DNA, Genes, and Proteins

Characteristics are based on the same genetic code stored in DNA

DNA (Deoxyribonucleic Acid)

• holds the coded information for how to make every protein a living organism might need throughout its entire life.

Double Helix

Nucleotides

Parts of DNA

Nucleotides• The subunits of the DNA strand• 2 structural versions• Purine• Pyrimidine

Bases of DNASize and structure of the specific nucleotides cause• Adenine & Thymine to always pair together • Cytosine &Guanine always pair together.

Complementary strands held together by Hydrogen bonds

DNA 5’ and 3’ ends

• The carbons in the deoxyribose are numbered 1’5’

• Each strand in the double helix runs opposite of the other

DNA Replication• 2 steps– Unzipping DNA – Filling in space with free

floating nucleotides– 2 new Daughter strands• Half original and half new

• Replication happens in bubbles throughout the DNA• not from top to bottom

Replication: 1st step• Unwind DNA– Enzymes are needed to complete the process

Replication Bubblereplication fork

helicase

DNAPolymerase III

Replication: 2nd step Build daughter DNA strand

add new complementary bases

More enzymes needed to complete the process

energy

How it Happens

• DNA is a long string of bases (A, T, G, C)• Small sections of these bases that are

codes for a protein are called genes• 1 gene is a recipe for 1 protein

Proteins• chains of amino acids• The order of amino acids in the chain

determines the shape of the protein• The shape of the protein determines what its job

is

Hemoglobin(protein that caries oxygen in your blood)

StructureCollagenAlong with many other proteins it helps build muscles

Or you can just inject it directly into your face

Regulation

Insulin A protein that helps regulate blood sugar levels

Enzymes

H2O2 H2O + O2

Catalase is an enzyme that breaks down hydrogen peroxide in your body

Some enzymes can put stuff together like DNA Polymerase

Meet Andi…

What makes him glow??

Aequorea victoria

A protein called GFP or Green Fluorescent Protein

GFP DNA Coding Sequenceatgagtaaag gagaagaact tttcactgga gtggtcccag ttcttgttga attagatggc gatgttaatg ggcaaaaatt ctctgtcagt ggagagggtg aaggtgatgc aacatacgga  aaacttaccc ttaattttat ttgcactact gggaagctac ctgttccatg gccaacactt gtcactactt tctcttatgg tgttcaatgc ttctcaagat acccagatca tatgaaacag catgactttt tcaagagtgc catgcccgaa ggttatgtac aggaaagaac tatattttac aaagatgacg ggaactacaa gacacgtgct gaagtcaagt ttgaaggtga tacccttgtt aatagaatcg agttaaaagg tattgatttt aaagaagatg gaaacattct tggacacaaa atggaataca actataactc acataatgta tacatcatgg gagacaaacc aaagaatggc atcaaagtta acttcaaaat tagacacaac attaaagatg gaagcgttca attagcagac cattatcaac aaaatactcc aattggcgat ggccctgtcc ttttaccaga caaccattac ctgtccacac aatctgccct ttccaaagat cccaacgaaa agagagatca catgatcctt cttgagtttg taacagctgc taggattaca catggcatgg atgaactata caaa

Gene For Making GFP

• Reading or “expressing” Genes

Two major Steps• Transcription• Translation

Moving from Gene to protein

Transcription (Step 1)• Copying a short

segment of DNA (a gene)

• Helps moves genetic information from inside the nucleus out to the ribosomes using a special nucleic acid called RNA

DNA RNA

Deoxyribose

Double Stranded

Adenine - Thymine Adenine -

Transcription (Step 1)• Transfer information

from DNA onto a strand of RNA… specifically mRNA

Gene

Messenger RNA or mRNA• Allows the genetic

code to be read by ribosomes that are located in the rough ER

Translation• mRNA is read by

ribosomes and then translated into a protein Chain of amino Acids

• tRNA helps bring amino acids together to form protein chain

http://www.concord.org/~btinker/workbench_web/models/eukTranslation.swf

Cracking the Code

Starting and stopping the

protein sequence

Dead or Alive?

Viruses and DNA Replication

What constitutes being alive?

Virus structure

• Piece of DNA or RNA surrounded by a protein coat called a capsid

• Sometimes that capsid is surrounded by a lipid bi-layer – This is to help it enter

through the cell membrane

~Virus Replication~

• Virus injects its DNA into a host cell• Merges with host cell’s DNA• As Host cell replicates DNA replicates as well• Virus is Dormant

The lysogenic cycle

The Lytic cycle

• Virus injects DNA into a host cell• Host reads DNA and produces new viruses• Host cell fills up with viruses until it pops or lyses

Mutations

• Point mutations (substitutions)- may or may not be a big deal

• Frame shift mutations (insertions or deletions)- always a big deal

Gene MutationsWhat’s the difference? Point mutation

When a single base is switched

Example of a point mutation

• Sickle cell anemia

• One base change- one amino acid substitution

• Hemoglobin does not function normally

hemoglobinA protein in your blood that holds oxygen

Sickle cell anemia is a point mutation problem

Other point mutations

threonine glycine proline phenylalanine

mRNA ACU – GGA – CCA -- UUC

Change the last C to a U- what happens to the protein?

Turn this into a U

Frame-shift mutations

Deletion

Insertion

Which is worse?Point Mutation? Why? What does a point mutation do to the whole protein?

Frame-shift Mutation? Why? What does a frame-shift mutation do to the whole protein?