1. Genetically Modified Organisms Gene Expression, Mutation, and Cloning
Chapter 7
Genetically Modified Organisms Gene Expression, Mutation, and Cloning

2. 1 Protein Synthesis and Gene Expression
In the early 1980s, genetic engineers began producing recombinant bovine growth hormone (rBGH)
Made by genetically engineered bacteria
The bacteria were given DNA that carries instructions for making BGH
In cows, growth hormones increase body size and milk production

3. 1 Protein Synthesis and Gene Expression: From Gene to Protein
Protein synthesis – the process of using instructions carried on a gene to create proteins.
Several steps are involved and require both DNA and RNA.
Gene – a sequence of DNA that encodes a protein
Protein – a large molecule composed of amino acids

4. 1 Protein Synthesis and Gene Expression: From Gene to Protein
DNA
Double-stranded
Each nucleotide composed of deoxyribose, phosphate, and nitrogenous base
4 bases: adenine, thymine, guanine, cytosine

5. 1 Protein Synthesis and Gene Expression: From Gene to Protein
RNA
Single-stranded
Nucleotides comprised of ribose, phosphate, and nitrogenous base
4 bases: A, T, G, and Uracil

6. 1 Protein Synthesis and Gene Expression: From Gene to Protein
The flow of genetic information in a cell is DNA  RNA  protein and occurs in 2 steps:
Transcription (DNA  RNA)
Translation (RNA  Protein)

7. 1 Protein Synthesis and Gene Expression: Transcription
Transcription occurs in the nucleus.
RNA polymerase binds to the promoter region of the gene.
RNA polymerase zips down the length of gene, matching RNA nucleotides with complementary DNA nucleotides
This forms messenger RNA (mRNA)

8. Animation: Transcription
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9. 1 Protein Synthesis and Gene Expression: Translation
Translation occurs in the cytoplasm (outside the nucleus).
Translation requires: mRNA (made during transcription), amino acids, energy (ATP), and some helper molecules.
Ribosomes
Transfer RNA (tRNA)

10. 1 Protein Synthesis and Gene Expression: Translation
Ribosomes
The ribosome is composed of ribosomal RNA (rRNA) and comprises a small and a large subunit.

11. 1 Protein Synthesis and Gene Expression: Translation
Transfer RNA: tRNA carries amino acids and matches its anticodon with codons on mRNA
Codons are 3 nucleotides long

12. 1 Protein Synthesis and Gene Expression: Translation
A protein is put together one amino acid at a time.
The ribosome attaches to the mRNA at the promoter region.
Ribosome facilitates the docking of tRNA anticodons to mRNA codons.
When two tRNAs are adjacent, a bond is formed between their amino acids.
Forms a peptide chain of amino acid

13. 1 Protein Synthesis and Gene Expression: Translation

14. 1 Protein Synthesis and Gene Expression: Translation

15. 1 Protein Synthesis and Gene Expression: Genetic Code
The genetic code allows a specific codon to code for a specific amino acid.
A codon is comprised of three nucleotides = 64 possible combinations (43 combinations)
61 codons code for amino acids
3 others are stop codons, which end protein synthesis
Genetic code expresses redundancy
The genetic code is universal

16. 1 Protein Synthesis and Gene Expression: Genetic Code

17. BioFlix: Protein Synthesis
Animation: Translation
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BioFlix: Protein Synthesis

18. 1 Protein Synthesis and Gene Expression: Mutations
Changes in genetic sequence = mutations
Changes in genetic sequence might affect the order of amino acids in a protein.
Protein function is dependent on the precise order of amino acids
Possible outcomes of mutation:
1 - no change in protein
2 - non-functional protein
3 - different protein

19. 1 Protein Synthesis and Gene Expression: Mutation
Base-substitution mutation
Simple substitution of one base for another

20. 1 Protein Synthesis and Gene Expression: Mutation
Neutral mutation
Mutation does not change the function of the protein, it codes for the same amino acid

21. 1 Protein Synthesis and Gene Expression: Mutation
Frameshift mutation
Addition or deletion of a base, which changes the reading frame

22. 1 Protein Synthesis and Gene Expression: An Overview of Gene Expression
Each cell in your body (except sperm and egg cells) has the same DNA.
But each cell only expresses a small percentage of genes.
Example: Nerve and muscle cells perform very different functions, thus they use different genes.
Turning a gene or a set of genes on or off = regulating gene expression

23. 1 Protein Synthesis and Gene Expression: An Overview of Gene Expression
Nerves and cells have the same suite of genes, but they express different genes.

