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Do Now 4. Write everything you know about DNA. Write something that you kind of know, or have heard, about DNA. Write something you would like to know, or think your about to learn, about DNA. DNA. Chapter 10. Essential Question:. How do we know DNA makes up our genetic material?.

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Do now 4

Do Now 4

  • Write everything you know about DNA.

  • Write something that you kind of know, or have heard, about DNA.

  • Write something you would like to know, or think your about to learn, about DNA.


Do now 4

DNA

Chapter 10


How do we know dna makes up our genetic material

Essential Question:

How do we know DNA makes up our genetic material?

  • Griffith: Pneumonia strains & Transformation

  • Oswald Avery: Process of elimination.

    • Used enzymes to destroy components of bacterial strains. Transformationoccurred in the absence of all macromolecules, exceptDNA.

  • Hershey & Chase: Bacteriophages

    • By using radioactiveisotopes, it was discovered that DNA is the genetic material of viruses.


Griffith

EQ: How do we know DNA makes up our genetic material?

Griffith

  • Transformation: One strain of bacteria was permanently genetically altered.


Oswald avery

EQ: How do we know DNA makes up our genetic material?

Oswald avery

  • I’m thinking of a number between 1 & 5.

  • 1

  • 2

  • 3

  • 4

  • 5

  • Proteins

  • Carbs

  • Lipids

  • DNA

  • Other molecues


Do now 4

EQ: How do we know DNA makes up our genetic material?

0

Head

DNA

Tail

Tail fiber


Do now 4

EQ: How do we know DNA makes up our genetic material?

0

Phage injects DNA.

Phage DNA directs host

cell to make more phage

DNA and protein parts.

New phages assemble.

Phage attaches

to bacterial cell.

Cell lyses and

releases new phages.


Dna replication animations

EQ: How do we know DNA makes up our genetic material?

DNA Replication animations

  • dna replication fork - http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#


Review

“Review”

  • What 3 experiments led us to know that DNA makes up genetic information?

  • What is the purpose of DNA?

  • What do you remember about the structure of chromosomes?


The components and structure of dna

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • What is the overall structure of the DNA molecule?


Dna is a type of nucleic acid

DNA is a type of Nucleic Acid

  • Nucleic acids are long, slightly acidic molecules originally identified in cell nuclei.

    • Nucleic acids are made up of nucleotides, linked together to form long chains.


The components and structure of dna1

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • The Components and Structure of DNA

    • DNA is made up of nucleotides.

      • A nucleotide is a monomer (single molecule) of nucleic acids made up of

        • A five-carbon sugar called deoxyribose

        • aphosphategroup

        • & one of fournitrogenousbases.


The components and structure of dna2

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • The nucleotides in a strand of DNA are joined by covalent bonds formed between their sugar and phosphate groups.

Covalent

bonds


The components and structure of dna3

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • There are four kinds of nitrogen bases in DNA:

  • adenine

  • guanine

  • cytosine

  • thymine


Do now 4

  • 1.) Adenines & Guanines belong to a class of nitrogenous base known as ________.

  • 2.) Cytosines and Thymines belong to a class of nitrogenous base known as ______.

Double Ring Structures

Single Ring Structures


The components and structure of dna4

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • The backbone of a DNA chain is formed by sugar and phosphate groups of each nucleotide.

  • The nucleotides can be joined together in any order.


Do now 5

Do Now 5

  • Summarize the roles of Griffith, Avery, & Hershey & Chase in determining that DNA contains our genetic material.

  • What did Chargaff, Franklin, & Watson & Crick contribute to understanding the structure of DNA.


Ec what led to the discovery of the structure of dna

EC: What led to the discovery of the structure of DNA?

  • EC: What led to the discovery of the structure of DNA?


The components and structure of dna5

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • Chargaff's Rules

    • Erwin Chargaff discovered that:

      • The percentages of guanine [G] and cytosine [C] bases are almost equal in any sample of DNA.

