is synthesized in a 5 to 3 direction. 5 5' 3' 5' Redrawn from National Center for Biotechnology Information 3' 5'3' 5'

9. www.BioEdOnline.org BioEd Online Transcription Like replication, transcription relies on base pairing. Instead of DNA, RNA is made. RNA is synthesized by RNA polymerase II. 3' 5' Nascent RNA Template Strand 5' 3' Coding Strand Elongation Site RNA Polymerase Unwinding Rewinding Movement of polymerase 2005 VisiScience Corporation. All Rights Reserved

10. www.BioEdOnline.org BioEd Online RNA Processing in Eukaryotic Cells Splicing out of introns, capping with 5' methyl cap, polyadenylation Exon 5' 3' Intron RNA IntronExon mRNA AAAAAAAn 2005 VisiScience Corporation. All Rights Reserved.

11. www.BioEdOnline.org BioEd Online Translation Ribosomes make proteins from the messages encoded in mRNA. Three nucleotide groups called codons encode one amino acid. This is the genetic code. Adapted from: L. Stryer. Biochemistry, 3rd ed.. 5' 3' Nearly completed protein Ribosome Beginning of protein mRNA

12. www.BioEdOnline.org BioEd Online The Genetic Code Each 3-nucleotide mRNA codon specifies a particular amino acid. Each tRNA transfers a particular amino acid. To use the chart, read from the mRNA. National Center for Biotechnology Information, National Library of Medicine, NIH MET- tRNA codon mRNA anticodon loop

13. www.BioEdOnline.org BioEd Online Summary of DNA DNA: is a complex macromolecule made of several basic atomic components. encodes genes, the instructions needed to make RNA and proteins. is a double helix. The complementary nature of the DNA helix permits its replication and transcription. is transcribed into RNA. 2005 VisiScience Corporation. All Rights Reserved.

14. www.BioEdOnline.org BioEd Online Summary of RNA mRNA (messenger RNA) is the template for the production of proteins, the molecules that build and comprise structures and perform enzymatic reactions. tRNA (transfer RNA) enables the transfer of amino acids into a growing polypeptide chain. rRNA (ribosomal RNA) is a component of protein- producing ribosomes.