24. 1 Protein Synthesis and Gene Expression: Regulating Gene Expression
Regulation of transcription
Prokaryotic cells use repressors to regulate gene expression
Repressors bind to the promoter and prevent the RNA polymerase from binding

25. 1 Protein Synthesis and Gene Expression: Regulating Gene Expression
Regulation of transcription
Eukaryotic cells use activators to regulate gene expression
Activators help the RNA polymerase bind to the promoter

26. 1 Protein Synthesis and Gene Expression: Regulating Gene Expression
Regulation by chromosome condensation
Folding up of the chromosomes prevents transcription
Regulation by mRNA degradation
Nucleases cut mRNA
Regulation of Translation
Slowing of binding of the mRNA to the ribosome
Regulation of Protein Degradation
Proteases degrade proteins

27. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
rBGH is a protein, and is coded by a specific gene.
Transfer of rBGH gene to bacteria allows for growth under ideal conditions.
Bacteria can serve as “factories” for production of rBGH.
Cloning of the gene is making many copies of that gene.

28. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
Restriction enzymes – Used by bacteria as a form of defense. Restriction enzymes cut DNA at specific sequences. They are important in biotechnology because they allow scientists to make precise cuts in DNA.
Plasmid – Small, circular piece of bacterial DNA that exists separate from the bacterial chromosome. Plasmids are important because they can act as a ferry to carry a gene into a cell.

29. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
Step 1. Remove the gene from the cow chromosome

30. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
Step 2. Insert the BGH gene into the bacterial plasmid

31. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
Recombinant – Indicates material that has been genetically engineered: a gene that has been removed from its original genome and combined with another.
After step 2, the GBH is now referred to as recombinant GBH or rGBH.

32. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
Step 3. Insert the recombinant plasmid into a bacterial cell

33. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria
About 1/3 of cows in the US are injected with rBGH. rBGH increases milk volume from cows by about 20%.
The same principles apply to other proteins.
Clotting proteins for hemophiliacs are produced using similar methods.
Insulin for diabetics is also produced in this way.
FDA approval is needed for any new food that is not generally recognized as safe (GRAS).

34. Animation: Producing Bovine Growth Hormone
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36. 3 Genetically Modified Foods
All agricultural products are the result of genetic modification through selective breeding. Artificial selection does not move genes from one organism to another, but does drastically change the characteristics of a population.
Genetically modifying foods
Increase shelf life, yield, or nutritional value
Golden rice has been genetically engineered to produce beta-carotene, which increases the rice’s nutritional yield.

37. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun
Unlike rBGH, crop plants are directly modified. In order to do this, the target gene must be inserted into the plant cell. Two methods to do this:
Ti plasmid
Gene gun

38. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid

39. 3 Genetically Modified Foods: Modifying Plants with the Gene Gun

40. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun
Transgenic organism – the result of the incorporation of a gene from one organism to the genome of another. Also referred to as a genetically modified organism (GMO).
Benefits: Crops can be engineered for resistance to pests, thus farmers can spray fewer chemicals.
Concerns: Pests can become resistant to chemicals. GM crops may actually lead to increased use of pesticides and herbicides. GM crop plants may transfer genes to wild relatives.