      • The percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA.


The components and structure of dna6

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • Chargaff's Rules

    • Erwin Chargaff discovered that:

      • For every guaninethere is a cytosine

        [G]=[C]

      • For every adeninethere is a thymine

        [A]=[T]


The components and structure of dna7

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

Franklin’s X-Ray Evidence 

  • In the 1950’s Rosalind Franklin used X-ray diffraction to get information about the structure of DNA.


Do now 4

EC: What led to the discovery of the structure of DNA?

  • X-ray diffraction revealed an X-shaped pattern showing that the strands in DNA are twisted around each other like the coils of a spring.

    • Suggested two strands in the structure.

    • Suggested that the nitrogenous bases are near the center of the DNA molecule.


The components and structure of dna8

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • The Double Helix 

    • Watson and Crick's model of DNA was a double helix, in which two strands were wound around each other like a twisted ladder.


Do now 4

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

  • 2 sugar-phosphate “backbones” make up the two sides of the twisting ladder.

  • The third component of the nucleotide, the nitrogenous bases, make up the rungs (steps) of the ladder.


The components and structure of dna9

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • In the double-helix model, the two strands of DNA are “antiparallel”—they run in opposite directions.

    • Enables the nitrogenousbases on both strands to come into contact at the center of the molecule.


Anti parallel strands

Anti-parallel strands

  • Nucleotides in DNA backbone are bonded from phosphate to sugar between 3 & 5 carbons

    • DNA molecule has “direction”

    • complementary strand runs in opposite direction

5

3

3

5


Do now 4

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

5’

3’

  • DNA Double Helix

5’

3’


The components and structure of dna10

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

The Components and Structure of DNA

  • Watson and Crick discovered that hydrogen bonds can form between certain nitrogenousbase pairs.

    • This principle is called base pairing.

    • Hydrogen Bonds hold the rungs of the latter together.


Do now 4

EC: What led to the discovery of the structure of DNA?

EQ: What is the overall structure of DNA?

  • Base pairing explained Chargaff’srule: why…

    [A] = [T] and [G] = [C].

    • For every adenine in a double-stranded DNA molecule, there had to be exactly one thymine. For each cytosine, there was one guanine.

3’

5’

5’

3’


Eq what is the overall structure of dna

Review: The Components and Structure of DNA

EQ: What is the overall structure of DNA?

  • DNA is made up of nucleotides that consist of a 5 carbon deoxyribose sugar, a phosphate group, and 1 of 4 nitrogenousbases

  • DNA is takes a double helix shape, like a twisted ladder. Two sugar-phosphate backbones, which are held together by covalentbonds make up the sides of the twisted ladder while nitrogenous bases, held together by hydrogen bonds make up the rungs, or connect in the center.

  • The strands of the double helix run antiparallel, which allows them to link up as exact opposites.

  • Nitrogenous bases form hydrogen bonds with their base pair A-T, C-G.


Do now 4

Review: The Components and Structure of DNA

EQ: What led to the discovery of the structure of DNA?

  • Chargoff determined that, in a double-stranded DNA molecule, adenine & thymine are present in equal proportions, as are guanine and cytosine.

  • Franklins X-Ray revealed the spiral structure of DNA.

  • Both contributed to Watson & Crick’s understanding of DNA’sdoublehelix and complementarybasepairing, which led to their double helix model of DNA.


