DNA, RNA and Protein Synthesis Sections 12-1 to 12-4

DNA & its structure

Chromosome Structure of Eukaryotes Nucleosome DNA double helix Coils Supercoils I. DNA is: into chromosomes Found in ____ Histones Nucleotides bundled nucleus

DNA = deoxyribonucleic acid Why is DNA important? code for PROTEINS, which determine your traits Monomer (building block) of DNA = NUCLEOTIDE

3 Parts of a Nucleotide: 1. Sugar (deoxyribose) 2. Phosphate 3. A nitrogen base (Adenine, Cytosine, Guanine & Thymine)

One Nucleotide

II. Structure of DNA double-stranded molecule double-helix (twisted) shape Sugars & phosphates = BACKBONE of DNA strands

2 nitrogen bases attach in center of DNA strands (HYDROGEN bond)

2 Groups of Nitrogen bases : 1) Purines Adenine & Guanine 2 chemical rings 2) Pyrimidines Cytosine & Thymine 1 chemical ring

III. Complementary Base Pairing Adenine bonds to Thymine (A-T) Cytosine bonds to Guanine (C-G)

Hydrogen bonds Deoxyribose Phosphate

DNA Model Activity Color each component a different color Cut out pieces Have a key for all pieces Circle one nucleotide QUES #1- How many nucleotides are there in your model? QUES #2- How is this model an inaccurate representation of DNA? (List at least 3 ways)

IV. History of DNA 1. Rosalind Franklin took x-rays of DNA crystals & determined its “spiral” helix shape never recognized for her work

Franklin’s x-ray of DNA Rosalind Franklin

1st to “discover” & publish shape/structure of DNA in 1953 2. James Watson & Francis Crick 1st to “discover” & publish shape/structure of DNA in 1953 used Franklin’s x-rays to determine its shape received Nobel Prize

James Watson & Francis Crick

V. DNA Replication how DNA copies itself Occurs in NUCLEUS Importance = ensures new cells (made in mitosis) have same info.

VI. DNA Replication Steps: Step 1: Separating the DNA Helicase enzyme split the base pairings into two strands

Step 2: Constructing complementary bases of DNA DNA polymerase enzymes construct new complementary bases & insert on the original DNA strand

There are many enzymes working at once so replication can occur quickly.

Step 3: Accuracy and Repair Enzymes proofread and repair incorrectly bonded bases. Any error is called a mutation

Mutations can have harmful effect Beneficial effect No effect (junk DNA)

RNA, Transcription & Translation PROTEIN SYNTHESIS

RNA = ribonucleic acid Why is RNA important? 1. Carries code from DNA (in nucleus) to make proteins (at ribosomes) 2. RNA acts like a messenger between DNA & proteins!

Differences between DNA & RNA DNA vs. RNA Double-stranded Single-stranded Double helix shape Coiled strand

DNA vs. RNA Sugar = DEOXYRIBOSE Sugar = RIBOSE A, C, G & T bases A, C, G & U bases U = uracil; pyrimidine that pairs with ADENINE

3 Types of RNA: 1. Messenger RNA (mRNA) – brings info. in DNA to ribosome 2. Transfer RNA (tRNA) –binds to mRNA on 1 end & has specific amino acid on other end.

3. Ribosomal RNA (rRNA) – makes up ribosomes where proteins are made * All 3 RNA’s work together to make proteins!

I. TRANSCRIPTION = makes mRNA from DNA Occurs in NUCLEUS A. Steps: 1) DNA unwinds & separates 2) RNA nucleotides PAIR w/ bases on 1 DNA strand only

3) When finished, new mRNA strand BREAKS AWAY & leaves nucleus; DNA strands REJOIN.

http://www. brooklyn. cuny. edu/bc/ahp/BioInfo/graphics/Transcription http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/graphics/Transcription.01.GIF

II. TRANSLATION = forms PROTEINS using mRNA (code copied from DNA) DNA-RNA-Protein Synthesis II. TRANSLATION = forms PROTEINS using mRNA (code copied from DNA) - Occurs at RIBOSOMES A. Steps: 1) mRNA goes to ribosome DNA-RNA-Protein Synthesis

2) tRNA’s temporarily pair w/ mRNA. a) ANTICODON (3 tRNA nucleotides ) pairs to CODON on mRNA b) On opp. end of tRNA, AMINO ACID (for mRNA codon) is attached

3) As tRNA’s attach, a.a. link/bond & each tRNA leaves 4) When STOP codon is reached, a.a. chain is complete. * Chain of amino acids = PROTEIN!

Protein = amino acids linked together Anticodon Codon tRNA mRNA Amino acid Protein = amino acids linked together Anticodon Codon http://library.thinkquest.org/C004535/media/translation.gif

III. Protein Synthesis (vocab) A. PROTEIN (polypeptide) = chain of AMINO ACIDS (linked by PEPTIDE BONDS). * Order of a.a. determines type of protein made

B. Amino acid determined by codon on mRNA CODON = 3 consecutive mRNA nucleotides that code for 1 amino acid.

IV. What is the amino acid for the following mRNA codons? CCC = Pro (short for proline) UGU = Cys (short for cysteine) AGU = Ser (short for serine)

Mutations = permanent change in DNA sequence May be harmful May have no effect May be beneficial

Two types of DNA mutations: 1. Point mutation = one base is substituted in DNA Only 1 codon/amino acid affected May or may not affect protein

2. Frameshift mutation = a base is added or deleted All codons change (shifted) Completely changes protein

U A A G G C A G U U U U A A C G G C A G U U U PRACTICE Original mRNA mutation mRNA What type of mutation? Were all the a.a. affected?

A T T C C G T C A A A T A A G G C A G T T T 1. Write the complementary strand to the DNA under the process of REPLICATION. A T T C C G T C A A A T A A G G C A G T T T

A T T C C G T C A A A U A A G G C A G U U U 2. Write the complementary strand to the DNA under the process of TRANSCRIPTION. A T T C C G T C A A A U A A G G C A G U U U