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DNA / RNA

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Title: DNA / RNA


1
DNA / RNA
  • Chapter 08

2
DNA
  • Deoxyribonucleic acid (DNA) is a nucleic acid
    that contains the blueprint for making the
    proteins the cell needs.
  • DNA contains genes.
  • Genes are specific messages instructing the cell
    on how to construct a protein.

3
DNA
  • DNA is the chemical used to pass genetic
    information on to the next generation of
    organisms.
  • DNA controls the synthesis of proteins, which
    helps determine the characteristics of the
    organism and regulate the cells metabolism.

4
DNA
  • DNA contains the genetic instructions used in the
    development of all known living organisms and
    some viruses.
  • DNA molecules are used for long term storage of
    information.
  • DNA carries the instructions necessary to create
    RNA and proteins therefore, it is often compared
    to a blueprint.

5
DNA Structure
  • DNA is a nucleic acid.
  • Nucleic acids are large polymers of nucleotides.

6
DNA Structure
  • DNA consists of two long polymers of simple units
    known as nucleotides.
  • These two strands run in opposite directions to
    each other and are therefore known as
    anti-parallel.
  • The strands have backbones made of sugars with
    phosphate groups attached.

7
DNA Structure
  • Attached to each sugar is one of four types of
    molecules called bases.
  • Information is encoded in the sequence of these
    four bases along the backbone.
  • The information is read using the genetic code.

8
DNA Structure
  • The genetic code specifies the sequence of amino
    acids within proteins.
  • The code is read by copying stretches of DNA into
    RNA (A process known as transcription).

9
DNA Structure
  • A nucleotide consists of a sugar molecule, a
    phosphate group, and a nitrogenous base.
  • There are four different nitrogenous bases in DNA

10
DNA Structure
  • Adenine (A), guanine (G), cytosine (C), and
    thymine (T).
  • The DNA nucleotides can combine into a long
    linear DNA molecule that can pair with another
    linear DNA molecule.

11
DNA Structure
  • The two paired strands of DNA form a double helix
    with sugars and phosphates on the outside and the
    nitrogenous bases on the inside.
  • The nucleotides form hydrogen bonds with one
    another, which helps to stabilize the helical
    structure.

12
DNA Structure
  • Adenine pairs with Thymine (A-T).
  • Guanine pairs with Cytosine (G-C).

13
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14
Nitrogenous Bases
  • The nucleotide bases are nitrogenous bases that
    are involved in pairing in DNA and RNA. This is
    known as base pairing.
  • In genetics they are simply called bases.
  • Adenine, Guanine, Cytosine, and Thymine are DNA
    bases.
  • Adenine, Guanine, Cytosine, and Uracil are RNA
    bases.

15
Adenine
16
Guanine
17
Thymine
18
Cytosine
19
Uracil
20
Chromosomes
  • Within cells, DNA is organized into structures
    called chromosomes.

21
Chromosomes
  • The chromosomes are duplicated before the cell
    divides, a process known as DNA replication.
  • Within the chromosomes, chromatin proteins such
    as histones compact and organize DNA. The
    chromatins help determine which parts of the DNA
    are transcribed.

22
Eukaryotes Vs. Prokaryotes
  • Eukaryotic organisms (animals, plants, fungi, and
    protists) store their DNA inside the cell
    nucleus.
  • Prokaryotic organisms (bacteria and archae) have
    no nucleus therefore, the DNA is found in the
    cytoplasm.

23
DNA Replication
  • When a cell grows and divides, two new cells
    result.
  • DNA replication is the process by which a cell
    makes another copy of its DNA.
  • Base pairing rules and many enzymes make
    replication possible.

24
DNA Replication
  • DNA replication is the process of copying a
    double-stranded DNA molecule to form two
    double-stranded molecules.

25
DNA Replication
  • Each DNA strand holds the same genetic
    information therefore, both strands can serve as
    a template for the reproduction of the
    complementary strand.
  • The template strand is conserved in its entirety
    and the new strand is assembled from nucleotides.
    This is known as semiconservative replication.

26
DNA Replication
  • The resulting double-stranded DNA molecules are
    identical.
  • DNA replication must happen before cell division
    can occur.

