DNA Chapter 10

The Code of Life

HistoryGriffithHershey and ChaseChargaffLinus Pauling Maurice WilkinsRosalind FranklinFrancis CrickJames Watson

ModelDouble HelixBuilding Blocks-NucleotidesSugar-DeoxyribosePhosphateNitrogen Base

Types of Nitrogen Bases

Pyrimidines and Purines

•DNA has four kinds of bases, A, T, C, and G

thymine cytosine adenine guanine

pyrm

Hydrogen bonds between bases hold the strands together

Each base pairs with a complementary partner

A pairs with TG pairs with C

DNA stands for_____________.Describe the structure and replication of DNA.Describe Transcription.Describe Translation.

DNA is made up of building blocks called nucleotides. A nucleotide consists of a phosphate, a sugar (deoxyribose) and a nitrogen base.

There are two kinds of bases-purines(adenine and guanine) and pyrimidines(cytosine and thymine). Purines have a double ringed structure and pyrimidines have a single ringed structure.

A pairs with T and they join with a double hydrogen bond and C pairs with G and they join with a triple bond. DNA is anti-parallel. Its structure is called a double helix.

In DNA replication, the strands separate.Enzymes use each strand as a template to assemble the new strands

DNA replication begins at specific sites

Each strand of the double helix is oriented in the opposite direction

DNA Replication

Where? NucleusWhen? before cell division so that each cell can have a complete set of instructionsWhat? DNA, free nucleotides, enzymes and energyEnzymes (helicases) unwind the DNA. Then it unzips beginning in the middle-points of origin.Free DNA nucleotides come in and join with complimentary base on each strand.

Enzymes join the sides of the new DNA strands.Each strand is half old and half new. Thus this process is semi-conservative.

RNA vs DNARibose-deoxyriboseRNA is single stranded and DNA is double strandedUracil instead of thymine

A specific gene specifies a polypeptide

The “words” of the DNA “language” are triplets of bases called codons.The codons in a gene specify the amino acid sequence of a polypeptide.

Virtually all organisms share the same genetic code

Transcription

Where? NucleusWhy? DNA wants to send out a message.What? DNA, free RNA nucleotides, enzymes and energyFirst, a section (gene) of DNA unzips.Then RNA nucleotides come in and join with the template side of the DNA.Enzymes join the RNA nucleotides and the RNA pulls away and leaves the nucleus.DNA zips back up.

mRNA Editing

Exons-left inIntrons-cut out

Noncoding segments called introns are spliced outA cap and a tail are added to the ends

Translation (Protein Synthesis)

Where? At a ribosome in the cytoplasmWhat? enzymes and energy, mRNA, tRNA, rRNA, amino acids

Transfer RNA molecules serve as interpreters during translation

In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptideThe process is aided by transfer RNAs

Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other

Ribosomes (rRNA)

mRNA, a specific tRNA, and the ribosome subunits assemble during initiation

Translation

First a small ribosomal subunit joins mRNA at a start codon-AUG. The appropriate tRNA comes to join the mRNA. Large ribosomal sub unit joins.

Another tRNA comes bringing the correct amino acid with it. A peptide bond forms between the amino acids, and the 1st tRNA leaves.

Translation

First a small ribosomal subunit joins mRNA at a start codon-AUG.

The appropriate tRNA comes to join the mRNA. Large ribosomal sub unit joins.

Another tRNA comes bringing the correct amino acid with it. A peptide bond forms between the amino acids, and the 1st tRNA leaves.

This continues until a stop codon (UGA, UAG, UAA) is reached. Then all break apart and a polypeptide is released.

Mutations

Good, bad, or who cares?Substitution-redundancyDeletion or InsertionFrameshift

SpontaneousMutagensHigh energy radiation

X rays, UV lightChemicals

Viruses-DNA or RNA in a protein coat

RNA viruses-retrovirusesReverse transcriptaseLytic cycleLysogenic

Viruses of concern

EbolaHantaHIVAvian (Bird) fluInfluenza 203AIDS 205

Differentiation

Cancer results from mutations in genes that control cell division.

OncogenesProto-oncogenes

Colon Cancer

Recombinant Genetics

Gel Electrophoresis

Separates fragments by their size