41. 4 Genetically Modified Humans: Stem Cells
Stem cells – undifferentiated cells, capable of growing in to many different kinds of cells and tissues
Stems cells might be used to treat degenerative diseases such as Alzheimer’s or Parkinson’s.
Using stem cells to produce healthy tissue is called therapeutic cloning.
Stem cells could also be used to grow specific tissues to treat burns, heart attack damage, or replacement cartilage in joints.
Stems cells are totipotent, meaning they can become any other cell in the body.

42. 4 Genetically Modified Humans: Human Genome Project
Human Genome Project – international effort to map the sequence of the entire human genome (~20,000 – 25,000 genes).
For comparative purposes, genomes of other model organisms (E. coli, yeast, fruit flies, mice) were also mapped.
It was sequenced using the technique of chromosome walking.

43. 4 Genetically Modified Humans: Gene Therapy
Gene therapy – replacement of defective genes with functional genes
Germ line gene therapy
Embryonic treatment
Embryo supplied with a functional version of the defective gene.
Embryo + cells produced by cell division have a functional version of gene.
Somatic cell gene therapy
Somatic cell gene therapy – fix or replace the defective protein only in specific cells

44. 4 Genetically Modified Humans: Gene Therapy
Somatic cell therapy used as a treatment of SCID (severe combined immunodeficiency)
All somatic cells have limited lifetimes.
Therapy is not permanent and requires several treatments per year.

45. 4 Genetically Modified Humans: Cloning Humans
Human cloning occurs naturally whenever identical twins are produced.
Cloning of offspring from adults has already been done with cattle, goats, mice, cats, pigs, and sheep.
Cloning is achieved through the process of nuclear transfer.

46. 4 Genetically Modified Humans: Cloning Humans

47. Which of the following types of RNA carries amino acids to the growing polypeptide chain?
mRNA
tRNA
rRNA
RNA does not carry amino acids
Answer: B
Transfer RNAs carry amino acids. Messenger RNAs are complementary to the DNA. Ribosomal RNAs make up ribosomes. 47

48. Which of the following types of RNA carries amino acids to the growing polypeptide chain?
mRNA
tRNA
rRNA
RNA does not carry amino acids 48

49. A sequence of mRNA, called a codon, reads ACU
A sequence of mRNA, called a codon, reads ACU. How will the set of nucleotides on the anticodon of the tRNA read?
ACU
UGA
TGA
AUG
Answer: B
The anticodon of the tRNA is complimentary to the codon. UGA is the only sequence that is complimentary to ACU. 49

50. A sequence of mRNA, called a codon, reads ACU
A sequence of mRNA, called a codon, reads ACU. How will the set of nucleotides on the anticodon of the tRNA read?
ACU
UGA
TGA
AUG 50

51. Which of the following regulation techniques will result in increased gene expression?
condensing the chromosome
speeding up proteases
lengthening the adenosine nucleotide “tail”
slowing the movement of the mRNA through the ribosome
Answer: C
The poly-A tail protects the mRNA from nucleases. Condensing the chromosome, speeding up proteases, and slowing the movement of the mRNA through the ribosome would decrease gene expression. 51

52. Which of the following regulation techniques will result in increased gene expression?
condensing the chromosome
speeding up proteases
lengthening the adenosine nucleotide “tail”
slowing the movement of the mRNA through the ribosome 52

53. Which of the following statements is accurate?
The plasmid is cut with the same restriction enzyme as the removed gene.
The plasmid is a circular piece of RNA.
The plasmid is part of the bacterial chromosome.
The plasmid replicates when the bacterial chromosome replicates.
Answer: A
The same restriction enzyme is used to cut open the plasmid and to remove the gene of interest. This creates complementary sticky ends. Plasmids are circular pieces of DNA and exist separately from the bacterial chromosome. They replicate independently of the bacterial chromosome. 53

54. Which of the following statements is accurate?
The plasmid is cut with the same restriction enzyme as the removed gene.
The plasmid is a circular piece of RNA.
The plasmid is part of the bacterial chromosome.
The plasmid replicates when the bacterial chromosome replicates. 54