27
DNA Replication
  • Helicases are enzymes that bind to the DNA and
    separate the two strands of DNA.
  • DNA polymerase incorporates DNA nucleotides into
    the new DNA strand. The nucleotides enter
    according to the base pairing rules.

28
DNA Replication
  • In prokaryotic cells, this replication process
    starts at only one place along the DNA molecule
    (origin of replication).
  • In eukaryotic cells, the replication starts at
    the same time along several different places of
    the DNA molecule.

29
DNA Replication
  • Two new identical, double-stranded DNA molecules
    are formed.
  • The new strands of DNA form on each side of the
    old DNA strands.

30
DNA Replication
  • The exposed nitrogenous bases of the original DNA
    serve as the pattern on which the new DNA is
    formed.
  • Two double helices are formed with identical
    nucleotide sequences.
  • A portion of the DNA polymerase molecule edits
    the newly created DNA molecule and makes
    corrections if needed.

31
DNA Replication
32
Repair of Genetic Information
  • If an error or damage occurs to the DNA helix on
    one strand, the pairing arrangement of
    nitrogenous bases on the other undamaged strand
    can be read.
  • This information is used to repair the damaged
    strand.

33
DNA Code
  • DNA stores information.
  • The order of the nitrogenous bases is the genetic
    information that codes for proteins.
  • The nucleotides are read in sets of three.
  • Each sequence of three nucleotides is a codeword
    for a single amino acid.
  • The information to code one protein can be
    thousands of nucleotides long.

34
RNA Structure And Function
  • Ribonucleic Acid (RNA) is important in protein
    production.
  • RNAs nucleotides contain a ribose sugar whereas
    DNAs nucleotides contain a deoxyribose sugar.
  • Ribose has an OH group and deoxyribose has an H
    group on the second carbon atom.

35
RNA Structure And Function
  • RNA contains the nitrogenous bases Uracil (U),
    guanine (G), cytosine (C), and adenine (A).
  • DNA is found in the cells nucleus, while RNA is
    made in the nucleus and then moves out into the
    cytoplasm of the cell.

36
RNA Structure And Function
  • DNA directs protein synthesis by using RNA.
  • RNA is made by enzymes that read the protein
    coding information in DNA.
  • RNA nucleotides pair with DNA nucleotides.
  • RNA contains Uracil instead of Thymine so adenine
    in DNA pairs with Uracil in RNA.

37
Nucleic Acid Base Pairing Rules
DNA pairs with DNA DNA pairs with RNA RNA pairs with RNA
A pairs with T A pairs with U A pairs with U
T pairs with A T pairs with A U pairs with A
G pairs with C G pairs with C G pairs with C
C pairs with G C pairs with G C pairs with G
38
Transcription
  • Transcription is the process of using DNA as a
    template to synthesize RNA.
  • The RNA polymerase enzyme reads the sequence of
    DNA nucleotides and follows the base pairing
    rules between DNA and RNA to build the new RNA
    molecule.

39
Transcription
  • The two strands of the double stranded DNA
    molecule are separated to expose the nitrogenous
    bases.
  • The DNAs nitrogenous bases are read and paired
    with the RNA nucleotides.
  • Only one strand of the DNA molecule is read (the
    coding strand). The other strand is referred to
    as the non-coding strand.

40
Transcription
  • Promoter sequences are specific sequences of DNA
    nucleotides that RNA polymerase uses to find a
    protein-coding region of DNA and to find out
    which strand of DNA is the coding strand.

41
Transcription
  • Termination sequences are DNA nucleotide
    sequences that indicate when RNA polymerase
    should finish making an RNA molecule.

42
3 Types of RNA
  • Messenger RNA (mRNA) carries the blueprint for
    making the necessary protein.
  • Transfer RNA (tRNA) reads mRNA and brings in
    the necessary amino acids.
  • Ribosomal RNA (rRNA) reads the mRNA and brings
    in the necessary amino acids.

43
Translation
  • Translation is the process of using information
    in RNA to direct protein synthesis.
  • mRNA is read in sets of three nucleotides called
    codons.

44
Translation
  • A codon is a set of three nucleotides that codes
    for a specific amino acid.
  • The ribosome is made up of proteins and ribosomal
    RNA (rRNA).
  • The ribsome holds the mRNA in place and reads
    its codons.

