1. Chapter 21 DNA Biology and Technology
Mader, Sylvia S. Human Biology. 13th Edition. McGraw-Hill, 2014.

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
a nitrogenous base
Sugar and phosphate make up the backbone while the bases make up the “rungs” of the ladder
Bases have complementary pairing
cytosine (C) pairs with guanine (G)
adenine (A) pairs with thymine (T)

5. The Bases
Figure 2–22b, c

6. 21.1 DNA and RNA structure and function
DNA structure

7. How does DNA replicate? 1. Two strands unwind by breaking the H bonds
21.1 DNA and RNA structure and function
How does DNA replicate?
1. Two strands unwind by breaking the H bonds
2. Complementary nucleotides are added to each strand by DNA polymerase
3. 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

8. DNA Replication DNA helicases unwind the DNA and separates the strands
DNA polymerase bind to the DNA and synthesizes complementary antiparallel strands
DNA rewinds into double helix molecules
New molecules contains one strand of the original DNA and one newly synthesized strand

9. 21.1 DNA and RNA structure and function
DNA replication

10. Mutations
Cell has repair enzymes that usually fix errors in DNA replication
A replication error that persists is a mutation
A permanent change in the sequence of bases that can cause a change in phenotype and introduce variability
Most non-infectious disease, conditions, and disorders are due to mutations in the DNA that change the amino acids in the protein
Point mutations
change in 1 base of DNA can be a silent mutation if the amino acids is not changed
Insertion mutation
addition of a base which changes the reading frame
whole protein after the mutation is wrong
Deletion Mutation
removal of a base, alter reading frame, wrong protein is made

11. 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

12. 21.1 DNA and RNA structure and function

13. 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
DNA has a deoxyribose sugar while RNA has a ribose sugar
RNA is also found in the cytoplasm as well as the nucleus while DNA is not

14. Gene Expression
DNA provides the cell with blueprints for synthesizing proteins
DNA resides in the nucleus and protein synthesis occurs in the cytoplasm
mRNA carries a copy of DNA’s blueprint into the cytoplasm
Other RNA molecules (rRNA and tRNA) are involved in protein synthesis

15. 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

16. Proteins: A review of structure

17. 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

18. Overview of transcription and translation

19. 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

20. Step 1: Gene Activation Uncoils DNA
Start and stop codes on DNA mark location of gene
Locates area for mRNA transcription

21. Step 2: DNA to mRNA Enzyme RNA polymerase transcribes DNA:
binds to promoter (start) sequence
reads DNA code for gene
binds nucleotides to form messenger RNA (mRNA)
mRNA duplicates DNA coding strand, uracil replaces thymine

22. Step 3: RNA Processing
At stop signal, mRNA detaches from DNA molecule:
code is edited (RNA processing)
unnecessary codes (introns) removed
good codes (exons) spliced together
triplet of 3 nucleotides (codon) represents one amino acid

23. 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

24. Processing of mRNA after transcription
Modifications of mRNA:
One end of the RNA is capped
Introns removed
Poly-A tail is added
important for the nuclear export, translation and stability of mRNA

25. Processing of mRNA after transcription
mRNA Splicing
Cells use only certain exons rather then all to form a mature RNA transcript
Result can be a different protein product in each cell
Alternate mRNA splicing may account for the ability of a single gene to result in two different proteins in a cell

26. 2. Translation 1. Initiation 2. Elongation: polypeptide lengthens
21.2 Gene expression
2. Translation
1. Initiation
- mRNA binds to the small ribosomal subunit and causes 2 ribosomal units to associate
2. 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
3. Termination
- a stop codon on the mRNA causes the ribosome to fall off the mRNA

28. Overview of transcription and translation

29. Regulation of gene expression
1. Transcriptional control (nucleus):
chromatin density  must decondense to allow for activation
transcription factors  DNA-bind proteins regulate activity of a gene
2. Posttranscriptional control (nucleus)
mRNA processing
3. Translational control (cytoplasm)
Differential ability of mRNA to bind ribosomes
4. Posttranslational control (cytoplasm)
changes to the protein to make it functional

30. What did we learn from the human genome project (HGP)?
Genes are a sequence of DNA bases that is transcribed into RNA molecules and may be translated into protein
Humans consist of about 3 billion bases (A,T,G,C) and 25,000 genes
Human genome sequenced in 2003
Many polymorphisms or small regions of DNA that vary among individuals were identified
Some have not physiological effects
Others contribute to the diversity of human beings and possibly disease
Genome size is not correlated with the number of genes or complexity of the organisms

31. 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

32. 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
May allow scientists to find cause-and-effect relationships between genetic profiles and disorders caused by multifactorial genes

33. 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

34. Ex vivo gene therapy Retrovirus
-RNA virus that is replicated in a host cell via the enzyme reverse
transcriptase to produce DNA from its RNA genome.
- DNA is incorporated into the host's genome
- Virus replicates as part of the host cell's DNA.

35. DNA technology terms Genetic engineering Recombinant DNA
altering DNA in bacteria, viruses, plants and animal cells through recombinant DNA technology
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

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

37. 21.4 DNA technology
1. Gene cloning
Recombinant DNA – contains DNA from 2 or more different sources that allows genes to be copies
The gene of interest is inserted into a vector
Vector is typically a plasmid, small accessory rings of DNA found in bacteria
An example using bacteria to clone the human insulin gene:
Restriction enzyme
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

39. 2. Polymerase chain reaction (PCR)
21.4 DNA technology
2. Polymerase chain reaction (PCR)
Used to clone small pieces of DNA
Requires
DNA polymerase to carry out DNA replication
Nucleotides (phosphate, deoxyribose, and base)
Important for amplifying DNA for analysis such as in DNA fingerprinting

40. 21.4 DNA technology
3. DNA fingerprinting
DNA 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

41. 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

42. 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

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

44. 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