55. Which of the following statements concerning rBGH-treated milk is correct?
The injected cows produce 20% more milk.
There is no evidence of the hormone being transferred to the milk.
Humans would be able to safely digest the hormone, just like any other protein in food.
All of the statements are correct.
Answer: D
All of these facts were taken into account when the FDA declared that rBGH-treated milk is safe to consume. 55

56. Which of the following statements concerning rBGH-treated milk is correct?
The injected cows produce 20% more milk.
There is no evidence of the hormone being transferred to the milk.
Humans would be able to safely digest the hormone, just like any other protein in food.
All of the statements are correct. 56

57. Which of the following was used to treat SCID patients?
therapeutic cloning
nuclear transfer
somatic gene therapy
germ line gene therapy
Answer: C
Somatic gene therapy is the taking of cells from a person and injecting it with the functional gene and then allow the cell to reproduce and then place the copies of the good cells back into the body. 57

58. Which of the following was used to treat SCID patients?
therapeutic cloning
nuclear transfer
somatic gene therapy
germ line gene therapy 58

59. Which of the following statements is incorrect?
Stem cells are undifferentiated.
Stem cells are totipotent.
Specialized stem cells divide to make undifferentiated stem cells.
Stem cells can be used for therapeutic cloning.
Answer: C
Once stem cells have specialized, they cannot backtrack to become a different type of cell. Stem cells are undifferentiated and totipotent. They can be used for therapeutic cloning. 59

60. Which of the following statements is incorrect?
Stem cells are undifferentiated.
Stem cells are totipotent.
Specialized stem cells divide to make undifferentiated stem cells.
Stem cells can be used for therapeutic cloning. 60

61. When scientists try to replace defective human genes with functional genes they are performing ________.
gene therapy
in vitro fertilization
therapeutic cloning
nuclear transfer
Answer: A
Gene therapy is the process of replacing defective genes with functional genes. In vitro fertilization is a fertility treatment resulting in excess embryos. Therapeutic cloning uses stem cells to produce healthy tissues. Nuclear transfer occurs when mammary gland cells are fused with an egg cell that has its nucleus removed. 61

62. When scientists try to replace defective human genes with functional genes they are performing ________.
gene therapy
in vitro fertilization
therapeutic cloning
nuclear transfer 62

63. What is happening in step 1 in this figure?
The embryo is being grown in culture.
The egg cell and mammary cell are fused together.
The nucleus is removed from the egg cell.
The embryo is being implanted into the uterus of a third sheep.
Answer: C
The mammary cells and egg cell are isolated from two sheep and the nucleus is then removed from the egg cell. The egg cell and mammary cell are then fused together. The embryo is grown in culture and then implanted into the uterus of a third sheep. 63

64. What is happening in step 1 in this figure?
The embryo is being grown in culture.
The egg cell and mammary cell are fused together.
The nucleus is removed from the egg cell.
The embryo is being implanted into the uterus of a third sheep. 64

65. When undergoing recombination, _______.
the plasmid and the cow gene are cut with different restriction enzymes
the recombinant plasmid is reinserted into the cow’s cell to increase milk production
the rBGH genes are injected into cows to increase their milk production
the recombinant plasmid is inserted in bacterium, making large quantities of rBGH proteins
Answer: D
In order to create recombinant BGH, you need to combine the bacteria plasmid with the gene that produces milk from the cow DNA. In order to do this the plasmid and cow BGH gene are cut with the same restriction enzyme. This allows for the two to have sticky ends which will allow the plasmid and the cow gene to combine into one. The recombinant plasmid is then reinserted into the bacterium. The rBGH genes produce large quantities of rBGH proteins insidie the bacterium, which are harvested, purified, and then injected into the cows. 65

66. When undergoing recombination, _______.
the plasmid and the cow gene are cut with different restriction enzymes
the recombinant plasmid is reinserted into the cow’s cell to increase milk production
the rBGH genes are injected into cows to increase their milk production
the recombinant plasmid is inserted in bacterium, making large quantities of rBGH proteins 66