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DNA Chapter 10. The Code of Life. History Griffith Hershey and Chase Chargaff Linus Pauling Maurice Wilkins Rosalind Franklin Francis Crick James Watson. Model Double Helix Building Blocks-Nucleotides Sugar-Deoxyribose Phosphate Nitrogen Base. Types of Nitrogen Bases.

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DNA Chapter 10

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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 T

G 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? Nucleus

  • When? before cell division so that each cell can have a complete set of instructions

  • What? DNA, free nucleotides, enzymes and energy

  • Enzymes (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? Nucleus

  • Why? DNA wants to send out a message.

  • What? DNA, free RNA nucleotides, enzymes and energy

  • First, 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 in

Introns-cut out


  • Noncoding segments called introns are spliced out

  • A cap and a tail are added to the ends


Translation (Protein Synthesis)

Where? At a ribosome in the cytoplasm

What? 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 polypeptide

  • The 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-redundancy

  • Deletion or Insertion

  • Frameshift


SpontaneousMutagensHigh energy radiationX rays, UV lightChemicals


Viruses-DNA or RNA in a protein coat

RNA viruses-retroviruses

Reverse transcriptase

Lytic cycle

Lysogenic


Viruses of concern

  • Ebola

  • Hanta

  • HIV

  • Avian (Bird) flu

  • Influenza 203

  • AIDS 205


Differentiation


Cancer results from mutations in genes that control cell division.

Oncogenes

Proto-oncogenes


Colon Cancer


Recombinant Genetics


Gel Electrophoresis

Separates fragments by their size


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