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Title: DNA-The code of life


1
DNA-The code of life
  • Why dont we all look alike?

2
WARM-UP 7
3
Why do we Study DNA?
  1. Disease
  2. Better vegetable, fruit, and animals.
  3. Crime
  4. History of life

4
DNA Facts
  • One chromosome has 50 - 250
  • million base pairs.
  • DNA is found in the mitochondria.
  • mDNA is only found in the egg. Sperm
  • has no mitochondria so mDNA is passed
  • to offspring from the mother.
  • One sequence of DNA is a genome or
  • gene.
  • Unwind all our DNA, it will stretch from the moon
  • and back 6000X.

5
http//public.ornl.gov/hgmis/gallery/
6
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7
  • Gene segment of DNA on your chromosomes that
    determines your traits.
  • Trait characteristics about you. It can be a
    part or a behavior. You inherited your traits
    from your parents.
  • What is the human genome?

8
Genetic material of cells
  • GENES units of genetic material that CODES FOR
    A SPECIFIC TRAIT
  • Called NUCLEIC ACIDS
  • DNA is made up of repeating monomers called
    NUCLEOTIDES

9
DNA(Deoxyribonucleic Acid)
10
A HISTORY OF DNA
  • Discovery of the DNA double helix
  • A. Frederick Griffith Discovers that a factor
    in diseased bacteria can transform harmless
    bacteria into deadly bacteria (1928)
  • B. Rosalind Franklin - X-ray photo of DNA.
  • (1952)
  • C. Watson and Crick - described the DNA
    molecule from Franklins X-ray.
  • (1953)

11
Discovery of DNA
Invented X-ray diffraction photography. Photo
used to determine the shape of DNA is spiral.
Rosalind Franklin -
12
DISCOVERY OF DNA
James Watson and Francis Crick used the
information from Franklin and other scientists to
build a 3-D model of DNA.
Won the Nobel Piece Prize in Chemistry in 1961.
13
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14
Watson Crick proposed
  • DNA had specific pairing between the nitrogen
    bases
  • ADENINE THYMINE
  • CYTOSINE - GUANINE
  • DNA was made of 2 long stands of nucleotides
    arranged in a specific way called the
    Complementary Rule

15
DNA
DNA stands for
Deoxyribonucleic acid
Functions of DNA 1. Carries the codes to make
proteins.
  1. Carries the genetic material that is passed on
    from the parents to the offspring.

16
STRUCTURE OF DNA
These three parts form the basic unit of DNA
called the NUCLEOTIDE.
phosphate
Nitrogen base Can be A, T, C or G
Sugar (deoxyribose)
17
STRUCTURE OF DNA
Side Pieces(The Rope Part)
Are alternating units of a 5 carbon sugar and a
phosphate group. These go down both sides of the
molecule
phosphate
Sugar (called deoxyribose)
18
STRUCTURE OF DNA
Nitrogen Bases (Steps of the ladder) -
  • Adenine - A
  • Thymine T
  • Cytocine C
  • Guanine - G


The bases are connected to the sugar only !!!!!
19
DNA Nucleotide

20
phosphate
adenine
sugar
thymine
cytocine
guanine
21
How are the nucleotides held together?
  • Nucleotides are held together by covalent bonds
    between the sugar of one nucleotide and the
    phosphate of the next.

22
DNA
23
DNA Double Helix

24
Nitrogenous Bases
  • PURINES
  • 1. Adenine (A)
  • 2. Guanine (G)
  • PYRIMIDINES
  • 3. Thymine (T)
  • 4. Cytosine (C)

25
BASE-PAIRINGS
  • 2 Bonds

3 bonds
26
STRUCTURE OF DNA
One complete turn of the double helix is 10 base
pairs or 10 steps on the ladder
27
DNA Double Helix

28
Chargaffs Rule
  • Adenine must pair with Thymine
  • Guanine must pair with Cytosine
  • Their amounts in a given DNA molecule will be
    about the same.

29
Chargaffs Rule
  • Chargaff discovered that the percentage of A and
    T were equal. The same for C and G. This
    observation became Chargaffs rule. This is
    always the same no matter what organisms.

30
Genetic Diversity
  • Different arrangements of NUCLEOTIDES in a
    nucleic acid (DNA) provides the key to DIVERSITY
    among living organisms.

31
The Code of Life
  • The code of the chromosome is the SPECIFIC
    ORDER that bases occur.
  • A T C G T A T G C G G

32
DNA is wrapped tightly around histones and coiled
tightly to form chromosomes
See p. 297
33
How does DNA copy itself?
Purpose DNA copies itself to ensure that each
new cell that is produced in gets the correct
number of chromosomes and receives an EXACT copy
of the DNA molecule. Replication must occur
before cell division.
34
  • This is called DNA REPLICATION.
  • The DNA molecule serves as its own pattern or
    template so as an exact copy can be made.

35
Watson and Crick
  • The model that Watson and Crick where the
    nitrogen bases pair suggested a mechanism for
    DNA to replicate.

