Dna rna and protein synthesis ch 10
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DNA, RNA and Protein Synthesis= CH 10. Griffith’s Experiments. Showed that hereditary material can pass from one bacterial cell to another The transfer of genetic material from one cell to another or organism to organism is called transformation

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Griffith s experiments
Griffith’s Experiments

  • Showed that hereditary material can pass from one bacterial cell to another

  • The transfer of genetic material from one cell to another or organism to organism is called transformation

  • Heat killed virulent bacteria can transfer their disease causing ability to harmless bacteria

Avery s experiments
Avery’s Experiments

  • Showed that: DNA is the hereditary material that transfers info btwn bacterial cells

  • Cells missing RNA and Protein could transform R into S cells

  • Cells missing DNA could not transform cells

Hershey chase experiment
Hershey-Chase Experiment

  • DNA not protein is the genetic material

  • DNA of viruses enters bacterial cells and this causes the bacterial cell to produce more viruses containing DNA

  • Protein doesn’t enter cells

Discovery of structure
Discovery Of Structure

  • 1953: Watson and Crick put together a model of DNA using Franklin’s and Wilkins’s DNA diffraction X-rays

Molecular structure of dna
Molecular Structure of DNA

  • DNA is composed of 2 strands made of 4 kinds of nucleotides

  • Each nucleotide consists of 3 parts:

    • one 5-carbon sugar (deoxyribose)

    • one phosphate group, and

    • one of 4 bases

      • adenine (A), guanine (G), thymine (T), cytosine (C).

Structure of a nucleotide
Structure of a nucleotide

  • Sugar & Phosphate are “sides” of ladder and Bases are the “rungs” & attach to sugars

2 categories of dna bases purines vs pyrimidines
2 categories of DNA bases:PurinesvsPyrimidines



= PuAG



= PyTC

Purines vs pyrimidines
Purines vs Pyrimidines

  • Chargaff showed that

    • % of A always = % of T

    • % of G always = % of C

  • Purines always with pyrimidines


Complementary base pairing rules
Complementary base pairing rules

  • Base pairs are formed by hydrogen bonding of A with T (2 H bonds), and

    G with C (3 H bonds)

Dna replication in s phase of cell cycle
DNA Replication = inS phase of cell cycle

  • An enzyme (helicase) breaks the H bonds between base pairs and unZIPS the strands = replication fork

Dna replication1
DNA Replication

  • Another enzyme (DNA polymerase) attaches the complementary base to the original DNA strand

Dna replication2
DNA Replication

  • Results in DNA molecules that consist of one "old" strand and one "new" strand

  • Known as semi-conservative replication b/c it conserves the original strand).

Dna errors in replication
DNA Errors in Replication

  • Changes = mutation

  • Proofreading & repair prevent many errors

  • Unrepaired mutation can cause cancer

Flow of genetic material dna rna proteins
Flow of Genetic Material:DNA → RNA → Proteins

Rna structure
RNA Structure

  • RNA differs from DNA

    • RNA uses ribose as the sugar

      not deoxyribose.

    • RNA bases are

      A, G, C, and uracil (U).

      • G-C

      • A-U

    • Single Stranded

    • Shorter than DNA

    • Can Leave the nucleus

3 types of rna
3 Types of RNA

  • rRNA - ribosomal

  • mRNA - messenger

  • tRNA - transfer

Messenger rna mrna
Messenger RNA (mRNA)

  • Made from DNA in nucleus using RNA Polymerase

  • Is the “Blueprint" for a protein

    • Carried to ribosomes in cytoplasm after “stop” is reached

  • Carries message from nucleus to cytosol

Ribosomal rna rrna
Ribosomal RNA (rRNA)

  • rRNA + protein makes a ribosome

  • Site where proteins are assembled in cytoplasm

Transfer rna trna
Transfer RNA (tRNA)

  • Carries correct AA to ribosome/ mRNA complex


  • DNA → RNA

    • uses RNA Polymerase (binds at “promoter” region)

    • Process similar to DNA replication

    • Begins with a START codon and ends with a STOP codon

  • Makes rRNA, tRNA or mRNA

  • Message is “transcribed” from DNA code to RNA code

Protein synthesis translation
Protein Synthesis: Translation

  • Making of protein at the rRNA using mRNA and tRNA

  • Each base triplet in mRNA is called a codon

    -specifies an amino acid to be included into a polypeptide chain

    • Uses genetic code to determine amino acid

Genetic code
Genetic Code

  • Universal for all forms of life

    • 61 triplets specifying amino acids

    • 3 “stop” codes

  • Stop codes = UAA, UAG, UGA

  • StartCodon = AUG = methionine

From dna to proteins
From DNA to Proteins



  • mRNA leaves nucleus goes to ribosome

  • Begins when ribosome attaches to start codon

  • tRNA gets specific amino acid (floating free in cytosol), anticodon matches codon of mRNA and A.A.

