Molecular Genetics Glencoe Chapter 12

DNA: The Genetic Material Griffith-first major experiment that led to the discovery of DNA as genetic material Worked with two strains of bacteria and found that one could be transformed into another

DNA: The Genetic Material Avery-identified transformation molecule as DNA Hershey and Chase-definite evidence that DNA is the transforming factor Used radioactive labeling to trace DNA and protein

DNA: The Genetic Material X-ray diffraction- aims X-ray at DNA molecule Indicated double helix structure Twisted ladder shape Rosalind Franklin

DNA: The Genetic Material Watson and Crick Used Franklin’s photo Measured width of helix and spacing of bases to build a model of double helix

DNA: The genetic material DNA structure Nucleotides: subunits of nucleic acids that consist of a five carbon sugar, a phosphate group, and a nitrogenous base DNA: adenine (A), guanine (G), Cytosine (C), Thymine (T) RNA: adenine (A), guanine (G), Cytosine (C), Uracil (U)

DNA: The Genetic Material Chargaff’s rule A=T, G=C

DNA: The Genetic Material Sugar phosphate backbone Antiparallel strands-one strand runs 5’3’ and other runs 3’5’

DNA: The Genetic Material

DNA: The Genetic Material Chromosome Structure 51 million-245 million base pairs DNA coils around histones to form a nucleosome Phosphate groups in DNA create negative charge Histones are positively charged Nucleosomes group in chromatin fibers then coil

Replication of DNA

Replication of DNA Helicase-unwinds DNA RNA primase-adds short segment of RNA called primer DNA polymerase-adds nucleotides to the 3’ end

Replication of DNA Leading strand-built continuously Lagging strand-built discontinuously in segments called Okazaki fragments

Replication of DNA Joining Ligase

Replication of DNA

DNA, RNA and Protein Central Dogma DNARNAprotein DNA Transcription Figure 10.6A DNA Transcription RNA Protein Translation Central Dogma DNARNAprotein

DNA, RNA and Protein RNA Single stranded Contains sugar ribose Base uracil replaces thymine

DNA, RNA and Protein RNA

DNA, RNA and Protein Transcription-DNA code is transferred to mRNA in the nucleus DNA is unzipped and RNA polymerase binds and adds nucleotides to 3’ end

DNA, RNA and Protein Transcription Initiation Elongation Termination RNA polymerase DNA of gene Promoter DNA Terminator Area shown In Figure 10.9A Growing RNA Completed RNA polymerase Figure 10.9B Transcription Initiation Elongation Termination 1 Initiation 2 Elongation 3 Termination

DNA, RNA and Protein RNA processing Exon Intron Exon Intron Exon DNA Cap Transcription Addition of cap and tail RNA transcript with cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence Nucleus Cytoplasm RNA processing Introns-segments not in the final mRNA Exons-sequences that remain in final mRNA 5’ cap and poly-A tail

DNA, RNA and Protein Genetic code Codon- 3-base code for amino acids in mRNA

DNA, RNA and Protein tRNA Attached to amino acids Has anticodon complementary to codons on mRNA

DNA, RNA and Protein Ribosome 2 subunits EPA sites

DNA, RNA and Protein Translation mRNA leaves nucleus and associates with ribosomal subunits tRNAs add their amino acids to polypeptide chain as mRNA moves through the ribosome one codon at a time Stops when stop codon is reached

DNA, RNA and Protein

Gene Regulation and Mutation Prokaryote Gene Regulation Gene regulation-ability for an organism to control which genes are transcribed Operon- section of DNA that contains gene for proteins needed for a specific metabolic pathway Operator-acts as on/off switch for transcription Promoter-where RNA polymerase first binds regulatory gene genes coding for proteins

Gene Regulation and Mutation trp operon Cluster of genes coding for production of tryptophan Repressible operon- transcription is normally turned off When tryptophan is present, no need to produce more

Gene Regulation and Mutation Tryptophan binds to repressor protein which binds to the mRNA, blocking RNA polymerase from binding With low levels of tryptophan, repressor will not bind to mRNA and genes will be transcribed.

Gene Regulation and Mutation lac operon When lactose is present, makes enzymes to use lactose as energy source Inducible operon Repressor protein inactive when bound to lactose

Gene Regulation and Mutation Eukaryotic gene regulation Transcription factors-proteins that ensure that a gene is used at the right time and that proteins are made in the right amounts One set guide and stabilize RNA polymerase Another set help control rate of transcription Activators and repressors Complex structure and coiling inhibits transcription

Gene Regulation and Mutation Hox genes-responsible for general body pattern Genes that control differentiation,

Gene Regulation and Mutation Mutation-permanent change made to a cell’s DNA Point mutation-change in one base pair Substitution Missense-changes one amino acid Silent-does not change the amino acid Nonsense-changes to a stop codon Insertion-gain of nucleotides Deletion-loss of nucleotides Frame shift-caused by deletion or insertion, changes reading frame

Gene Regulation and Mutations Causes of mutations DNA polymerase adding wrong nucleotides Has proofreading system, very uncommon Mutagens-substances (chemicals, radiation) that cause mutations by changing chemical structure of bases