Unit 7 Molecular Genetics

October 29, 2009 What is DNA? Agenda: 1. Discuss the history of DNA HW: Missing work due FRIDAY Georgia Performance Standards: SB2: Passing on Biological Traits

DNA and RNA I. DNA- deoxyribonucleic acid A. History of DNA as Genetic Material “code of life” 1. Griffith and Transformation 1928 a. Frederick Griffith made discovery while investigating bacteria known to produce pneumonia b. Griffith isolated two different strains of bacteria

1). Disease causing strain- had (S) smooth edges. When injected into mice caused pneumonia. 2 ). Harmless strain- grew with (R) rough edges. 3). When disease causing bacteria heated- mice survived when injected 4). Mixed the heated-killed bacteria and harmless ones. When injected caused pneumonia. Concluded that one strain had been changed into another. Called transformation (another organism takes up outside DNA.).

Molecular Genetics Avery  Identified the molecule that transformed the R strain of bacteria into the S strain  Concluded that when the S cells were killed, DNA was released  R bacteria incorporated this DNA into their cells and changed into S cells DNA: The Genetic Material Chapter 12  Concluded that DNA was transforming factor- carries the genetic code

Molecular Genetics Hershey and Chase Showed conclusively that DNA was molecule that carried genetic code DNA: The Genetic Material Chapter 12 Studied viruses known as Bacteriophages (virus that infects bacteria)

Bacteriophage

Used different radioactive markers to label DNA and proteins of bacteriophages

Chargaff’s Rule- ratio of guanine:cytosine and adenine:thymine are equal A = T and G = C Erwin Chargaff- 1950

Molecular Genetics X-ray Diffraction  X-ray diffraction data helped solve the structure of DNA 12.1 DNA: The Genetic Material Chapter 12  1950’s Rosalind Franklin used X-ray diffraction to study structure of DNA molecule. Concluded structure was coiled like a spring (helix)

 Indicated that DNA was a double helix X-ray Diffraction cont’d…

Molecular Genetics Watson and Crick  After looking at Franklin and Wilkin’s work, Watson and Crick constructed a model of DNA molecule (1953) 12.1 DNA: The Genetic Material Chapter 12

Journal Entry October 30, In 1928 Griffith demonstrated the transformation of a.R bacteria into S b. S bacteria into R bacteria c. heat killed S bacteria into R bacteria 2. Hershey & Chase used bacteriophages and radioactive markers to determine genetic material is made of: a.Protein b. RNAc. DNA 3. Watson & Crick constructed a model of DNA with the configuration of a a.Single helixb. Double helixc. Triple helix 4. Chagaff’s observations established the specific _____________ rule of DNA a.Geneticb. Bondingc. Base pairing 5. Avery’s experiments demonstrated that DNA: a.Makes proteins b. is genetic materialc. is found in bacteriophages 6. The work of Chargaff and Franklin formed the basis for what scientist(s) discovery?

What is DNA? Agenda: 1. Discuss DNA Structure 2. Complete DNA History and Structure Worksheet Georgia Performance Standards: SB2: Passing on Biological Traits

Molecular Genetics DNA Structure  Nucleotides  Consist of a  five-carbon sugar  a phosphate group  a nitrogenous base 12.1 DNA: The Genetic Material Chapter 12

Base Groupings Purines (Double ringed) 1.Adenine 2.Guanine Pyrimidines (Single ringed) 1.Cytosine 2.Thymine

Backbone of DNA chain formed by sugar and phosphate groups of nucleotides sugar phosphate

Molecular Genetics DNA Structure  DNA often is compared to a twisted ladder.  Rails of the ladder are represented by the alternating deoxyribose and phosphate.  The pairs of bases (cytosine–guanine or thymine–adenine) form the steps DNA: The Genetic Material Chapter 12

Journal Entry November 2, What sugar makes up the “backbone” of DNA? a.Glucoseb. Ribosec. Deoxyribose 2. What macromolecule do we consider DNA and RNA to be? a.Proteinb. Nucleic Acidc. Carbohydrate 3. What type of bonds hold the bases together in DNA?\ a.Hydrogenb. Covalentc. Ionic 4. What do we call the repeating units that make up DNA? a.Phosphate b.Nitrogenous Basec. Nucleotides 5. Pyrimidines are _____________ ringed structures and purines are ____________ ringed structures. a. single, tripleb. double, singlec. single. double 6. What 3 things make up a nucleotide?

