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Chapter 12. DNA and RNA. 12-1 DNA. What is a gene? A sequence of DNA that codes for a protein that determines a trait What is DNA? Deoxyribonucleic acid DNA is the chemical structure that makes up a gene. DNA discoveries. Griffith Studied pneumonia- harmless strain + harmful strain

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chapter 12
Chapter 12


12 1 dna
12-1 DNA
  • What is a gene?
    • A sequence of DNA that codes for a protein that determines a trait
  • What is DNA?
    • Deoxyribonucleic acid
    • DNA is the chemical structure that makes up a gene
dna discoveries
DNA discoveries
  • Griffith
  • Studied pneumonia- harmless strain + harmful strain
  • Killed harmful strain and mixed with harmless
  • Mice still got sick!
  • Conclusion: disease-causing ability was inherited
  • Transformation: process by which one strain of bacteria is changed by a gene or genes into another
dna discoveries1
DNA discoveries
  • But HOW was it inherited?
  • Avery
  • Made extract (“juice”)from harmful bacteria
  • Treated it to kill certain macromolecules
  • Transformation still happened
  • Treated it to kill DNA
  • No transformation
  • Conclusion: nucleic acid (DNA!) responsible for transformation
dna discoveries2
DNA discoveries
  • Hersheyand Chase
  • Studied viruses
  • Bacteriophage: virus that infects bacteria
  • Made up of protein coat and DNA
    • which carries genetic material?
  • Conclusion: DNA does!
4 criteria for a gene
4 Criteria for a gene:
  • 1. must be able to store info. and be able to carry it from one generation to the next
  • 2. must be strong and stable so it doesn’t break down
  • 3. must be easily copied
  • 4. must be able to mutate- variation allows for adaptation to occur
dna structure
DNA Structure
  • What are the monomers of nucleic acids?
    • Nucleotides
  • Nucleotides made up of 3 parts:
    • 5 C sugar
    • Phosphate group
    • Nitrogenous bases
      • Adenine (A)
      • Guanine (G)
      • Cytosine (C)
      • Thymine (T)
structural discoveries
Structural discoveries
  • Chargoff- base pairing
    • A = T and C = G
  • Rosalind Franklin- x-ray diffraction
    • showed “x” shape pattern
  • Watson and Crick
    • Double helix (“twisted ladder”)
    • H bonds between bases
dna origami
DNA origami!
12 2 chromosomes and dna replication
12-2 chromosomes and dna replication
  • Where is our DNA?
  • Eukaryotes- nucleus
    • multiple chromosomes
  • Prokaryotes- cytoplasm
    • usually 1 chromosome
dna structure1
Dna structure
  • VERY long
  • Ex: E. Coli has 1 chromosome
  • Like fitting 300m of rope in a backpack
  • Nucleus of a human cell has ~1 meter of DNA
  • How does it fit?
chromosome structure
chromosome structure
  • Chromosomes made up of…
  • Chromatin: DNA coiled around protein (histones)
  • Form a nucleosome- continue folding DNA in nucleus (coils and supercoils)
dna replication
Dna replication
  • Replication: process by which a cell duplicates it’s DNA
  • WHY do we replicate DNA?
    • Mitosis
    • Meiosis
dna replication1
Dna replication
  • Step 1: two strands separate
  • Enzyme helicase “unzips” the double helix
    • break H bonds
  • Creates 2 replication forks
dna replication2
DNA Replication
  • Step 2: base pairing creates complimentary strands
    • Half old/half new
  • Enzyme DNA polymerasejoins individual nucleotides forming a polymer
  • proofreading
dna replication3
DNA replication
12 3 rna and protein synthesis
12-3 RNA and Protein synthesis
  • Gene: a sequence of DNA that codes for proteins that determine a trait
  • What does protein synthesis mean?
    • Making proteins!
  • “code” = nucleotide sequence
  • Must first turn DNA into RNA
  • Ribonucleic acid
  • RNA Structure:
    • Single stranded
    • Ribose sugar
    • Phosphate group
    • Nitrogenous bases
      • Uracil in place of thymine (U in place of T)
3 types of rna
3 Types of RNA
  • ALL involved in protein synthesis
  • 1. Messenger RNA (mRNA)
    • Carries copies of instructions to make proteins from DNA to rest of cell
  • 2. Ribosomal RNA (rRNA)
    • Make up ribosomes
  • 3. Transfer RNA (tRNA)
    • Transfers amino acids to ribosomes during protein synthesis
protein synthesis
Protein synthesis
  • Involves transcription and translation
  • Transcription: copying DNA sequence into RNA sequence
  • Translation: using mRNA to code for a protein
  • DNA separated into 2 strands
  • RNA polymerase (enzyme)-uses each strand as a template to build complementary RNA strand
    • (similar to DNA polymerase)
  • Promoter region- specific sequence of bases that tells where to start building RNA strand
rna editing
Rna editing
  • RNA polymerase also proofreads + corrects mistakes
  • Exons: nucleotides that code for proteins
    • “express proteins”
  • Introns: nucleotides NOT involved in protein synthesis
    • These are “cut” out
the genetic code
The genetic “code”
  • What are the monomers of proteins?
