Molecular Biology Chapter 9 DNA Deoxyribonucleic Acid DNA

Molecular Biology Chapter 9

DNA – Deoxyribonucleic Acid DNA stores genetic information copied and passed from generation to generation Directs the copying of itself DNA Replication Involved in protein production Transcription Translation

History of DNA – Watson & Crick Wanted to know if the genetic material was protein or DNA. 1953 Deduce exact structure of DNA Nucleic Acid Double Helix Made of nucleotides James Watson (left) and Francis Crick

Rosalind Franklin X-ray images of DNA

DNA Structure Double Helix is composed of a Backbone composed of alternating Sugar Phosphate Rungs Bases 5 -C sugar = Deoxyribose Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Nucleotide = Phosphate + Sugar + Base © 2013 Pearson Education, Inc.

FIGURE 9. 3 (a) Each DNA nucleotide is made up of a sugar, a phosphate group, and a base. (b) Cytosine and thymine are pyrimidines. Guanine and adenine are purines.

Phosphate group Nitrogenous base Sugar DNA nucleotide DNA double helix Nitrogenous base (can be A, G, C, or T) Thymine (T) Phosphate group Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone

Hydrogen bond (b) Atomic model

DNA Replication – semiconservative replication

Parental (old) DNA molecule Daughter (new) strand Parental (old) strand Daughter DNA molecules (double helices)

RNA - Ribonucleic Acid Structure of RNA: Sugar is Ribose No T, Uracil (U) instead Single stranded (ss)

Figure 10. UN 03 b Nitrogenous base Sugar Number of strands DNA RNA C G A T C G A U Deoxy. Ribose ribose 2 1

How do DNA and RNA work together? DNA makes a copy of itself in the form of RNA transcription RNA is used to make proteins Translation * Please note DNA replication is a completely separate process that is NOT related to transcription and/or translation!

Figure 10. UN 05 TRANSCRIPTION TRANSLATION Gene m. RNA DNA Polypeptide

Types of RNA 1. Messenger RNA (m. RNA) Carries the message from DNA directions for making a protein

Types of RNA con’t. 2. Transfer RNA (t. RNA) Carries and transfers amino acids to m. RNA

Types of RNA con’t. 3. Ribosomal RNA (r. RNA) Mixed with protein to make ribosomes Two subunits (large & small) used to facilitate translation

Figure 9. 19 The protein synthesis machinery includes the large and small subunits of the ribosome, m. RNA, and t. RNA. (credit: modification of work by NIGMS, NIH)

Figure 10. UN 06 Growing polypeptide Amino acid Large ribosomal subunit t. RNA m. RNA Anticodon Codons Small ribosomal subunit

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