1. Chapter 21
DNA Biology and Technology

2. Points to Ponder What are three functions of DNA?
Review DNA and RNA structure.
What are the 3 types of RNA and what are their functions?
Compare and contrast the structure and function of DNA and RNA.
How does DNA replicate?
Describe transcription and translation in detail.
Describe the genetic code.
Review protein structure and function.
What are the 4 levels of regulating gene expression.
What did we learn from the human genome project and where are we going from here?
What is ex vivo and in vivo gene therapy?
Define biotechnology, transgenic organisms, genetic engineering and recombinant DNA.
What are some uses of transgenic bacteria, plants and animals?

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

4. DNA structure: A review
21.1 DNA and RNA structure and function
DNA structure: A review
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)

5. 21.1 DNA and RNA structure and function
DNA structure

6. How does DNA replicate? The two strands unwind by breaking the H bonds
21.1 DNA and RNA structure and function
How does DNA replicate?
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

7. 21.1 DNA and RNA structure and function
DNA replication

8. RNA structure and function
21.1 DNA and RNA structure and function
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

9. 21.1 DNA and RNA structure and function

10. Comparing DNA and RNA Similarities: Differences: Are nucleic acids
21.1 DNA and RNA structure and function
Comparing DNA and RNA
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

11. Proteins: A review Composed of subunits of amino acids
21.2 Gene expression
Proteins: A review
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

12. Proteins: A review of structure
21.2 Gene expression
Proteins: A review of structure

13. 2 steps of 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

14. Overview of transcription and translation
21.2 Gene expression
Overview of transcription and translation

15. The genetic code Made of 4 bases
21.2 Gene expression
The genetic code
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

16. 1. Transcription mRNA is made from a DNA template
21.2 Gene expression
1. Transcription
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

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

18. 21.2 Gene expression
2. Translation
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

19. Visualizing the 3 steps of translation
21.2 Gene expression
Visualizing the 3 steps of translation

20. Regulation of 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

21. An example of transcriptional control
21.2 Gene expression
An example of transcriptional control

22. What did we learn from the human genome project (HGP)?
21.3 Genomics
What did we learn from the human genome project (HGP)?
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

23. What is the next step in the HGP?
21.3 Genomics
What is the next step in the HGP?
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

24. 21.3 Genomics
New endeavors
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

25. How can we modify a person’s genome?
21.3 Genomics
How can we modify a person’s genome?
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

26. 21.3 Genomics
Ex vivo gene therapy

27. 21.4 DNA technology
DNA technology terms
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

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

29. 21.4 DNA technology
1. Gene cloning
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

30. Visualizing gene cloning
21.4 DNA technology
Visualizing gene cloning

31. 2. Polymerase chain reaction (PCR)
21.4 DNA technology
2. Polymerase chain reaction (PCR)
Used to clone small pieces of DNA
Important for amplifying DNA for analysis such as in DNA fingerprinting

32. 21.4 DNA technology
3. DNA fingerprinting
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

33. 4. Biotechnology products: Transgenic bacteria
21.4 DNA technology
4. Biotechnology products: Transgenic bacteria
Important uses:
Insulin
Human growth hormone (HGH)
Clotting factor VIII
Tissue plasminogen activator (t-PA)
Hepatitis B vaccine
Bioremediation – cleaning up the environment such as oil degrading bacteria

34. 4. Biotechnology products: Transgenic plants
21.4 DNA technology
4. Biotechnology products: Transgenic plants
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

35. 4. Biotechnology products: Transgenic plants
21.4 DNA technology
4. Biotechnology products: Transgenic plants

36. Health focus: Ecological concern about BT crops
21.4 DNA technology
Health focus: Ecological concern about BT crops
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

37. 4. Biotechnology products: Transgenic animals
21.4 DNA technology
4. Biotechnology products: Transgenic animals
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