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Chapter 10: DNA

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Chapter 10: DNA Something to think about: Look around the room at your classmates. Observe how they vary in the shape of their front hair-line, the space between ... – PowerPoint PPT presentation

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Title: Chapter 10: DNA


1
Chapter 10 DNA
  • Something to think about
  • Look around the room at your classmates. Observe
    how they vary in the shape of their front
    hair-line, the space between their front teeth,
    the way in which their earlobes are attached to
    their head.
  • Could these traits be inherited?
  • How are traits passed from generation to
    generation?

2
The Central Dogma of Molecular Biology
  • Genes code ? enzymes ? perform functions in the
    cell that results in a phenotype
  • DNA ? RNA ? Protein

Transcription
Translation
3
10.1 Experiments showed that DNA is the genetic
material
  • Biologists had to find out the chemical nature of
    genes.
  • Griffith Transformation
  • Factors in heat-treated harmful bacteria can be
    transmitted to harmless bacteria that dont cause
    disease
  • Hershey-Chase
  • Offered supporting evidence that genes are
    composed of DNA
  • Showed that radioactive tagged DNA entered
    bacterial cells but radioactive tagged protein
    did not. Therefore genetic information is located
    in the DNA

4
DNA and RNA are polymers ofNucleotides
  • DNA Deoxyribonucleic Acid
  • Found in the nucleus
  • Three subunits
  • Deoxyribose (5 carbon sugar)
  • Phosphate
  • Nitrogen Base (can be 1 of 4)
  • Guanine
  • Cytosine
  • Adenine
  • Thymine

5
G pairs with C T pairs with A
Sugar-Phosphate Backbone
Nitrogenous Bases
6
Purines and Pyrimidines
Purines Have two rings
Adenine Guanine
Pyrimidines Have one ring
Thymine Cytosine
7
DNA is a double-stranded helix
  • Chargaffs Rules
  • Determined that the percent of guanine (G) and
    cytosine (C) are nearly equal in any sample of
    DNA the same was so for thymine (T) and adenine
    (A).
  • X-Ray Evidence
  • Rosalind Franklin took X-ray images of the DNA
    molecule that helped to develop the model for DNA
  • The Double Helix
  • Francis Crick and James Watson developed the
    double helix model of DNA

8
DNA is a double-stranded helix
  • A double helix looks like a spiral staircase.
  • Hydrogen bonds hold the two strands of DNA
    together
  • The As on one strand hydrogen bond to the Ts on
    the other, likewise for Gs and Cs
  • Base pairing explains why the percentage As is
    the same as the percentage of Ts

9
The shape of DNA is important because
  • Our DNA makes up 1 of our body weight, so a 150
    lb. person would have 1.5 lbs. of DNA.
  • In one cell 3 meters of DNA.
  • If you typed out your entire DNA sequence in
    Times 12pt font you would fill enough paper to
    reach the top of the Washington Monument in D.C.

10
DNA Replication
Video
  • It has not escaped our notice that the specific
    pairing we have postulated immediately suggests a
    possible copying mechanism for the genetic
    material Watson and Crick
  • The semi conservative model when a double helix
    replicates, each of the two daughter molecules
    will have one old strand (parental or template)
    and one new strand.

11
DNA Replication
Video
  • Step 1 Double helix unzips
  • Replication begins at origins of replication
  • Helicase unzipping enzyme
  • H-bonds break
  • Replication fork the point at which the two
    strands split
  • Step 2 Each original strand becomes a template
    strand (white)
  • Complementary bases fill in from the 5 end to
    the 3 end (opposite directions)
  • DNA polymerase building enzyme adds new bases
  • Step 3 Proofreading by DNA polymerase

12
DNA Replication
Enzyme (Helicase) Unzips
T A A G C
A T T C G
T A A G C
New Strands
T A A G C
Enzyme (DNA Polymerase) fills in new nucleotide
bases
13
The molecular basis for traits
  • An organisms genotype is its genetic make-up
  • A phenotype is the organisms specific trait.
  • For example the gene OCA2 causes the albino
    phenotype
  • The DNA specifies traits by providing the
    instructions on how to make protein.

