Presentation is loading. Please wait.

Presentation is loading. Please wait.

F.3.1 – F 3.5 F3 Microbes and biotechnology. F. 3.1 State that reverse transcriptase catalyzes the production of RNA to DNA.

Similar presentations


Presentation on theme: "F.3.1 – F 3.5 F3 Microbes and biotechnology. F. 3.1 State that reverse transcriptase catalyzes the production of RNA to DNA."— Presentation transcript:

1 F.3.1 – F 3.5 F3 Microbes and biotechnology

2 F. 3.1 State that reverse transcriptase catalyzes the production of RNA to DNA

3 ›Reverse transcriptase is an enzyme isolated from retroviruses which catalyses the production of DNA from an RNA template

4 RNA as Viral Genetic Material ›The broadest variety of RNA genomes is found in viruses that infect animals ›Retroviruses use reverse transcriptase to copy their RNA genome into DNA ›HIV (human immunodeficiency virus) is the retrovirus that causes AIDS (acquired immunodeficiency syndrome) © 2011 Pearson Education, Inc.

5 Glycoprotein Reverse transcriptase HIV Viral envelope Capsid RNA (two identical strands) HOST CELL Viral RNA Reverse transcriptase RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus HIV Membrane of white blood cell 0.25  m HIV entering a cell New HIV leaving a cell Figure 19.8

6 Glycoprotein Reverse transcriptase HIV Viral envelope Capsid RNA (two identical strands) HOST CELL Viral RNA Reverse transcriptase RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus Figure 19.8a

7 Figure 19.8b HIV Membrane of white blood cell HIV entering a cell New HIV leaving a cell 0.25  m

8 ›The viral DNA that is integrated into the host genome is called a provirus ›Unlike a prophage, a provirus remains a permanent resident of the host cell ›The host’s RNA polymerase transcribes the proviral DNA into RNA molecules ›The RNA molecules function both as mRNA for synthesis of viral proteins and as genomes for new virus particles released from the cell © 2011 Pearson Education, Inc.

9 Animation: HIV Reproductive Cycle Right-click slide / select “Play”

10 F. 3.2 Explain how reverse transcriptase is used in molecular biology

11 ›A complementary DNA (cDNA) library is made by cloning DNA made in vitro by reverse transcription of all the mRNA produced by a particular cell ›A cDNA library represents only part of the genome— only the subset of genes transcribed into mRNA in the original cells © 2011 Pearson Education, Inc.

12 ›Reverse transcriptase is used as part of recombinant DNA technology to produce genes for gene transfer ›The enzyme catalyses the production of a complementary (single) strand of copy DNA (cDNA) from an mRNA template ›As RNA undergoes post-transcriptional modification (i.e. splicing) prior to forming mRNA, cDNA does not contain introns ›As bacteria lack the machinery for intron removal, genes spliced into bacterial hosts need introns removed in order to generate functional proteins ›Examples of how reverse transcriptase has been used in molecular biology include: –The mass production of human insulin by E. coli cells –The generation of cDNA libraries for use in DNA microarrays (DNA fingerprinting)

13 Figure DNA in nucleus mRNAs in cytoplasm

14 Figure DNA in nucleus mRNAs in cytoplasm mRNA Reverse transcriptase Poly-A tail DNA strand Primer A A A T T T T T

15 Figure DNA in nucleus mRNAs in cytoplasm mRNA Reverse transcriptase Poly-A tail DNA strand Primer A A A T T T T T

16 Figure DNA in nucleus mRNAs in cytoplasm mRNA Reverse transcriptase Poly-A tail DNA strand Primer DNA polymerase A A A T T T T T

17 Figure DNA in nucleus mRNAs in cytoplasm mRNA Reverse transcriptase Poly-A tail DNA strand Primer DNA polymerase cDNA A A A T T T T T

18 F.3.3 Distinguish between somatic and germ line therapy

19 Gene therapy is the insertion of genes into an individual's cells and tissues in order to treat genetic diseases

20 What is gene therapy? F.3.4 Outline the use of viral vectors in gene therapy

21 Concept 20.4: The practical applications of DNA technology affect our lives in many ways ›Many fields benefit from DNA technology and genetic engineering © 2011 Pearson Education, Inc.

22 Human Gene Therapy ›Gene therapy is the alteration of an afflicted individual’s genes ›Gene therapy holds great potential for treating disorders traceable to a single defective gene ›Vectors are used for delivery of genes into specific types of cells, for example bone marrow ›Gene therapy provokes both technical and ethical questions © 2011 Pearson Education, Inc.

23 Figure Cloned gene Retrovirus capsid Bone marrow cell from patient Viral RNA Bone marrow Insert RNA version of normal allele into retrovirus. Let retrovirus infect bone marrow cells that have been removed from the patient and cultured. Viral DNA carrying the normal allele inserts into chromosome. Inject engineered cells into patient.

24 ›Viral vectors have been used to facilitate the replacement of defective genes with healthy, functional copies ›Individuals with severe combined immunodeficiency (SCID) may have be unable to synthesize the enzyme adenosine deaminase (ADA) ›White blood cells or bone marrow cells are removed and, using a viral vector, a copy of the normal gene is integrated into the cell's genome ›When the cells are replaced in the body of the patient the normal gene is expressed, resulting in the production of ADA and the treatment of SCID ›There are still technical problems to be solved before this becomes viable technology – e.g. ensuring correct amount at right time and place

25

26 F.3.5 Discuss the risks of gene therapy

27 Safety and Ethical Questions Raised by DNA Technology ›Potential benefits of genetic engineering must be weighed against potential hazards of creating harmful products or procedures ›Guidelines are in place in the United States and other countries to ensure safe practices for recombinant DNA technology © 2011 Pearson Education, Inc.

28 ›Most public concern about possible hazards centers on genetically modified (GM) organisms used as food ›Some are concerned about the creation of “super weeds” from the transfer of genes from GM crops to their wild relatives ›Other worries include the possibility that transgenic protein products might cause allergic reactions © 2011 Pearson Education, Inc.

29 ›As biotechnology continues to change, so does its use in agriculture, industry, and medicine ›National agencies and international organizations strive to set guidelines for safe and ethical practices in the use of biotechnology © 2011 Pearson Education, Inc.

30 ›Undesirable health effects (e.g. cancers / death) ›If gene insertion occurs in the wrong location it may affect the functioning of pre-existing genes that are vital within the genome ›Viral vectors may infect healthy cells or tissues ›Virus may revert to original form (mutate) and become pathogenic ›Virus entry may trigger an immune response leading to inflammation, toxicity and organ failure ›Treatment must be repeated at regular intervals, increasing likelihood of adverse treatment response with time Risks associated with Gene Therapy


Download ppt "F.3.1 – F 3.5 F3 Microbes and biotechnology. F. 3.1 State that reverse transcriptase catalyzes the production of RNA to DNA."

Similar presentations


Ads by Google