36
Messelson and Stahl
  • They proved that DNA is semiconservative by
    attaching radioactive material to DNA. As the
    cell divided, they observed the new DNA in each
    cell and saw that it contained half of the old.
  • Semiconservative contains half of the old strand
    when DNA is replicated.

37
STEPS OF DNA REPLICATION
1. Helicase begin to unzip the double helix at
many different places. The hydrogen bonds
between the bases are broken. Occurs in two
different directions.
2. Free floating in the cytoplasm nucleotides
pair with the bases on the template. DNA
polyermase bonds together the nucleotides.
Small segments are bonded together.
38
  • Two identical strands of DNA result. The DNA
    will twist back together. DNA is called
    SEMICONSERVATIVE because it uses an old strand to
    make a new one.
  • This results in 2 new identical DNA molecules.

39
DNA Replication Video http//www.youtube.com/watc
h?vzdDkiRw1PdUfeatureplayer_embedded
40
DNA Replication Fork
Point where DNA is split apart to replicate.
Forms a Y!
41
Role of Enzymes
  • 1. Helicase unzips the two DNA strands.
  • 2. DNA polymerase is the enzyme that joins
    individual nucleotides to produce a new strand of
    DNA. Proofreads DNA when finished!

42
DNA Replication in Prokaryotic Cells
  • 1. Proteins binds to starting point.
  • 2. Starts at a single point and proceeds in both
    directions.

43
Eukaryotic Replication
  • Since eukaryotic cells are so much bigger, the
    replication will start at dozens to hundreds of
    different places on the DNA.

44
DNA REPLICATION
What if there is a mistake?
There is always a chance that the wrong
nucleotide bonds to another. HOWEVER, DNA
polymerase is responsible for reading the bases
and recognizing and replacing damaged or wrong
nucleotides. This PROOFREADING allows for only
one (1) error in ONE BILLION nucleotides.
45
DNA Fingerprinting
  • When DNA is found at a crime, the DNA is
    replicated many times to make enough to test.
    Once they have fingerprinted it, they can compare
    to find suspect.
  • Video
  • http//www.bing.com/videos/search?qdnacrimescen
    eviewdetailmid684167203C024AD0C797684167203C02
    4AD0C797first21FORMLKVR22adltstrict

46
DNA Fingerprinting
47
Speed of DNA Replication
  • In the human cell, 50 nucleotides can be added
    every second. It would that several days for
    replication to occur if the DNA did not start at
    several spots on the DNA so that it is occurring
    in many places on the DNA strand.

48
Transciption Making of RNA
  • Transcription process of copying DNA to produce
    a complimentary strand of RNA.

49
Types of RNA
There are three (3) types RNA
1. Messenger RNA (mRNA) carries messages from
the DNA in the nucleus to the cytoplasm.
2. Transfer RNA (tRNA) 20 different kinds
which are only able to bond with one (1) specific
type of amino acid.
50
Types of RNA
  • 3. Ribosomal RNA (rRNA) major component (part)
    of the ribosomes

51
RNA TRANSCIPTION
Transcription the process by which DNA makes
RNA.
Steps in RNA Transcription
  1. A special enzyme tells DNA its time to make RNA.
  2. The enzyme tells the nucleotides to only bond
    with RNA nucleotides.
  3. The code letters for RNA are A, C, G and U.

52
RNA TRANSCIPTION
  • 4. Process occurs just like DNA replication
  • --When complete, only a single strand of RNA is
    formed UNLIKE DNAs double strand.
  • --All three types of RNA are formed this way.
  • --All leave the nucleus and travel out into the
    cytoplasm.

53
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54
Transcription Video
  • http//www.bing.com/videos/search?qtranscription
    viewdetailmidEE2661D88067BDEFF3E7EE2661D88067BD
    EFF3E7first0FORMLKVR8adltstrict

55
RNA TRANSLATION
Protein Synthesis the formation of a protein
using information coded on DNA and carried out by
RNA in the assembly of amino acids.
  • Proteins are
  • Amino acids in chains 20 kinds
  • Made of 10s or 100s or 1000s of amino acids
  • Must be arranged in a specific sequence for each
    type of protein
  • Function type of protein is determined by amino
    acid sequence
  • DNA makes RNA
  • RNA orders the amino acids

56
RNA TRANSLATION
Translation Process
  • mRNA goes to the ribosomes, tRNA
  • goes to the cytoplasm.
  • 2. tRNA picks up amino acids brings them
  • to the ribosome.
  • 3. mRNA tells tRNA in which sequence to
  • assemble the proteins.(mRNA is the template!)
  • 4. An amino acid chain is a protein.

57
RNA TRANSLATION
So WHAT??
RNA makes amino acid chains
DNA makes RNA
Amino acid chains make proteins
Proteins make cells
58
Go to gslc.genetics.utah.edu/units Translate
Transcribe a Protein and What is a Protein?
59
Translation
  • Groups of 3 nucleotides on the mRNA code for each
    amino acid to build a protein.
  • These groups of 3 are called CODONS
  • The tRNA brings the correct amino acid to the
    chain.
  • You will build your own proteins tomorrow with
    the mRNA that you made yesterday!