14
The Chain of Command In the Cell
  • DNA ? RNA ? Protein
  • Genes code ? enzymes ? perform functions in the
    cell that results in a phenotype

Transcription
Translation
15
The one gene one enzyme hypothesis
  • Beadle and Tatum determined that mutant mold
    strains were defective in a single gene for each
    type of mutant
  • Their hypothesis that there is one gene for every
    enzyme was correct except it wasnt just for
    enzymes it was discovered that there is one gene
    for every protein. Further, scientists discovered
    that there are some proteins made of several
    polypeptides so again they changed the hypothesis
    to one gene one polypeptide.

16
RNA Structure
  • RNA Ribonucleic Acid
  • Single stranded!
  • Can leave the nucleus
  • Monomers made of
  • Ribose (5 carbon sugar)
  • Phosphate
  • Nitrogen Base (1 of 4)
  • Guanine
  • Cytosine
  • Adenine
  • Uracil (Instead of Thymine)

17
Three Kinds of RNA
  • Messenger RNA (mRNA)
  • conveys genetic information from the DNA in the
    nucleus to the rest of the cell
  • Ribosomal RNA (rRNA)
  • structural, part of ribosome
  • Transfer RNA (tRNA)
  • carries amino acids to site of protein synthesis,
    it is a material transporter (not for information)

18
Genetic information written in codons is
translated into amino acid sequences
  • RNA is a complementary copy of a DNA template
    strand instead of As pairing with Ts such as
    in DNA replication, the As in DNA pair with Us
    in RNA.
  • The mRNA is then decoded into protein through a
    process called translation.
  • Codons are groups of three nucleotide bases
  • Each codon on mRNA codes for a specific amino
    acid.

19
Transcription and Translation of Codons
20
Transcription
  • RNA polymerase creates the RNA sequence from the
    template DNA in the nucleus
  • Three Stages
  • Initiation RNA polymerase begins at the
    promoter sequence
  • Elongation RNA strand peals away from the DNA
    template
  • Termination RNA polymerase reaches the
    terminator sequence and detaches from the DNA

