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DNA Biology and Technology

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Title: DNA Biology and Technology


1
  • DNA Biology and Technology

2
What must DNA do?
21.1 DNA and RNA structure and function
  • Replicate to be passed on to the next generation
  • Store information
  • Undergo mutations to provide genetic diversity

3
DNA structure A review
21.1 DNA and RNA structure and function
  • Double-stranded helix
  • Composed of repeating nucleotides (made of a
    pentose sugar, phosphate and a nitrogenous base)
  • Sugar and phosphate make up the backbone while
    the bases make up the rungs of the ladder
  • Bases have complementary pairing with cytosine
    (C) pairs with guanine (G) and adenine (A) pairs
    with thymine (T)

4
DNA structure
21.1 DNA and RNA structure and function
5
How does DNA replicate?
21.1 DNA and RNA structure and function
  • The two strands unwind by breaking the H bonds
  • Complementary nucleotides are added to each
    strand by DNA polymerase
  • Each new double-stranded helix is made of one new
    strand and one old strand (semiconservative
    replication)
  • The sequence of bases makes each individual unique

6
DNA replication
21.1 DNA and RNA structure and function
7
RNA structure and function
21.1 DNA and RNA structure and function
  • Single-stranded
  • Composed of repeating nucleotides
  • Sugar-phosphate backbone
  • Bases are A, C, G and uracil (U)
  • Three types of RNA
  • Ribosomal (rRNA) joins with proteins to form
    ribosomes
  • Messenger (mRNA) carries genetic information
    from DNA to the ribosomes
  • Transfer (tRNA) transfers amino acids to a
    ribosome where they are added to a forming
    protein

8
RNA structure
21.1 DNA and RNA structure and function
9
Comparing DNA and RNA
21.1 DNA and RNA structure and function
  • Similarities
  • Are nucleic acids
  • Are made of nucleotides
  • Have sugar-phosphate backbones
  • Are found in the nucleus
  • Differences
  • DNA is double stranded while RNA is single
    stranded
  • DNA has T while RNA has U
  • RNA is also found in the cytoplasm as well as the
    nucleus while DNA is not

10
Proteins A review
21.2 Gene expression
  • Composed of subunits of amino acids
  • Sequence of amino acids determines the shape of
    the protein
  • Synthesized at the ribosomes
  • Important for diverse functions in the body
    including hormones, enzymes and transport
  • Can denature causing a loss of function

11
Proteins A review of structure
21.2 Gene expression
12
2 steps of gene expression
21.2 Gene expression
  • Transcription DNA is read to make a mRNA in the
    nucleus of our cells
  • Translation Reading the mRNA to make a protein
    in the cytoplasm

13
Overview of transcription and translation
21.2 Gene expression
14
The genetic code
21.2 Gene expression
  • Made of 4 bases
  • Bases act as a code for amino acids in
    translation
  • Every 3 bases on the mRNA is called a codon that
    codes for a particular amino acid in translation

15
1. Transcription
21.2 Gene expression
  • mRNA is made from a DNA template
  • mRNA is processed before leaving the nucleus
  • mRNA moves to the ribosomes to be read
  • Every 3 bases on the mRNA is called a codon and
    codes for a particular amino acid in translation

16
Processing of mRNA after transcription
21.2 Gene expression
  • Modifications of mRNA
  • One end of the RNA is capped
  • Introns removed
  • Poly-A tail is added

17
2. Translation
21.2 Gene expression
  • 3 steps
  • Initiation mRNA binds to the small ribosomal
    subunit and causes 2 ribosomal units to associate
  • Elongation polypeptide lengthens
  • tRNA picks up an amino acid
  • tRNA has an anticodon that is complementary to
    the codon on the mRNA
  • tRNA anticodon binds to the codon and drops off
    an amino acid to the growing polypeptide
  • Termination a stop codon on the mRNA causes the
    ribosome to fall off the mRNA

18
Visualizing the 3 steps of translation
21.2 Gene expression
19
Regulation of gene expression
21.2 Gene expression
  • 4 levels
  • 1. Transcriptional control (nucleus)
  • e.g. chromatin density and transcription factors
  • 2. Posttranscriptional control (nucleus)
  • e.g. mRNA processing
  • 3. Translational control (cytoplasm)
  • e.g. Differential ability of mRNA to bind
    ribosomes
  • 4. Posttranslational control (cytoplasm)
  • e.g. changes to the protein to make it functional

20
An example of transcriptional control
21.2 Gene expression
21
What did we learn from the human genome project
(HGP)?
21.3 Genomics
  • Humans consist of about 3 billion bases and
    25,000 genes
  • Human genome sequenced in 2003
  • There are many polymorphisms or small regions of
    DNA that vary among individuals were identified
  • Genome size is not correlated with the number of
    genes or complexity of the organisms

