From Genes to Proteins

1. From Genes to Proteins Biology 2121 Chapter 3

2. Nucleic Acids Nucleicacids: • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA) Monomers: ‘Nucleotide’ • 5-carbon sugar (ribose or deoxyribose) • Phosphate group • Nitrogen base (cytosine, guanine, thymine, cytosine)

3. DNA Phosphorus • Sugar-Phosphate backbone Nitrogen base pairs with the complementary base Double Helix Basepairingrules: • G pairs with C • T with A

4. RNA Samestructureexcept: • 5-carbon sugar is ribose • Uracil replaces thymine • Singlestranded, not double stranded Types • mRNA (messenger) • rRNA (ribosomal) • tRNA (transfer)

5. DNA and Genes Segments of DNA contain genes Genes • information to code for the production of polypeptides • on the surface of the ribosome.

6. DNA Replication Before a proteins can be built: • DNA must undergo replication • Helicase separates the strands of DNA • DNApolymerase assembles the nucleotides Occurs during Interphase • S-Phase Replicate this strand of DNA • AAGCCGTTA • Animation

7. Transcription Information from DNA must be transported to the ribosomes DNAunwinds and is copied by RNA • mRNA mRNA moves out of the nucleus (pores) and attaches to the ribosomes Transcribe this stretch of DNA • AAA TGC • Animation • Animation II

8. mRNA Editing Pre-mRNA will lose non-coding sequences called introns • ‘junk DNA’ Information codes for polypeptide (protein) • Exon

9. Translation Aminoacids • assembled on the surface of a ribosome Aminoacids • tRNA binds an amino acid • In cytoplasm tRNA bonds with sequences in the mRNA • codons • anticodon on tRNA bonds with codon on mRNA

11. Translation The codon sequences of mRNA may be translated into amino acids using the genetic code Always read from the mRNA! Translate: • AUG CAC GUU GGU • Animation

13. Polyribosomes A single stand of mRNA can produce hundreds of the same polypeptide in a short period of time.