Animation
21
Transcription
DNA rezips
Enzyme (Helicase) Unzips
RNA Leaves to go to a ribosome
T A A G C
RNA Strand
U A A G C
Enzyme (RNA Polymerase) fills in new nucleotide
bases
Template Strand
22
CTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTCTGAAAGTGGAC
CTATCAGCAGGATGTGGGTGGGAGCAGATTAGAGAATAAAAGCAGACTGC
CTGAGCCAGCAGTGGCAACCCAATGGGGTCCCTTTCCATACTGTGGAAGC
TTCGTTCTTTCACTCTTTGCAATAAATCTTGCTATTGCTCACTCTTTGGG
TCCACACTGCCTTTATGAGCTGTGACACTCACCGCAAAGGTCTGCAGCTT
CACTCCTGAGCCAGTGAGACCACAACCCCACCAGAAAGAAGAAACTCAGA
ACACATCTGAACATCAGAAGAAACAAACTCCGGACGCGCCACCTTTAAGA
ACTGTAACACTCACCGCGAGGTTCCGCGTCTTCATTCTTGAAGTCAGTGA
ACCAAGAACCCACCAATTCCAGACACACTAGGACCCTGAGACAACCCCTA
GAAGAGCACCTGGTTGATAACCCAGTTCCCATCTGGGATTTAGGGGACCT
GGACAGCCCGGAAAATGAGCTCCTCATCTCTAACCCAGTTCCCCTGTGGG
GATTTAGGGGACCAGGGACAGCCCGTTGCATGAGCCCCTGGACTCTAACC
CAGTTCCCTTCTGGAATTTAGGGGCCCTGGGACAGCCCTGTACATGAGCT
CCTGGTCTGTAACACATTCCCCTGTGGGGATTTAGGGACTTGGGCCTTCT
GTCTTTGGGATCTACTCTCTATGGGCCACACAGATATGTCTTCCAACTTC
CCTACACAGGGGGGACTTCAAAGAGTGCCTTGAGCTGATCTGGTGATTGC
TTTTTTGTACTGTTATTTATCTTATTCTTTTCATTGTGAGGTACTGATGC
AAACACTTTGTACGAAAAGGTCTTTCTCATCTCGGGAGTCCCCGTCTATT
TGTCCCGGTCCCTGTTAACCCAGTCCCCGACAGGAGCCCCTTCTGCACCT
TGAGCTCTCACCACTCACCGTCCATCCAGCCCCAGCTCTGCCTGCAACCC
ACCCATCCCTGGGACTCGGGCCTCCCCTCTCTAGTGGTCTGGTCATCAGG
CCAGGGGCACGTGGAAGAAGCTATCGTGGCAAAGGGAGCAGTCATATCCC
CAAAATCTGTGGTTGGTTTACCACCACCATGGAAACCCCAGGGTGGGACT
CTAGTTTCAGGTTGGAGCTGAGCCCTGTCGGGAATGAGCTTTCCCCAGCT
ATGGCTTCTTGGGGCCCCTGTGCCCTGAGCTGTGTCTCCCAGCATCGGGT
CCCCACCATGCATATGGCCCACTCAGGCACAGTGCCGCGATGGCTGCATG
CGTGAGGGGGGCCTGGGCCCAGGGCTGGGAGTCCTTTGTGTCTCATGGCC
ATGATTGTCCTTCCGAGTATGATATGGTGGCCAATTTCTTTTATTCTGTC
GTTCAGAGTGAGTAAATGATGTAGAGTTCATGCAGAAAAAAATACAACAA
AAACCAAGGGAACATAGAATTGGAAAACGCGTCACAGCAATGAGTTAAAT
AGGTAACAAATTTCATCATTTGAAGAAAGACTTAGAGTGCCAAAAGTGCC
TCTTAAGTCTCCTTTAAAAAGTAGCAAAATTCATCCCTGAAGAAGCATCT
TGGCCTTTTTCATGTACTCAGAGTGCTGGTGAAGAACAAAGATTGCTGAA
ACATTATGTACCTAACAGCGTTACAGGGTGTAGATAACACACTGGAAAAC
CTGGTCGTTACAGTGGACATATTCCAGGAAGTCCTTGCCTGAGGTTTTCC
AAGTTATGGAATTGCTTGAGATTGGAAGAGGCGATGGAGGGTACAACTGT
AATGCCCAACCTCATTTTTGCTAACCCTGTTTTTAGACTCTCCCTTTCCT
TCAATCACCTAGCCTTCTTTCCACCTGAAAGGACTCTCCCTTAACTGAGA
GAACCGGACAGACTCCATCTTGGCTCTTTCACTGGCAGCCCCTTCCTCAA
AGACTTAACTCGTGCAAGCTGACTCCCAGGACATCCGAGAATGCAATTAA
CTGACAACCTACTGTGGCGAGCTACATCCGCAGTCCCCAGGAATTCGTCC
GATTGATAACGCCCAATTACCCGCGTCTATCACCTTGTAATAGTCTTAAA