60
We have been told that DNA is the blueprint for
life, BUT what does that mean?
DNA holds the instructions that tell a cell how
to construct amino acid chains.
That is important because amino acid chains build
proteins.
Proteins build cells
AND
61
Steps to Protein Synthesis
  • 1. DNA replication make new DNA
  • 2. Transcription DNA message given to RNA
  • 3. Translation RNA is translated in amino acid
    chains(protein).

62
Prokaryotic - Protein synthesis
  • Location cytoplasm
  • At the same time.
  • Eukaryotic Protein synthesis

63
SO, HOW DOES AN AMINO ACID CHAIN GET BUILT?
Well, first we have to make something called RNA
RNA stands for ribonucleic acid
It differs from DNA in three ways
1. RNA is single stranded.
2. The sugar in RNA is called ribose.
  1. Uracil is one of the bases in RNA. There is NO
    thymine in RNA. This means A goes with U and G
    still goes with C.

64
DNA Replication
  • Replication coping of DNA
  • The DNA molecule produces 2 IDENTICAL new
    complementary strands following the rules of base
    pairing
  • A-T, G-C
  • Each strand of the original DNA serves as a
    template for the new strand

65
Semiconservative Model
  • Replication is called semiconservation because
    one strand of DNA is used to as a template to
    make the new DNA.

66
Steps of DNA Replication
  • 1.DNA unzips and the hydrogen bonds between the
    nitrogen bases pulled apart. The base pairs are
    separated and are left exposed. This occurs in
    two different directions. This occurs along
    hundreds of different places at a time.
  • .

67
Steps of Replication
  • 2. Free-floating nucleotides are paired up to the
    free nucleotides. DNA polymerase bond the
    nucleotides together.
  • 3.Two identical strands result. DNA polymerase
    checks for mistakes when complete.

68
DNA Replication
  • DNA has 80 million base pairs in a chromosomes.
    DNA is copied at about 50 base pairs per second.
    This would take a month if replication did not
    occur at hundreds of different places at once.

69
Replication Quiz
  • 1. Why is replication necessary?
  • 2. When does replication occur?
  • 3. Describe how replication works.
  • Use the complementary rule to
  • create the complementary strand

A---? G---? C---? T---? A---? G---? A---? G---? C-
--? A---? G---? T---?
70
Replication Quiz
  • 1. Why is replication necessary?
  • So both new cells will have the correct DNA
  • 2. When does replication occur?
  • During interphase (S phase).
  • 3. Describe how replication works.
  • Enzymes unzip DNA and complementary nucleotides
    join each original strand.
  • 4. Use the complementary rule to
  • create the complementary strand

A---T G---C C---G T---A A---T G---C A---T G---C C-
--G A---T G---C T---A
71
(1961) Watson Crick proposed
  • DNA controlled cell function by serving as a
    template for PROTEIN structure.
  • 3 Nucleotides a triplet or CODON
  • (which code for a specific AMINO ACID)
  • See p.303
  • AMINO ACIDS are the building blocks of proteins.

72
DNA Transcription
  • DNA can unzip itself and RNA nucleotides match
    up to the DNA strand.
  • Both DNA RNA are formed from NUCLEOTIDES and
    are called NUCLEIC acids.

See p.301
73
DNA Translation
  • The cell uses information from messenger RNA to
    produce proteins

See p.304-305 We will discuss details of this on
a later date
74
Transcription/Translation Quiz
  • Why is transcription necessary?
  • Describe transcription.
  • Why is translation necessary?
  • Describe translation.
  • What are the main differences between DNA and
    RNA.
  • Using the chart on page 303, identify the amino
    acids coded for by these codons
  • UGGCAGUGC

75
  • 1. Why is transcription necessary?
  • Transcription makes messenger RNA (MRNA) to
    carry the code for proteins out of the nucleus to
    the ribosomes in the cytoplasm.
  • 2. Describe transcription.
  • RNA polymerase binds to DNA, separates the
    strands, then uses one strand as a template to
    assemble MRNA.
  • 3. Why is translation necessary?
  • Translation assures that the right amino acids
    are joined together by peptides to form the
    correct protein.

76
  • 4. Describe translation.
  • The cell uses information from MRNA to produce
    proteins.
  • 5. What are the main differences between DNA and
    RNA.
  • DNA has deoxyribose, RNA has ribose DNA has 2
    strands, RNA has one strand DNA has thymine, RNA
    has uracil.
  • Using the chart on page 303, identify the amino
    acids coded for by these codons UGGCAGUGC
  • tryptophan-glutamine-cysteine

77
AMAZING DNA FACTS
  • DNA from a single human cell extends in a single
    thread for almost 2 meters long!!!
  • It contains information equal to some 600,000
    printed pages of 500 words each!!!
  • (a library of about 1,000 books)

78
LETS REVIEW DNALM p.44
  1. List the conclusions Griffith Avery, Hershey
    Chase drew from their experiments.
  2. Summarize the relationship between genes DNA.
  3. Describe the overall structure of the DNA
    molecule.
  4. What are the 4 kinds of bases?
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