November 2, 2009 How are chromosomes formed? Agenda: 1. Introduce DNA Replication 2. Review DNA Structure HW: Complete DNA Structure Worksheet Georgia Performance Standards: SB2: Passing on Biological Traits

12.1 DNA: The Genetic Material Molecular Genetics Chromosome Structure  DNA coils around histones to form nucleosomes, which coil to form chromatin fibers. Chapter 12

Quick Molecular Genetic Terminology Replication= DNA  DNA Transcription= DNA  RNA Translation= RNA  Amino Acids Polypeptide= Chain of amino acids Adenine, cytosine, & guanine= DNA & RNA Thymine= DNA Only Uracil= RNA Only

12.2 Replication of DNA Molecular Genetics Replication  Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA. Semiconservative Replication Chapter 12

Molecular Genetics Unwinding  DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix.  Single stranded binding proteins hold the DNA open  RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand Replication of DNA

Molecular Genetics Joining  DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.  DNA ligase links the sections on lagging strand called Okazaki Fragments Replication of DNA Chapter 12

27 Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’

28 Answer: DNA 5’-CGTATG-3’ DNA 3’-GCATAC-5’

12.2 Replication of DNA Molecular Genetics Comparing DNA in Eukaryotes and Prokaryotes  Eukaryotic DNA located in cells nucleus in form of a number of chromosomes  Replication occurs at multiple sites.  In prokaryotes, the circular DNA strand is opened at one origin of replication. Chapter 12

12.3 DNA, RNA, and Protein Molecular Genetics Central Dogma: DNA makes RNA makes protein  RNA  Contains the sugar ribose and the base uracil  Usually is single stranded Chapter 12

Molecular Genetics Messenger RNA (mRNA)  Strands of RNA nucleotides that are complementary to one strand of DNA Ribosomal RNA (rRNA)  Helps join the mRNA codons to the tRNA anticodons in the ribosome Transfer RNA (tRNA)  Transport amino acids to the ribosome 12.3 DNA, RNA, and Protein Chapter 12

Molecular Genetics 12.3 DNA, RNA, and Protein Chapter 12

 DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mRNA will be synthesized. Molecular Genetics Transcription  DNA to mRNA 12.3 DNA, RNA, and Protein Chapter 12

Molecular Genetics The Code  DNA code is a three-base code.  The three-base code in mRNA is called a codon DNA, RNA, and Protein Chapter 12

Molecular Genetics Translation  RNA  Amino Acid  In translation, tRNA molecules act as the interpreters of the mRNA codon sequence.  Each anticodon (on tRNA) is complementary to a codon (on mRNA) DNA, RNA, and Protein Chapter 12

64 possible codons 20 different amino acids Codons

Start Codon AUG Stop Codons UGA UAA UAG

Molecular Genetics

Extra Facts Genes give instructions for making proteins It is possible for more than one combo of codons to code for the same amino acid because there are 64 different types of codons, but only 20 amino acids Takes 3 bases to code for 1 amino acid

Molecular Genetics RNA Processing  The code on the DNA is interrupted periodically by sequences that are not in the final mRNA.  Intervening sequences are called introns.  are cut out by enzymes  The portions of DNA molecules that actually code for the production of proteins are called exons.  parts of the mRNA that are kept and expressed 12.3 DNA, RNA, and Protein Chapter 12

Molecular Genetics Mutations  A permanent change that occurs in a cell’s DNA 12.4 Gene Regulation and Mutation Chapter 12  2 Main Types of Mutations:  Gene  Chromosomal

Molecular Genetics Causes of Mutation  Can occur spontaneously  Chemicals and radiation such as X rays and gamma rays 12.4 Gene Regulation and Mutation Chapter 12

Molecular Genetics Body-cell v. Sex-cell Mutation  Somatic cell mutations are not passed on to the next generation.  Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring Gene Regulation and Mutation Chapter 12

Gene mutations Point mutations – mistakes with 1 nucleotide –Substitution of the wrong nucleotide (nitrogen base) in place of correct one Frameshift mutations – occur when a nucleotide is either inserted or deleted, altering the codon sequence –More severe than point mutations because it affects all of the amino acids in the protein

Chromosomal mutations Change in the number or structure of the chromosomes –Duplication –Inversion –Translocation

Molecular Genetics 12.4 Gene Regulation and Mutation Chapter 12