GCACCTGCACCTGGAACTGTTTACTTTCCTGTAACCATTTATCCTTTTAA
CATTTTGCCTGATTTACTTATGTAAAATTCTTTTAACTAGACCGCCACTC
CCCTTTCTAAACAAAAGTATAAAAGAAAATCTAGCCCCTTCTTTGGGACT
GAGACAATTTTGAGGTTAACGCAGGGTGCCTGTAATCCTAAGGGAGGAGA
CCGCCACTTCTGCTGCCCTTCCCTTCCCCACACCCCCTTCTCTAGTTTAT
GAAACAGGGAAAAAGGGAGAAAGCAAAAAGATAAAAAAAACAGAAGTAAG
ATAAATAGCTAGACGACCTTGGCAGCACCACCCGGCACTGGTGGTTAAAA
TAATAATAATAATAATATTAACCCCTGACCTAAACTACTTGTGTTATCTG
TAAATTCCAGACACTGTATGAGGAAGCCCTGCAAAACTTTCTGTTCTGTT
ATCTGATGCGTGTAGCCCCCAGTCACGTTCCGATGCTTGCTCGATCTATC
ACGACCCTTTCAAGTGAACCCCTTAGAGTCGTAAACCCTTAAAAGGGCCA
GGAATTTCGTTTTCGGGGAGCTCGGCTCTTCAGGCCCAAGTAAACCTGCC
GTATCTCACCTGAGACCAACCCCCAACTACAAAACTCAACCTGGAATTTT
CCCAGGACCAAACCCATCTATATTCTGTAACCCGAAACCTCAAAGCCTAA
CCCTAACCCTAACCCCTACAGTTGAGGTCCCCCCGCCCCTGTGGTTCCAG
CTCAAGACAACCTGCCCCTCCGTGGGTTTGCAGGCCCTCTGGTGGGGGTG
GGAGCTGGGGGCCACATACAGCTCTCTGAGCTTAAGCCATTTTCTTCCTT
CATTCCTTCCTTCCTCCCTCCCTTCCCTTCCTTCCTCCCTCCCTCCCTCC
TTCCCTCCCTCCCTTTTTTTTTTCAGGGTCTTGCTCTGTCACCCAGGCTG
GAGTGCAGTGGCATGATCACAGCTGACTGCAGCCTCGGACTCCCAGGCTC
AAGTTATCTTCCCTCCTCAGCCTCCAGAGTAGGTGGGACTACAGGAGTGT
GCCATCGCACCCAGCGAATTTCTTAATTTTTATTTTGTAGAGATGAGGCC
TCTCGATATTGTCCAGGCTTGGAAGTAGTTCTTGAAATTCAAGAGGATCT
TGAAGTTCTGACCTCCTGTCAATATCCCTTCCCCTCACCTTGACCCTCCC
ATTCTGCCCCACCTGTCAGGATCACAAGGACCCCCAGATCAGCAGATGGG
AACCGGACCAAAAAGAGAAATAGTGCTGTCCCGCCCATAAGTACCACCCC
CAGACTCCCTGCTCCACCCTCTGGACCACAGGGAGGCCCCATGCTCCATC
CCTGAAAACCACCCCCAGACCCCCTGCTCCTCCCCACGGGACCGCCCCCA
GATCCACTGTTCCTGTCCTCCGGACCACACCGGACAGCTCCTTCCCTCGG
CGCCATCCCCAGACCCCAGCTCCTCCCCTCAGGATCATCCCCAGACCCCC
GCTCCTCCCATCAGGACCGCCCCCAGAACCCCCTGCTCCTCCCCACAGGA
CCACCCCCAGACCCCCGCTCCTCCCCTAAGGACCACCCACAGACCCCCAC
GCTTCCCCTCGGGACCACCCCCAGACCCCCGCTCCTCCCCTCAGGACCAC
CCCCAGATCCACTGTTCCTGTCCTCCGGACCACACCAGACAGCTCCTTCC
CTCGGCGCCATCCCCAGACCCCCACGCTTCCCCTCGGGACCACCCCCAGA
CCCCCGCTCCTGCCCTCGGGACCACGCCCAGACCCCCTGCTCCTCCCCAC
GAAACCACGCCCAGTAACCCCCCTCTTCTCCCCTCAGGACCACCCCCAGA
CCCCCGCTCCTCCCCTGGGAACCACCCCCAGACCCCCTGCTCCTCCCCAC
GAAACCACCCCCAGACTCCCTGCTCCTGTCCTCCGGACCACGCGACTGCT
CCTTCCCTCAGCGCCACCCCCAGACTGCCGCTCCTCCTGTCGGGACCCCC
TGAGGCTTTCTCCACCCGGAGTGCGGGGTAGGGAGCAGACGGAGAGTGAC
GGAGGGTGACGGAGAGTGACGAAAGTAGACGATGTCTGACGGAGAAGAGC
CGAGCGGAGCTGAAGGGCGGCGGAGAGTGACGGAAAGTGGCGAGAATTGA
CGGAAAGTGACGGGGACTGACGGACAGTGACGAAGAGTCACGAAATTTAT
CAGAGGGCGACAAAGAGGAAAGCGAAATGGTGAGATGCAGCCGGCCGAGC
CTAATCGGAGATGACGGAAAGTGACGGAGAGGAACGAGGAGTAAAGAGGG