22
What is the next step in the HGP?
21.3 Genomics
  • Functional genomics
  • Understanding how the 25,000 genes function
  • Understanding the function of gene deserts (82
    regions that make up 3 of the genome lacking
    identifiable genes)
  • Comparative genomics
  • Help understand how species have evolved
  • Comparing genomes may help identify base
    sequences that cause human illness
  • Help in our understanding of gene regulation

23
New endeavors
21.3 Genomics
  • Proteomics the study of the structure, function
    and interactions of cell proteins
  • Can be difficult to study because
  • protein concentrations differ greatly between
    cells
  • protein location, concentration interactions
    differ from minute to minute
  • understanding proteins may lead to the discovery
    of better drugs
  • Bioinformatics the application of computer
    technologies to study the genome

24
How can we modify a persons genome?
21.3 Genomics
  • Gene therapy - insertion of genetic material
    into human cells to treat a disorder
  • Ex vivo therapy cells are removed for a person
    altered and then returned to the patient
  • In vivo therapy a gene is directly inserted
    into an individual through a vector (e.g.
    viruses) or directly injected to replace mutated
    genes or to restore normal controls over gene
    activity
  • Gene therapy has been most successful in treating
    cancer

25
Ex vivo gene therapy
21.3 Genomics
26
DNA technology terms
21.4 DNA technology
  • Genetic engineering altering DNA in bacteria,
    viruses, plants and animal cells through
    recombinant DNA techonology
  • Recombinant DNA contains DNA from 2 or more
    different sources
  • Transgenic organisms organisms that have a
    foreign gene inserted into them
  • Biotechnology using natural biological systems
    to create a product or to achieve an end desired
    by humans

27
DNA technology
21.4 DNA technology
  • Gene cloning through recombinant DNA
  • Polymerase chain reaction (PCR)
  • DNA fingerprinting
  • Biotechnology products from bacteria, plants and
    animals

28
1. Gene cloning
21.4 DNA technology
  • Recombinant DNA contains DNA from 2 or more
    different sources that allows genes to be copies
  • An example using bacteria to clone the human
    insulin gene
  • Restriction enzyme used to cut the vector
    (plasmid) and the human DNA with the insulin gene
  • DNA ligase seals together the insulin gene and
    the plasmid
  • Bacterial cells uptake plasmid and the gene is
    copied and product can be made

29
Visualizing gene cloning
21.4 DNA technology
30
2. Polymerase chain reaction (PCR)
21.4 DNA technology
  • Used to clone small pieces of DNA
  • Important for amplifying DNA for analysis such as
    in DNA fingerprinting

31
3. DNA fingerprinting
21.4 DNA technology
  • Fragments are separated by their charge/size
    ratios
  • Results in a distinctive pattern for each
    individual
  • Often used for paternity or to identify an
    individual at a crime scene or unknown body
    remains

32
4. Biotechnology products Transgenic bacteria
21.4 DNA technology
  • Important uses
  • Insulin
  • Human growthhormone (HGH)
  • Clotting factor VIII
  • Tissue plasminogen activator (t-PA)
  • Hepatitis B vaccine
  • Bioremediation cleaning up theenvironment such
    as oil degradingbacteria

33
4. Biotechnology products Transgenic plants
21.4 DNA technology
  • Important uses
  • Produce human proteins in their seeds such as
    hormones, clotting factors and antibodies
  • Plants resistant to herbicides
  • Plants resistant to insects
  • Plants resistant to frost
  • Corn, soybean and cotton plants are commonly
    genetically altered
  • In 2001
  • 72 million acres of transgenic crops worldwide
  • 26 of US corn crops were transgenic crops

34
4. Biotechnology products Transgenic plants
21.4 DNA technology
35
Health focus Ecological concern about BT crops
21.4 DNA technology
  • Resistance increasing in the target pest
  • Exchange of genetic material between the
    transgenic plant and a related species
  • Concern about the impact of BT crops on nontarget
    species

36
4. Biotechnology products Transgenic animals
21.4 DNA technology
  • Gene is inserted into the egg that when
    fertilized will develop into a transgenic animal
  • Current uses
  • Gene pharming production of pharmaceuticals in
    the milk of farm animals
  • Larger animals includes fish, cows, pigs,
    rabbits and sheep
  • Mouse models the use of mice for various gene
    studies
  • Xenotransplantation pigs can express human
    proteins on their organs making it easier to
    transplant them into humans
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