  • tRNA brings its AA to ribosome and attaches it to growing chain of AA (protein)

  • stops at “stop” codon

Chapter 11 gene expression turn on genes to regulate protein and gene expression

Role of gene expression
Role of Gene Expression

  • Activation of a gene that results in transcription and production of mRNA

  • Only a fraction of a cell’s genes are expressed at any one time

    • You only express genes or make proteins when NEEDED!

Gene expression in prokaryotes

Gene Expression in Prokaryotes

-Studies in 1960’s by French scientists

-Started with simple intestinal prokaryotic cell= Escherichia coli = E. coli

  • Bacteria adapt to changes in their surroundings by using proteins to turn groups of genes on and off in response to various environmental signals

  • The DNA of Escherichia coli is sufficient to encode about 4000 proteins, but only a fraction of these are made at any one time. E. coli regulates the expression of many of its genes according to the food sources that are available to it

  • - Scientists discovered how genes in this bacteria metabolize lactose when present

  • -lactose = disaccharide…needs to be broken down into galactose and glucose

Gene expression in prokaryotes1
Gene Expression in Prokaryotes

  • When lactose is absent, E. coli will not produce the protein…is repressed

  • When lactose is present, E. coli will produces the 3 structural enzymes

    • Meaning this will make the “protein” or go through induction…..so it can break down lactose!

Gene expression in prokaryotes2
Gene Expression in Prokaryotes

  • http://www.phschool.com/science/biology_place/biocoach/lacoperon/genereg.html


Gene expression in prokaryotes3
Gene Expression in Prokaryotes

  • Operon: series of genes coding for specific products = “lac” operon

  • Operon = structural genes + promoter + operator

Gene expression in prokaryotes4
Gene Expression in Prokaryotes

  • Promoter: segment of DNA recognized by RNA polymerase which then starts transcription

  • Operator: segment of DNA that acts as “switch” by controlling the access of RNA polymerase to promoter

Prokaryotic on off switches
Prokaryotic On & Off switches

  • Transcription can be turned “on or off” depending on what the cell needs

  • When turned “off” a repressor protein is bound to DNA in front of the gene

  • To turn a gene “on” an inducer (lactose) binds to the repressor, causing it to fall off….then gene is expressed



Gene expression in eukaryotes
Gene Expression in Eukaryotes

  • Have not found “operons” in eukaryotes

  • Genomes are larger & more complex

  • Organized into introns and exons

    • Through removal of introns from pre- mRNA

Eukaryotic genes are made of introns and exons
Eukaryotic Genes are made of introns and exons

  • Intronsnoncoding portions of the gene, removed by enzymes before mRNA leaves the nucleus (pre-mRNA)

  • Exons portions that will eventually be translated remain in the finished mRNA that leaves the nucleus.

Gene expression in development
Gene Expression in Development

  • Expressed Genes: have been transcribed & translated

  • Cell Differentiation: Development of cells w/ different functions

  • Morphogenesis: development of form in an organism

  • Homeotic genes (hox): determine where anatomical structures

    (appendages) will develop

    & controls differentiation

    in early development

Gene expression in development1
Gene Expression in Development

  • Homeobox Sequence:

    • w/in homeotic genes

    • Sequence of DNA that regulates patterns of development

    • Homeoboxes of

      many diff eukaryotic

      organisms appear

      to be very similar

Gene expression cancer
Gene Expression & Cancer

  • Oncogene: Gene that causes cancer

  • Proto-oncogene = normal gene, regulates cell growth. May mutate into oncogene that may lead to cancer

  • Tumor-supressor gene (3 types): for protein that prevents uncontrolled cell division, mutation may stop this protein production

  • Viruses may have oncogenes or trigger them in another cell


  • Continue to divide indefinitely, even if too tightly packed or detach from other cells

  • Tumor: uncontrolled, abnormal cell division

  • benign tumor: does not migrate to other areas, usually harmless

  • malignant tumor: invade other healthy tissues = cancer

  • metastasis: breaking away and spreading to other body parts to form new tumors

Causes of cancer
Causes of Cancer

  • Carcinogen

    • Chemicals in tobacco smoke, asbestos, UV light from the sun

    • Mutagen: causes a mutation

Kinds of malignant tumors
Kinds of Malignant Tumors

  • Carcinoma: in skin & tissue lining organs

  • Sarcoma: in bone & muscle tissue

  • Lymphoma: in tissues that form blood

  • Leukemia: uncontrolled production of white blood cells

Causes of cancer1
Causes of Cancer

  • Mutations that change expression of genes coding for growth factor proteins

  • Usually comes after exposure to carcinogen (tobacco, UV light etc.)