GTGACGAAAAGAGCCGAAGCTGGTGGAGGCGAAGAACTGAGTGAGGGAAG
ATAGCCGAGATTAGCGGGTGGGCTGCAGCCGGGGCAGTCGCCCGAATGGG
CGGGACCCCACGGAGTTAGCGAGAGGATGCGAACAGCGGCCAGCCGGGCA
GCACGCGAGCGAGGGAGGGCGTGGAGGGCCGTGGGTCCGCCTGCACTGAG
GCAGGCATGCGTGGCACCGAGGTGACCCGGGTGGGAGGTGCACCGCCGCC
CCCTGGCAGTCTCTCCGCGGAGCCCAAGCCCGTCTTCTCCGCCCCTTTGC
AGACCTCGGCGCCCAGCCTGGCCCCTGACGCCCACCCGCGGCCCCACCCA
GCGCCCGGGCCCACGAGGCCGAGGAGCGGCGGAGACTAACGGCCCCTGGA
CCCCAGGCAGCACATGGCCCAGAGCATCCCAGCCCAGTGGAGGGCGGCAC
ATGGCGGGAGGGCGGGAGTCCGTGTCCACTCATGGCCGGGGAGGGGAGGG
CAAGTTCTGGTGGCTGGGGAGGCCTAGAGCATCACAGCCCAGTGGAGGGC
TGCACATGGCAGGGGAGGGGAGAGCAAGAGTGTGCGGGCGAGGGAGGAGA
GGGCAAGACTGCGTGTCCGCTCCAGTCTCTCTTCCTCATCTTATAAAGCC
ACGAGTCCCATGACTGGGGACCCAACCTAATAACATTATCTAATCCTAAT
TGCCTCCCAAAGGCCATATCTCCAATCAGGACATGAATTCGGGGATTAAA
TTGCCAACACATGGCTGGGCGCGATGGCTTGTGCTTTTTTTTTTTTTTTT
TTTGAGACGGAGTCTCGCTCTGTCGCCCAGGCTGGAGTGCAGTGGCGCTA
TCTCGGCTCACTGCAAGCTCTGCCTCCCGGGTTCACGCCATTCTCCTGCC
TCAGCCTCCTGAGTAGCTGGGACTACAGGCGCCCGCCACCACGCCCAGGT
AATTTTTTTTTTTTTTTTTTTGTATTTCTTTGTAGAGACGGGGTTTCACC
ATGTTAGCCAGGATGGTCTCGATCTCCTGACCTCGTGATCCACCCATCTC
GGTCTCCCAAAGTGCTAGGATTGCAGGCCTGAGCCACCGCACCCAGCTGC
CTTGTGCTTTTAATCCCAGCACTTTCAGAGGCCAAGGCAGGCGATCACCT
GAGGTCAGGAGTTCAAGACCAGCCTGGCCAACATGGTGAAACCCCATCTC
TAATACAAATACAAAAAAAAAACAAAAAACGTTAGCCAGGAATGAGGCCC
GGTGCTTGTAATCCTAAGGAAGGAGACCACCACTCCTCCTGCTGCCCTTC
CCTTCCCCACACCGCTTCCTTAGTTTATAAAACAGGGAAAAAGGGAGAAA
GCAAAAAGCTTAAAAAAAAAAAAAAAAAAACAGAAGTAAGATAAATAGCT
AGATGATCTTGGCAGCACCACCCGACCCTGGTGGTTAAAATAATAATAAT
AATAATATTAACCCCTGACCTAAACTACTTGTGTTATCTGTAAATTCCAG
ACACTGTATGAGGAAGCCCTGCAAAACTTTCTGTTCTGTTATCTGATGCG
TGTAGCCCCCAGTCACGTTCCCCATGCTTCCTCGATCTATCACAACCCTT
TCACGTAAACCCCTTAGAGTTGTAAACCCTTAAAAGGGCCAGGAATTTCG
TTTTCGGGGAGCTTGGCTCTTCAGGCGCAAGTGTGCCGATGCTCCTGGCA
GAGTAAAGCCCTTCCTTCTTTAACCCAGTGTCTGAGGAATTTTGTCTGCG
GCTTGTCCTGCCACAATGCCAGCTACCAGGAGGCTGAGGTGTGAGAATCG
CTCGAACCTGGGAGGCAGAGGTTGCAGCGAGCCGAGATCCCACGATTGCA
CTCCAGCCTGGGTGATAG
This DNA sequence will make a protein, however
not all of it will. Some of it is nonsense and
some of it gives information about when the
protein should be made where it should be sent,
etc.
23
Post Transcriptional RNA Modification
  • mRNA is edited before it makes protein
  • Introns (garbage)
  • Exons (the expressed genes)
  • mRNA also sometimes gets caps and tails before
    leaving the nucleus
  • Protect the RNA
  • Help it bind to a ribosome

