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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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Dna rna and protein synthesis ch 10

DNA, RNA and Protein Synthesis= CH 10

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

Griffith s experiments1

Griffith’s Experiments

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


Dna structure

DNA Structure

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

DNA Replication

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

Dna rna and protein synthesis ch 10

  • 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

Dna rna and protein synthesis ch 10

  • - 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

Controlling transcription in eukaryotes

Controlling Transcription in Eukaryotes

Removal of introns after transcription

Removal of Introns After Transcription

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

Genetic engineering and biotechnology ch 13

Genetic Engineering and Biotechnology = Ch 13

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

Dna fingerprinting

DNA Fingerprinting

Dna fingerprinting1

DNA Fingerprinting

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

Restriction enzymes1

Restriction Enzymes

Producing restriction fragments

Producing Restriction Fragments

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

Producing combining restriction fragments

Producing & combining restriction 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?

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