{ DNA Deoxyribonucleic Acid

History What is passed on from parents to offspring? Protein or DNA? DNA! What is the structure, what does it look like?

DNA Structure 1.Chargaff 1.Watson, Crick, Franklin and Wilkins

Chargaff Rule

Franklin and Wilkins

Model of DNA Structure

Hydrogen Bonds Complementary base pairing

Nucleotide

Backbone Rungs

Replication Enzyme that unzips Helicase SSBP’s Single Stranded Binding Proteins Replication Video

DNA had a 5’ and 3’ side Antiparallel

Only add to 3’ side of the DNA molecule 5’ and 3’ ends

Enzyme adds Nucleotide to the 3’ end

How does so much DNA get copied? - Replication Bubbles - Replication fork

Primer Short sequence of RNA that is needed to begin DNA synthesis

DNA Polymerases DNA Polymerase III Only works by adding nucleotides to the 3’ end of the NEW strand Works in 5’  3’ direction DNA Polymerase I Removes RNA from Primer and adds DNA

Ligase- attaches Okazaki fragments of the lagging strand “Like Glue”

DO NOW

  16/student_view0/chapter14/animations.html# 16/student_view0/chapter14/animations.html# McGraw Hill Website

Central Dogma DNA  RNA  Protein

Transcription

DO NOW 1. 3 ways DNA is different from RNA

Transcription 3 Steps 1.Initiation 2.Elongation 3.Termination

Initiation Promoter Region- beginning of a gene TATA Box - part of the promoter, upstream of the gene -sequence of T’s and A’s RNA Polymerase unwinds the DNA

Elongation -RNA Polymerase – Only adds to the 3’ end of RNA -Antiparallel -Base pairing rules -U or Uracil instead of T -mRNA- messenger RNA

Termination Terminator Sequence- sequence of T’s in the DNA Terminator Sequence- sequence of T’s in the DNA Primary RNA transcript is released (pre-mRNA) Primary RNA transcript is released (pre-mRNA)

RNA Processing Primary RNA transcript( pre- mRNA), modified before it leaves the nucleus 5’ end G Cap- modified Guanine, tell its to go to the Ribosome 3’ end Poly A tail – inhibit degradation

RNA Processing Introns- parts of DNA that are not expressed between exons Exons - genes are expressed mRNA splicing- remove the intros - exons  exit as mature RNA transcript - expressed Splisosome- cuts the RNA and joins the exons

Translation 3 nucleotides in the mRNA is called a codon.

20 amino acids Genetic Code- information encoded in genetic material translated into amino acid sequences 4 x 4 x 4= 64 One start and 3 stop signals

Universal

shape

Average Protein is 400 aa avg RNA ( exons) 1200

Translation- mRNA to protein tRNA ( transfer RNA)- transfer amino acids to a growing polypeptide Anticodon- complementary to the mRNA codon

3 steps of Translation 1.Initiation 2.Elongation 3.Termination

- Bring together mRNA, tRNA, - ribosome ( small subunit) - Binds the 5’ cap - Start codon AUG – Met, Methionine - Then the large subunit - Antibiotics Translation- Initiation

 E site, P site, A site  First one tRNA P site, A site afterwards Translation- Elongation

Termination Translation ends when one of three stop codons, UAA, UAG, or UGA, enters the A site Ribosomes separate, polypeptide released

Mutations

Sickle Cell Anemia

438-base sequence.

Can’t Carry Oxygen

Tay Sachs  Inherited genetic mutation  Gene codes for an enzyme that breaks down fatty acids  Build up of fatty acids in the brain

Mutation  Change in the nucleotide Sequence ( letters/bases) of a gene 1. Base Substitution ( can be bad or silent) 2. Base Addition/ Deletion- worse - alter group of 3 Affects the PROTEIN

Mutagens cause Mutations  Errors in DNA replication  Xray, UV light  Sometimes GOOD? How so?