24
The Genetic Code
  • Within the DNA is a code to make proteins
  • The genetic code is the set of rules that
    determines which codon codes for each amino acid
  • Redundancy but no Ambiguity
  • Start codon AUG
  • Find the stop codons

25
(No Transcript)
26
A Proteins Shape Determines its Function
  • Most enzymes are globular with a place the shape
    of the substrate where the substrate binds
    (active site).
  • Structural proteins (hair and tendons) are long
    and thin.

27
A Proteins Shape Depends on Four Levels of
Structure
  • Primary Structure the sequence of amino acids
  • Secondary Structure the protein folds into
    local patterns.
  • Alpha helix
  • Beta sheet
  • Tertiary Structure the overall,
    three-dimensional shape of the protein.
  • Quaternary Structure the combination of peptide
    chains (sub-units) that form the entire protein.

28
(No Transcript)
29
Translation
Firefly Movie
  • Ribosomes read mRNA and assemble polypeptides
  • mRNA is the message that comes directly from DNA
    (pink)
  • tRNA brings amino acids and matches them with the
    correct codon on mRNA (green)
  • tRNAs anti-codon is complementary to the mRNAs
    codon
  • tRNA enters the ribosome and drops off an amino
    acid (purple)
  • Amino acid binds with the growing polypeptide

30
Translation
  • Initiation Translation begins at an AUG (start
    codon) the tRNA binds with the anti-codon UAC
  • Elongation Amino acids are added to the
    polypeptide chain until a stop codon is read
  • Peptide bonds are formed between each pair of
    amino acids
  • Termination a stop codon is read by a tRNA
    carring no amino acid

31
Translation
Translation Animation
32
Gene Regulation
  • Not all genes are expressed in every cell
  • Not all genes are expressed at the same time.
  • An operon is a group of genes that operate
    together
  • A skin cell expresses different genes than a
    nerve cell

33
Gene Regulation
34
Mutations change the meaning of genes
  • A mutation is any change in the nucleotide
    sequence
  • Two types
  • Point mutations when one base is substituted
    for another
  • Frameshift mutations when a base is added or
    deleted (the entire reading frame is changed)

35
  • Point mutations (Substitutions)
  • Original The fat cat ate the wee rat.
  • Point Mutation The fat hat ate the wee rat.
  • Frameshift mutations (Insertion, Deletion)
  • Original The fat cat ate the wee rat.
  • Frame Shift The fat caa tet hew eer at.

Deletion
Substitution
Insertion
36
What causes mutations?
  • Spontaneous mistake (natural)
  • Mutagens a physical or chemical agent
  • Physical
  • Radiation
  • Chemical
  • Nicotine
  • Agent-Orange
  • Benzene
  • Bromine

37
What do mutations cause?
  • Diversity!
  • Genetic Disease
  • Sickle cell anemia
  • Cystic fibrosis
  • Huntingtons disease
  • Cancer
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