DNA, RNA, & Protein Synthesis Unit4 – Lecture3

DNA DNA = De-oxy-ribo-nucleic Acid “blueprint” for traits double helix shape composition: polymer of nucleotide monomers nucleotide [3 parts]: sugar [deoxyribose] phosphate nitrogen base

Nitrogen Bases Nitrogen Bases: are complementary: adenine [A] bonds with thymine [T] cytosine [C] bonds with guanine [G]

Nitrogen Bases – cont’d amount of A = amount of T amount of C = amount of G purines: A & G pyrimidines: C & T

Discuss With what you just learned, find the answer to the following math problem: If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain?

76 / 2 = amount of C or amount of G Discuss If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain? if A = 12% then T = 12% total = 24% A&T 100% - 24% = amount of C&G 76% = amount of C&G 76 / 2 = amount of C or amount of G C = 38%, G = 38%

DNA – cont’d Watson & Crick [1953] proposed the structure of DNA stole the work of Rosalind Franklin X-Ray Crystallography

DNA Replication happens in the cell nucleus occurs during interphase

DNA Replication – cont’d enzyme unzips DNA double strand by breaking the hydrogen bonds between bases free-floating bases bond to open DNA

DNA Replication – cont’d continues… end result = 2 strands, ½ new & ½ old DNA repeat.

RNA RNA – Ribo-nucleic Acid sugar = ribose [instead of deoxyribose] single stranded has nitrogen base Uracil instead of Thymine A bonds with U C bonds with G

Discuss Restate to your partner what the three differences are between RNA and DNA.

RNA – cont’d [RNA] three types: mRNA – messenger complementary to DNA ferries DNA’s message out of the nucleus contains codons codon – segment of three bases in mRNA 1 codon = 1 amino acid or “start” or “stop” 20-some of them exist

Codon Chart

RNA – cont’d [RNA] [three types:] tRNA – transfer ferries amino acids to ribosome contains “anticodons” complementary to mRNA rRNA – ribosomal makes up the ribosomes

RNA – cont’d [RNA] [three types:] rRNA – ribosomal makes up the ribosomes

Name and explain the three types of rna to your partner. Discuss Name and explain the three types of rna to your partner.

Protein Synthesis transCription DNA  mRNA occurs in the nucleus process begins at “promoter” promoter tells where to start copying DNA sequence

Protein Synthesis transCription enzyme unzips DNA but RNA bases pair instead of DNA bases complementary bases are added

Protein Synthesis transCription continue adding bases until a “termination sequence” is located. mRNA carries message outside of the nucleus through nuclear pores into the cytoplasm

Protein Synthesis transLation mRNA  protein ribosomes read mRNA and use tRNA to make proteins steps:

Protein Synthesis transLation ribosomes clamp onto mRNA strand finds “start” codon [AUG] tRNA molecule containing matching anti-codon moves to ribosome tRNA enters ribosome; attaches to strand

Protein Synthesis transLation another tRNA enters ribosome ribosome bonds amino acids [peptide bond] first tRNA leaves, another enters repeat until “stop” codon is reached

Write this down! Any nitrogen bases that are BEFORE the “start” or AFTER the “stop” are NOT translated into amino acids.

Protein Synthesis transLation result – chain of amino acids linked by peptide bonds = polypeptide = protein polypeptide processed and shipped using ER & Golgi.

Let’s Try It C C A T A C G G T G T C T C C G A T A T T T T A is this DNA or RNA? how do you know? transcribe the DNA into mRNA C C A T A C G G T G T C T C C G A T A T T T T A G G U A U G C C A C A G A G G C U A U A A A A U find the start codon [AUG]

Let’s Try It G G U A U G C C A C A G A G G C U A U A A A A U beginning with AUG, separate your mRNA into codons. A U G / C C A / C A G / A G G / C U A / U A A / A A U beginning with your AUG, translate your mRNA into amino acids keep translating until “stop” codon is reached

Codon Chart

Let’s Try It A U G / C C A / C A G / A G G / C U A / U A A / A A U MET / PRO / GLN / ARG / LEU / (stop) 