Dna replication

Chapter 10.4

DNA replication


Double helix structure of dna

Double helix structure of DNA

“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”Watson & Crick


Base pairing in dna

Base pairing in DNA

  • Purines

    • adenine (A)

    • guanine (G)

  • Pyrimidines

    • thymine (T)

    • cytosine (C)

  • Pairing

    • A : T

      • 2 bonds

    • C : G

      • 3 bonds


Copying dna

Copying DNA

  • Replication of DNA

    • base pairing allows each strand to serve as a template for a new strand

    • new strand is 1/2 parent template & 1/2 new DNA


Dna replication1

DNA Replication

  • Large team of enzymes coordinates replication


Replication step 1 dna unwinds

Replication: step 1: DNA Unwinds

  • Unwind DNA

    • helicaseenzyme

      • unwinds part of DNA helix

      • stabilized by single-stranded binding proteins

helicase

single-stranded binding proteins

replication fork


Replication step 2 adding complementary nucleotides

Replication: step 2 Adding Complementary Nucleotides

  • Build daughter DNA strand

    • add new complementary bases

    • Uses DNA polymerase III

Where’s theENERGYfor the bonding!

DNA

Polymerase III


Energy of replication

Energy of Replication

Modified nucleotides

comewith their ownenergy!

Where does energy for bonding usually come from?

energy

YourememberATP!Are there other waysto get energyout of it?

energy

Are thereother energynucleotides?You bet!

And we are

left with anucleotide!

CTP

ATP

TTP

GTP

AMP

ADP

GMP

TMP

CMP

modified nucleotide


Energy of replication1

Energy of Replication

  • The nucleotides arrive as nucleosides

    • DNA bases with P–P–P

      • P-P-P = energy for bonding

    • DNA bases arrive with their own energysource for bonding

    • bonded by enzyme: DNA polymerase III

ATP

GTP

TTP

CTP


Replication

Replication

3

5

energy

DNA

Polymerase III

  • Adding bases

    • can only add nucleotides to 3 endof a growing DNA strand

      • need a “starter” nucleotide to bond to

    • strand only grows 53

DNA

Polymerase III

energy

DNA

Polymerase III

energy

DNA

Polymerase III

energy

3

5


Do now 4

ligase

5

3

5

3

need “primer” bases to add on to

energy

no energy to bond

energy

energy

energy

energy

energy

energy

3

5

3

5


Leading lagging strands

Okazaki

ligase

3

3

3

3

3

3

3

5

5

5

5

5

5

5

Leading & Lagging strands

Limits of DNA polymerase III

  • can only build onto 3 end of an existing DNA strand

Okazaki fragments

Lagging strand

growing

replication fork

Leading strand

Lagging strand

  • Okazaki fragments

  • joined by ligase

    • “spot welder” enzyme

DNA polymerase III

Leading strand

  • continuous synthesis


Lagging strands

Lagging Strands


Replication fork replication bubble

DNA polymerase III

3

3

3

3

3

3

3

3

3

3

3

growing

replication fork

growing

replication fork

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

Replication fork / Replication bubble

leading strand

lagging strand

leading strand

lagging strand

leading strand

lagging strand


Starting dna synthesis rna primers

3

3

3

3

3

3

DNA polymerase III

5

5

5

5

5

5

Starting DNA synthesis: RNA primers

Limits of DNA polymerase III

  • can only build onto 3 end of an existing DNA strand

growing

replication fork

primase

RNA

RNA primer

  • built by primase

  • serves as starter sequence for DNA polymerase III


Replacing rna primers with dna

ligase

3

3

3

3

5

5

5

5

Replacing RNA primers with DNA

DNA polymerase I

  • removes sections of RNA primer and replaces with DNA nucleotides

DNA polymerase I

growing

replication fork

RNA

But DNA polymerase I still can only build onto 3 end of an existing DNA strand


Replication fork

direction of replication

Replication fork

DNA polymerase III

lagging strand

DNA polymerase I

3’

primase

Okazaki fragments

5’

5’

ligase

SSB

3’

5’

3’

Helicase`

DNA polymerase III

5’

leading strand

3’

SSB = single-stranded binding proteins


Dna replication review

DNA REPLICATION review


Telomeres

DNA Replication

EQ: How can DNA replicate?

Telomeres

  • The tips of chromosomes are known as telomeres.

    • The ends of DNA molecules, located at the telomeres, are difficult to copy.