45
3 Phases of Translation
  • Initiation
  • Elongation
  • Termination

46
Initiation
  • The small ribosomal subunit binds to the mRNA and
    moves along until it reaches an AUG codon to
    signal the beginning of translation.
  • Transfer RNA (tRNA) carries amino acids to the
    mRNA complex.

47
Initiation
  • The anticodon portion of the tRNA interacts with
    the mRNA to match the correct amino acid to the
    codon in the mRNA nucleotide sequence.
  • The tRNA that binds to the AUG codon that signals
    the beginning of translation carries the amino
    acid methionine therefore, every protein begins
    with this amino acid.

48
Elongation
  • The ribosome functions as an assembly line.
  • New amino acids are carried by tRNA to the
    corresponding mRNA segment.
  • The anticodon on tRNA matches with the codon on
    mRNA.
  • The amino acid is then attached to the end of the
    chain and the protein becomes elongated.

49
Termination
  • The ribosome will continue to add new amino acids
    until a stop signal is reached on the mRNA
    molecule.
  • The stop codon can be either UAA, UAG, or UGA.

50
Termination
  • When these codons are encountered, a release
    factor enters the ribosome. The ribosomal
    subunits release mRNA.
  • The mRNA can then either be reused or broken down
    to stop protein production.

51
Translation
52
Nearly Universal Genetic Code
  • The code for making protein from DNA is the same
    for nearly all cells.
  • Bacteria, protists, plants, fungi, and animals
    all use DNA to store their genetic information.
  • They all transcribe information in DNA to RNA.
  • They all translate the RNA to synthesize protein
    using a ribosome.

53
Nearly Universal Genetic Code
  • Almost all use the same three nucleotide codons
    to code for the same amino acid.
  • In eukaryotic cells, transcription always occurs
    in the nucleu, and translation always occurs in
    the cytoplasm.

54
Nearly Universal Genetic Code
  • These similarities make it possible to use
    bacteria to synthesize human proteins (i.e.
    insulin).
  • Some viruses use RNA to store their genetic
    information (retroviruses). HIV is an example of
    this. Retroviruses use RNA to make DNA, which is
    then used to make proteins.

55
Gene Expression
  • Gene expression occurs when a cell transcribes
    and translates a gene.
  • Cells control which genes are used to make
    proteins.
  • The different cell types in the human body are
    due to which proteins the cell is producing.

56
Controlling Protein Quantity
  • An enzymes activity can be regulated by
    controlling how much of that enzyme is made.
  • The cell controls how much mRNA is available for
    translation, which in turn determines the
    quantity of the protein produced.

57
Controlling Protein Quantity
  • Enhancer and silencer sequences affect the
    ability of RNA polymerase to transcribe a
    specific protein.
  • Enhancer sequences increase protein synthesis by
    increasing transcription.
  • Silencer sequences decrease protein production by
    decreasing transcription.

58
RNA Degradation
  • Cells regulate gene expression by limiting the
    length of time that mRNA is available for
    translation.
  • Enzymes in the cell break down mRNA.

59
Mutations
  • A mutation is any change in the DNA sequence of
    an organism.
  • Errors during DNA replication can cause mutation.
  • External factors can cause mutation

60
Mutations
  • Radiation, carcinogens, drugs, viruses.
  • Not all mutations cause a change in the organism.
  • If the mutation occurs away from the
    protein-coding sequence of the DNA, it is
    unlikely to be harmful to the organism.

61
Silent Mutation
  • A silent mutation is a change that does not
    change the amino acids used to build a protein.

62
Nonsense Mutation
  • A nonsense mutation causes a ribosome to stop
    protein synthesis by introducing a stop codon too
    early.
  • This prevents the formation of functional
    proteins.

63
Missense Mutation
  • A missense mutation causes the wrong amino acid
    to be used in making a protein.
  • This will change the shape of the protein and
    affect its active sites.
  • This can cause an abnormally functioning protein.

64
Insertions And Deletions
  • Some mutations involve larger spans of DNA than a
    change in a single nucleotide.
  • An insertion mutation adds one or more
    nucleotides to the normals DNA sequence.

65
Insertions And Deletions
  • This can add amino acids to the protein and
    change its function.
  • A deletion mutation removes one or more
    nucleotides.
  • This can delete amino acids from the protein and
    change its function.
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