A Introduction Part 2

DNA Deoxyribonucleic Acid deoxy: no oxygen ribo: sugar nucleic: nucleotides • • • • • • • •

DNA and RNA are polymers: composed of repeating subunits, or monomers James Watson & Francis Crick found the structure of DNA Rosalind Franklin & Maurice Wilkins took the first x-ray Double-stranded Helical Tight-hand twist 10 base pairs = 1 full twist 3 parts: 1. sugar 2. phosphate 3. nitrogenous base

Nitrogenous Bases A=T C≡G Purine: double ring of carbon & nitrogen atoms; adenine & guanine

Pyrimidines: single ring of carbon & nitrogen atoms; thymine & cytosine

DNA Replication 1. - Helicase separates strands of DNA (breaks hydrogen bonds) - Forms a replication fork 2. - DNA polymerase adds complimentary nucleotides to original strands - Covalent bonds form between old and new nucleotides - hydrogen bonds form between old and new nucleotides

3. - DNA polymerase finishes and falls off, leaving 2 identical double-stranded DNA - semi-conservative replication (one old strand with one new strand) RNA Ribonucleic Acid • A copy of a segment of DNA used to make proteins • RNA produced in nucleolus DNA No oxygen Long Double stranded Uses thymine for nitrogenous base

RNA Has oxygen Short Single stranded Replaces thymine with uracil

Protein Structure • • • • • •

DNA and RNA are polymers: composed of repeating subunits, or monomers Made of chains of amino acids Amino acids joined together by mRNA, rRNA, and tRNA to form a polypeptide poly: many; peptide: protein 20 different amino acids Codon: a 3 nucleotide sequence in the mRNA

Types 1. mRNA o o 2. rRNA o o 3. tRNA o o

messenger RNA single stranded copy of a segment of DNA ribosomal RNA protein synthesis transfer RNA transfers amino acids to ribosomes to make proteins

Protein Synthesis 1. - RNA bonds to DNA promoter (start region) and unwinds DNA 2. - RNA polymerase adds free-floating nucleotides to make RNA DNA RNA

A T C G A C U A G C U G

3. - RNA polymerase reaches termination signal and releases RNA - DNA zipped - RNA leaves nucleus

Transcription • Process in which RNA is produced from DNA • All 3 types of RNA transcribed in the same manner RNA polymerase 1. binds to DNA molecule 2. causes separation of the complementary strands of DNA 3. directs the formation of hydrogen bonds between the bases of a DNA strand & complementary bases of RNA nucleotides (that are floating in the nucleus) 4. moves along the section of DNA, establishing the sugar-to-phosphate bonds between the RNA nucleotides (similar to DNA replication) 5. when it reaches the sequence of bases on the DNA that act as a termination signal, the enzyme triggers the release of the newly made RNA Translation 1. Initiation o mRNA floats towards the rRNA and binds together o tRNA finds start codon (AUG; Methionine) and brings the first amino acid o tRNA has anticodons, which are the complimentary base pairs to mRNA codons o each tRNA can carry or transfer one specific amino acid 2. Elongation o Second tRNA binds next to the first o Peptide bonds form between the amino acids o First tRNA leaves 3. Elongation Continued o rRNA moves down the mRNA o more tRNA’s bind on transferring more amino acids 4. Termination o rRNA reaches stop codon o no amino acid for stop codon 5. Disassembly o mRNA, tRNA, rRNA, polypeptides float away o polypeptide heads for Golgi o multiple rRNA’s can be on one mRNA at the same time to increase the production of proteins

Genetic Code: system that contains information needed by cells for proper functioning

Gene: region of DNA that directs the formation of a polypeptide