    • Amino acids! (aa)
  • RNA has 4 possible bases (A, U, C and G)
  • 3 bases = codon: code for a specific aa
  • aa are added together to make a protein polymer
  • “start” and “stop” codons
  • Ribosomes “read” the code for the protein
    • “Expression”
  • 1. mRNA attaches to ribosome
  • 2. codons code for an aa
    • tRNA brings aa to ribosome- add to chain
      • Peptide bonds
    • Anticodon- part oftRNA- complimentary to mRNA codon
  • 3. continue until “stop” codon
protein synthesis1
Protein synthesis
roles of d na and r na
Roles of Dna and Rna
  • DNA: like a master plan
    • stay safe in the nucleus
  • RNA: like a blue print copy
    • disposable
genes and proteins
Genes and proteins
  • What does protein have to do with traits?
    • Genes: code for protein that determines a trait!
  • Proteins are microscopic tools that build parts of living things
    • What we look like
  • Many proteins are enzymes- catalyze chemical reactions
    • How we function
vocabulary quiz review
Vocabulary quiz review
  • The type of RNA that carries instructions to make proteins from DNA to the rest of the cell
    • Messenger RNA (mRNA)
  • A sequence of DNA that codes for a protein that determines a trait
    • Gene
  • The type of protein that DNA coils around to make chromatin
    • Histone
  • The enzyme used to create the new strand of DNA during replication
    • DNA polymerase
vocabulary quiz review1
Vocabulary quiz review
  • A sequence of nucleotides that are involved in protein synthesis
    • Exon
  • A 3 base sequence of nucleotides that code for an amino acid
    • Codon
  • A 3 base sequence of nucleotides found on tRNA that are complimentary to a codon
    • Anticodon
  • A region of DNA that signals RNA polymerase to start building the RNA strand
    • Promoter region
vocabulary quiz review2
Vocabulary quiz review
  • This is the process of copying a DNA sequence into an RNA sequence
    • Transcription
  • This is the process of using mRNA to code for a protein
    • Translation
  • This is the process where one strain of bacteria is changed into another strain by altering a gene or genes
    • Transformation
  • The rule that, in DNA, cytosine can only bond to guanine and adenine can only bond to thymine
    • Complimentary base pairing
12 4 mutations
12-4 mutations
  • Mutations: changes in genetic material
  • Gene mutations: changes in single gene
  • Chromosomal mutations: changes in whole chromosomes
gene mutations
Gene mutations
  • Point mutations: involve 1 or a few nucleotides
    • Effect 1 aa
    • Types: Substitutions, insertions, deletions
  • Frameshift mutations: a shift in the entire reading frame
    • Effects all aa
    • Protein may be unusable
chromosomal mutations
Chromosomal mutations
  • Types:
  • Deletion- loss of all/part of a chromosome
  • Duplication- extra copies of a chromosome
  • Inversion- reverse direction of the chromosome
  • Translocation- part of a chromosome breaks off and joins a different one
significance of mutations
Significance of mutations
  • Most are harmless/neutral
  • Some change proteins structure/expression- cause damage
    • Cancer and other disorders
  • Some are beneficial
    • Ex: polyploidy plants- have extra sets of chromosomes- are usually stronger
12 5 gene regulation
12-5 gene regulation
  • Genes are “turned on and off” as needed
  • Expression: when a gene is turned on, and the protein is coded for
  • Not all genes expressed at once
  • Prokaryotes and eukaryotes regulate differently
lac operon example
Lac operon example
  • Prokaryote gene regulation
  • Operon: a group of genes working together
  • Regulatory sites (aka: operator): site where proteins bind to regulate transcription
  • Lac operon genes- used by E. coli to break down lactose for food
  • When lactose is present, gene turned “on”
  • When no lactose present, protein binds to operator, turning gene “off”
eukaryote gene regulation
Eukaryote gene regulation
  • More complex- usually no operons
  • TATA box- sequence of nucleotides tells RNA polymerase where to go and what to express
  • Only express what is needed
development and differentiation
Development and differentiation
  • Differentiation: when cells become specialized in structure and function
  • Hox genes controls differentiation in cells, starting in the embryo
hox gene manipulations
Hox gene manipulations
  • Hox genes can be manipulated
    • Ex: gene for antenna replaced with gene for leg
      • You get a leg on the fly’s face!
  • Common ancestry= ability to manipulate across species
    • Ex: gene for mouse eye + gene for fly leg = eye on fly’s leg
real life gene regulation issue teratoma
REAl life gene regulation issue- teratoma