Molecular Biology

I. History of DNA T.H. Morgan showed that differences in chromosomes determined fly traits What are chromosomes made of??? DNA and Protein.

Many other experiments showed DNA, not the protein, contains info. The DNA in one cell has ALL the info needed to make you!

Watson and Crick discovered that DNA looks like a spiral staircase and called it a Double Helix X-ray diffraction 3D model Lots and lots of math

Review: What is a polymer? Monomer?

Review: Molecules make chains (polymers) too One nucleotide = monomer Many nucleotides = DNA = polymer

Review: Which molecules make chains? DNA – chain of nucleotides RNA – chain of nucleotides Protein – chain of Amino acids

II. What is DNA Shape: Double Helix - - made of two chains of nucleotides; referred to as “strands” - chains are twisted together in a spiral

II. What is DNA Structure: DNA Nucleotides are made up of: A Nitrogen base – A, T, G or C A sugar - deoxyribose A phosphate Nucleotide

II. What is DNA Structure: The order of the bases in the chain is called the sequence. AGTC How many nucleotides? How many chains?

II. What is DNA Everyone has a unique sequence! AGTC

II. What is DNA Structure: Once a chain is built is it used as a template to build a second chain A G T C A G T C

II. What is DNA Structure: MUST FOLLOW CERTAIN RULES! A G T C A G T C

II. What is DNA Structure: Bases that pair up are called complementary A G T C A G T C

II. What is DNA Structure: Strong covalent bonds hold nucleotides together. A G T C A G T C

II. What is DNA Structure: Weak hydrogen bonds hold the chains together A G T C A G T C

III. Replication Making an exact copy of ALL of the DNA Every time a cell divides to make more cells, it must copy its DNA

III. Replication Before replication…. Think of DNA as a Closed zipper. A G T C A G T C Hydrogen bonds Covalent bonds

III. Replication Step 1: “Unzip the Zipper” Helicase breaks Hydrogen Bonds between chains - Opens the zipper A G T C A G T C

III. Replication Step 2: Each chain of nucleotides is used to build a two new chains using the enzyme DNA polymerase A G T C A G T C A G T C A G T C

III. Replication Step 2: Still must follow complementary base pair rules A binds with T G binds with C A G T C A G T C A G U C A G T C

III. Replication There are many links to Replication animations on our unit resource page!! Use these to help you understand!

III. Replication What are we left with? - 1 cell with twice as much DNA as usual - Now the cell can split into two and both have all necessary DNA

DNA is used to make RNA, too So first a little about RNA….

IV. Structure of RNA RNA is a nucleic acid RNA is made of nucleotides Single strand (chain) of nucleotides A G U C

The sugar in RNA’s nucleotide is Ribose Bases are A, G, C and Uracil RNA contains information RNA contains 1 recipe A G U C IV. Structure of RNA

RNA is temporary and unstable A G U C IV. Structure of RNA

IV. Types of RNA mRNA – messenger RNA; –Contains the info to assemble proteins rRNA – Ribosomal RNA –Make up part of the ribosome, where proteins are made tRNA – transfer RNA - brings Amino Acids to ribosome

Uses DNA to make a chain of RNA – Only copies one recipe at a time. Each recipe is called a gene! V. Transcription

Step 1: Open DNA zipper –Just like replication we first need to separate the DNA strands V. Transcription A G T C A G T C

Step 2: Make the RNA –Using same pairing rules copy one chain of DNA into RNA –A’s in the DNA will pair with U’s in the RNA!! V. Transcription

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

Step 3: Chains of DNA pair up again, RNA gets kicked out V. Transcription A G U C A G T C A G T C Now we have a temporary copy of one of our recipes!

–Replication and Transcription need DNA so where do they take place? - Where do we Make protein? V. Transcription

–So if we need the mRNA to make protein, what has to happen after we transcribe it? V. Transcription

- Sections of DNA that contain the recipe for a single protein. A gene is only active if it gets transcribed into RNA. Genes that are not transcribed do not give you any traits. VI. Genes

After transcription we have: The directions to make the protein The factory to build the protein The building blocks to make protein All we need is to translate the information from “nucleotide” to “amino acid”

VII. Genetic Code: Think of the genetic code as a “Nucleotide to Amino acid” dictionary A U G G A G C Codon 1Codon 2

VII. Genetic Code: Every three bases of the mRNA is called a Codon A U G G A G C Codon 1Codon 2

VII. Genetic Code: Each Codon translates to a different Amino Acid. - cell reads codons to make protein A U G G A G C Codon 1Codon 2

VII. Genetic Code: AUG is always the first codon – means “Start here!” GGC means “now go get glycine” UAG means “Stop! You’re done!” A U G G A G C Codon 1Codon 2

VII. Genetic Code: There are 20 different amino acids and 64 codons. So… Some codons “mean” the same amino acids (GGC and GGG) A U G G A G C Codon 1Codon 2

VII. Genetic Code: For each codon there is a tRNA with a complementary Anticodon

VIII. Translation: Cell reads codons to make a particular chain (sequence) of amino acids - a chain of amino acids is a PROTEIN

VIII. Translation: Watch the animations and tell me what is happening

VIII. Translation: Step 1: mRNA lines up to be read by ribosome A U G G A G C C A G G U U A

VIII. Translation: Step 2: tRNA’s with anticodons that are complementary to codons line up A U G G A G C C A G G U U A UAC AA1 CUC AA2

VIII. Translation: Step 3: Amino Acid 1 is linked to amino acid 2 with a peptide bond A U G G A G C C A G G U U A UAC AA1 CUG AA2

VIII. Translation: Step 4: empty tRNA leaves and Ribosome shifts to a new codon A U G G A G C C A G G U U A U A C AA1 CUG AA2 GGU AA3

VIII. Translation: Step 5: steps repeat until stop codon is reached A U G G A G C C A G G U U A AA1 CUC AA2 GGU AA3 CCA AA4

VIII. Translation: Step 5: steps repeat until stop is reached U G G A G C C A G G U U A AA1 AA2 G G U AA3 CCA AA4 G A U C STOP

VIII. Translation: Step 6: protein is released U G G A G C C A G G U U A CCA AA1 AA2AA3 AA4 G AUC STOP