    • Over time, DNA may be lost from telomeres each time a chromosome is replicated.

    • What potential problem could this cause?


Telomeres1

DNA Replication

EQ: How can DNA replicate?

Telomeres

  • An enzyme called telomerase compensates for this problem by adding short, repeated DNA sequences to telomeres, lengthening the chromosomes slightly and making it less likely that important gene sequences will be lostfrom the telomeres during replication.


Chromosome erosion

3

3

3

3

5

5

5

5

Chromosome erosion

All DNA polymerases can only add to 3 end of an existing DNA strand

DNA polymerase I

growing

replication fork

DNA polymerase III

RNA

Loss of bases at 5 endsin every replication

  • chromosomes get shorter with each replication

  • limit to number of cell divisions?


Telomeres2

3

3

3

3

5

5

5

5

Telomeres

Repeating, non-coding sequences at the end of chromosomes = protective cap

  • limit to ~50 cell divisions

growing

replication fork

telomerase

Telomerase

  • enzyme extends telomeres

  • can add DNA bases at 5 end

  • different level of activity in different cells

    • high in stem cells & cancers -- Why?

TTAAGGG

TTAAGGG

TTAAGGG


Review lab today

Review/Lab today

  • Use your textbook and Notes.

  • Create a step by step comic strip showing DNA Replication.

  • Be sure to include each of the 12 terms listed to the side.

  • Be sure to plan your strip before you create it.

    • Figure out how many steps you will need.

    • Must include captions explaining each step.

    • May need more than one piece of paper.

    • Make the strip large enough to be clear.

  • Replication fork

  • Helicase

  • Binding Proteins

  • DNA Polymerase III

  • Ligase

  • Lagging Strand

  • Leading Strand

  • Okazaki fragments

  • Primase

  • DNA Polymerase I

  • Telomeres

  • Telomerase


How does dna replication differ in prokaryotic cells and eukaryotic cells

How does DNA replication differ in prokaryotic cells and eukaryotic cells?

  • Replication in most prokaryotic cells starts from a single point and proceeds in two directions until the entire chromosome is copied.

  • In eukaryotic cells, replication may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.


Prokaryotes

PROKARYOTES

  • DNA replication starts when regulatory proteins bind to a single starting point on the chromosome. This triggers the beginning of DNA replication.


Eukaryotic cells

Eukaryotic Cells

  • Eukaryotic cells can have up to 1000 times more DNA. Nearly all of the DNA of eukaryotic cells is found in the nucleus.

    • The two copies of DNA produced by replication remain closely associated until the cell enters prophase of mitosis, when the chromosomes condense.

      • What happens next?


Editing proofreading dna

Editing & proofreading DNA

  • 1000 bases/second = lots of typos!

  • DNA polymerase I

    • proofreads& corrects typos

    • repairsmismatchedbases

    • removesabnormalbases

      • repairs damage throughout life

    • reduces error rate from 1 in 10,000 to 1 in 100 million bases


Fast accurate

Fast & accurate!

  • It takes E. coli <1 hour to copy 5 million base pairs in its single chromosome

    • divide to form 2 identical daughter cells

  • Human cell copies its 6 billion bases & divide into daughter cells in only few hours

    • remarkably accurate

    • only ~1 error per 100 million bases

    • ~30 errors per cell cycle


Do now 4

Any Questions??


Chapter 10 dna review

Chapter 10 DnarEVIEW

  • Enzymes involved in replication:

    • Helicase

    • DNA Polymerase III

    • Ligase

    • DNA Polymerase I

    • Telomerase


Chapter 10 dna review1

Chapter 10 DnarEVIEW

  • Griffith: Pnemonia

  • Oswald Avery: Process of Elimination

  • Hershey & Chase: Bacteriophage, 32P & 35S

  • Erwin Chargaff

  • Rosalind Franklin

  • Watson & Crick

  • Structure


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