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 Pyrimidines and Purines

DNA has four kinds of bases, A, T, C, and G thymine cytosine adenine guanine pyrmpyrm

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 DNA Ribose-deoxyribose RNA is single stranded and DNA is double stranded Uracil 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 1 st 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 1 st 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

Spontaneous Mutagens High energy radiation X rays, UV light Chemicals

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