  • usually need more than 1 mutation to get cancer

Dna identification fingerprinting
DNA Identification/fingerprinting

  • Gene = segment of DNA bases that code for traits and proteins

  • Genetic engineering= use of genes to create or modify the genome

  • DNA fingerprinting = The repeating sequences in noncoding DNA (introns) vary between individuals & thus be used to identify an individual

Steps in dna identification fingerprinting
Steps in DNA identification (fingerprinting)

  • Gel electrophoresis: pieces are separated by size on a gel creating “bands” = fingerprint

  • Everybody has different number and size of pieces because their DNA sequences are different

  • PCR = polymerase chain reaction = duplicate DNA

    • cut “digest” DNA with restriction enzyme to get a bunch of pieces

Gel electrophoresis
Gel Electrophoresis

  • DNA fragments placed into “wells” in gel agarose

  • Electricity pulls on DNA fragments, DNA is “-” and thus goes toward “+” side

  • Fragments travel at different rates based on size and ability to squeeze through swiss-cheese-like agarose

Polymerase chain reaction pcr
Polymerase Chain Reaction (PCR)

  • Useful if you only have a little bit of DNA and need to make copies of it

  • Crime scenes, genetic disorders in embryonic cells, study ancient DNA fragments

Restriction enzymes
Restriction Enzymes

  • Cuts DNA at specific base sequence

  • Produces sticky ends

  • Recombinant DNA = Complementary sticky ends can be fused together…is recombined

Producing restriction fragments
Producing Restriction Fragments

  • DNA ligase enzyme used to splice together cut plasmids and chromosome fragments


  • Making identical copies of cells

  • Can clone genes or organisms

  • Cloning a Gene= making large quantities of a desired DNA piece …usually insert into a vector (bacteria)

  • Transfers gene between organisms

  • Plasmids: circle of DNA in bacterium replicates independently of the single main chromosome

Transplanting genes
Transplanting Genes

  • Gene may be used to make bacteria produce specific protein - insulin production

Stem cells
Stem Cells

  • Stem cells have the ability to

    • divide and renew themselves

    • remain undifferentiated in form

      3. develop into a variety of specialized cell types

Genomic library
Genomic Library

  • Includes all pieces of genome that come from cutting with a particular restriction enzyme

  • Can have multiple libraries for the same organism - all cut with different R.E.’s

Transgenic organism
Transgenic Organism

  • The host that has received the recombinant DNA

  • Organism produces the new protein unless the gene gets “turned off”

  • Keep gene “turned on” by splicing it in near a gene that is frequently expressed

Human genome project
Human Genome Project

  • Sequence entire human genome

  • Began in 1990 - expected completion was 2005, but it was completed in 2000

  • Thought humans had 100,000 genes, but its fewer than 30,000

  • We have the sequence of genes, but don’t know what they all do yet

  • Use info for diagnosis, treatment, prevention of genetic disorders

Future of genomics
Future of Genomics

  • Bioinformatics: Uses computers to catalog & analyze genomes

  • Proteomics: studies the identities, interactions, and abundances of an organisms proteins

  • Microarrays: two-dimensional arrangement of cloned genes, useful to compare specific proteins such as those that cause cancer

Medical applications
Medical Applications

  • Gene Therapy: Used on individuals to insert normal genes (or repair damaged DNA) into body cells to cure disease

    • Abnormal gene can still be inherited

  • Used on fertilized zygotes or embryos to insert normal genes for both developing body AND sex cells

    • Genome changed permanently

Uses of dna technology
Uses of DNA Technology

  • Cloning

  • Stem Cell Research

  • Pharmaceutical Products

    • insulin

  • Vaccines

    • work because body recognizes proteins, can produce protein without introducing pathogen

Uses of dna technology1
Uses of DNA Technology

  • Agricultural Crops

    • disease resistance

    • herbicide resistance

    • Improve nutrition

    • require less fertilizer (incorporate nitrogen fixing gene)

Concerns of dna technology
Concerns of DNA Technology

  • Plants might produce toxins that could cause allergies in people who consume them

Concerns of dna technology1
Concerns of DNA Technology

  • What if the plants get into the “wild” - forming “superweeds”

  • Do we really know what we are doing when we mix genes?