DNA, RNA, Protein Synthesis Chapter 12

Discovery of DNA Protein or Nucleic acid Question (1928) –Which stored the genetic information? Frederick Griffith –Used mice and Streptococcus pneumoniae –Summary of his findings Treatment Affect on mouse S strain died R strain lived Heated S strain lived R stain w/ Heated S Strain died

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Griffith’s Experiment

Cont… Griffith concluded that information or factor was transferred from heated S strain to the live R stain. This process he called transformation. Oswald Avery- did the same experiment but also used an enzyme that destroyed carbohydrates, protein and lipids. Avery was able to show that it was nucleic acid not proteins that store genetic information

Structure of Nucleic Acid Edwin Chargaff- tested amounts of nitrogen bases in organism Edwin Chargaff- tested amounts of nitrogen bases in organism –Four types of bases Adenine, thymine, cytosine, guanine –Chargaff found that the amount of adenine was always the same as thymine, and guanine the same as cytosine

DNA is made up of Nucleotides Nucleotides –Five carbon sugar (deoxyribose) –A phosphate group –One Nitrogenous Bases AdeneineGuanineCytosineThymine Purine Pyrimidines

PurinesPyrimidines AdenineGuanineCytosineThymine Phosphate group Deoxyribose DNA Nucleotides Section 12-1

Watson & Crick Used knowledge of Chargaff experiments and X-ray imaging to discover some very important characteristics of DNA –Double stranded –Double helix –Sugar and phosphate make up backbone –Bases bind together (base pairing) Adenine to thymine Cytosine to Guanine

Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Structure of DNA Section 12-1

DNA Replication Remember this is done during the S phase of interphase in cell life cycle How it does it? –DNA unwinds (enzymes break the hydrogen bonds) –DNA polymerase enzyme attaches to each strand and uses free floating nucleotides to assemble complementary strand –This process continues until two complete copies of the DNA are made

DNA Replication Section 12-2 Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand

Chromosome Structures Strands of DNA are wrapped around proteins called histones –This is what makes up chromatin –During cell division this chromatin is packed tightly into chromosomes This is done to assist the genetic information in separating properly Also there is evidence to show the compact DNA can influence the expression of the genes

Chromosome Structure of Eukaryotes Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

Nondisjunction in Meiosis During anaphase a chromosome fails to separate thus one gamete will have two many of one chromosome and on will be short a chromosome. –Monsomy- zygote has one copy of chromosome –Trisomy-zygote has three copies of same chromosome Ex. Down syndrome is a trisomy on the 21 chromosome –Genotype may look like the following: (AAa, XXX, XXY, or XO)

Review of DNA Double stranded Double helix Base pairing –Adenine to Thymine –Cytosine to Guanine Replication prior to cell division

DNA and RNA Deoxyribose Nucleic Acid Double stranded Thymine Base Genetic information storage Ribonucleic Acid Single stranded Uracil Base instruct the making of proteins (protein synthesis) Three types –messengerRNA (mRNA) –transferRNA (tRNA) –ribosomalRNA (rRNA)

mRNA Makes a complimentary template of DNA sequence Codon-three-nucleotide sequence on mRNA that codes for an amino acids Amino Acids are the building blocks of proteins

Transcription: RNA Synthesis Process by which DNA is copied into a complementary strand of RNA Why must DNA do this? This process is a lot like replication but only short single stranded RNA is produced This process takes place in the nucleus of the cell

RNA DNA RNA polymerase Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only)

RNA splicing Introns – noncoding regions of DNA or RNA Exons- regions of DNA or RNA that do code for proteins Before mRNA leave the nucleus it splices or remove the introns and splices the exons together

Translation Decoding of mRNA into polypeptide chains (proteins) Ribosome attach to mRNA in the cytoplasm tRNA is now ready to attach amino acid to the ribosome tRNA anticodon matches up with mRNA codon to assemble the amino acids in correct order

Translation Section 12-3

Translation (continued) Section 12-3

Proteins Long chains of amino acids form what is called polypeptides Polypeptides combine to form protein molecules Proteins are what we see in our phenotype

Changes to DNA Mutations- random changes in nucleotide sequence of DNA –Chromosomal Mutations-involve entire chromosome (cancer) –Gene mutations- involve single individual genes

Chromosomal Mutations Deletion-occurs when chromosomes brake and a piece is lost Duplication- occurs when chromosome breaks off and is incorporated back into the chromosome, resulting is an extra copy Translocation- chromosome breaks off and attaches to different chromosome

Chromosomal Mutation cont… Inversion- chromosome break off, turns around, and reattaches in reverse order

Deletion Duplication Inversion Translocation Chromosomal Mutations Section 12-4

Gene Mutation Frameshift- deletion or addition that disrupts codons sequence See fig pg. 194 Point Mutation- occurs because of a substitution of a base pair –Only effect one codon