Day 8 september 23rd 2014
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DNA Chromosomes Diabetes and Cancer
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Day 8 september 23rd 2014
- 1. Day 8 September 23rd 2014 Chapter 5 Dr. Amy B Hollingsworth The University of Akron
- 2. What exactly is a gene?
- 4. Almost everyone in the United States consumes genetically modified foods regularly without knowing it. What foods are responsible for this?
- 5. Insect Resistance Insert figure 5-33
- 6. How can genetically modified plants lead to reduced pesticide use by farmers?
- 9. Faster Growth and Bigger Bodies
- 10. 5.13 Fears and risks: Are genetically modified foods safe?
- 11. Fear #1: Organisms that we want to kill may become invincible. Fear #2: Organisms that we don’t want to kill may be killed inadvertently. Fear #3: Genetically modified crops are not tested or regulated adequately.
- 12. Fear #4: Eating genetically modified foods is dangerous. Fear #5: Loss of genetic diversity among crop plants is risky. Fear #6: Hidden costs may reduce the financial advantages of genetically modified crops.
- 13. 5.14–5.17 Biotechnology has the potential for improving human health (and criminal justice)
- 14. 5.14 The treatment of diseases and production of medicines are improved with biotechnology Prevent diseases Cure diseases Treating diseases • The treatment of diabetes
- 16. Why do some bacteria produce human insulin? Recombinant DNA technology
- 17. Several important achievements followed the development of insulin-producing bacteria, including: 1. Human growth hormone (HGH) 2. Erythropoietin
- 18. What is “blood doping”? How does it improve some athletes’ performance?
- 19. 5.15 Gene Therapy: biotechnology can help diagnose and prevent diseases But it has had a limited success in curing them
- 20. 1. Is a given set of parents likely to produce a baby with a genetic disease? Insert figure 5-41
- 21. 2. Will a baby be born with a genetic disease? cystic fibrosis sickle-cell anemia Down syndrome others
- 22. 3. Is an individual likely to develop a genetic disease later in life? breast cancer prostate cancer skin cancer
- 23. Ethical Dilemmas Discrimination Health insurance How to proceed with the information?
- 25. Why has gene therapy had such a poor record of success in curing diseases?
- 26. Gene Therapy Difficulties 1. Difficulty getting the working gene into the specific cells where it is needed. 2. Difficulty getting the working gene into enough cells and at the right rate to have a physiological effect.
- 27. Gene Therapy Difficulties 3. Difficulty arising from the transfer organism getting into unintended cells. 4. Difficulty regulating gene expression.
- 28. 5.16 Cloning—ranging from genes to organs to individuals—offers both promise and perils
- 31. Are there any medical justifications for cloning?
- 32. 5.17 DNA as an individual identifier: the uses and abuses of DNA fingerprinting
- 34. What is a DNA fingerprint?
- 35. Chapter 6: Chromosomes and Cell Division Insert new photo (Jackson 5) Continuity and variety Lectures by Mark Manteuffel, St. Louis Community College
- 36. There are different types of cell division. Mitosis and Meiosis
- 37. 6.1 Immortal cells can spell trouble: cell division in sickness and health.
- 38. Telomeres The telomere is like a protective cap at the end of the DNA. Every time a cell divides, the telomere gets a bit shorter. Insert new fig 6-1
- 39. Progeria – rarely live past 13
- 40. “Cancer cells are those which have forgotten how to die.” —Harold Pinter
- 41. 6.2 Some chromosomes are circular, others are linear.
- 43. 6.3 Prokaryotes divide by binary fission.
- 45. 6.5 Cell division is preceded by replication. Persistence and propagation
- 46. Replication The process of DNA duplication
- 47. Complementarity The characteristic that in the double-stranded DNA molecule the base on one strand always has the same pairing-partner (called the complementary base) on the other strand Every “A” (adenine) pairs with “T” (thymine) and vice-versa. Every “G” (guanine) pairs with “C” (cytosine) and vice-versa.
- 49. Errors sometime occur when DNA duplicates itself. Why might that be a good thing?
- 50. Mutation A variety of errors can occur during replication. Several DNA repair processes occur after replication. If an error remains, however, the sequences in a replicated DNA molecule (including the genes) can be different from those in the parent molecule.
- 51. 6.6 Most cells are not immortal: Mitosis generates replacements. What is dust? Why is it your fault?
- 52. Mitosis has just one purpose: To enable cells to generate new, genetically identical cells. There are two different reasons for this need: 1. Growth 2. Replacement
- 54. Apoptosis The pre-planned process of cell suicide Certain cells are targeted for apoptosis.
- 55. Mitosis The number of (somatic) cells that must be replaced by mitosis every day is huge. The rate at which mitosis occurs varies dramatically.
- 56. 6.7 Overview Mitosis leads to duplicate cells. Parent cells daughter cells
- 58. 6.8 The Details Mitosis is a four-step process.
- 59. Preparation for Mitosis: The Chromosomes Replicate
- 60. Animal chromosomes are linear. So why do they look like the letter “X” in pictures?
- 61. Sister Chromatids A chromosome and its identical replicated copy, joined at the centromere.
- 67. 6.9 Cell division out of control means cancer.
- 68. Cancer Unrestrained cell growth and division… …can lead to tumors… …the second leading cause of death in the United States! (20%, leading is heart disease)
- 69. Tumor Growth Unregulated cell division
- 70. Cancer cells have several features that distinguish them from normal cells, including…
- 71. Benign and Malignant Tumors
- 72. What is cancer? How does it usually cause death?
- 74. Why is the treatment for cancer often considered as bad as the disease?
- 75. Cancer is unrestrained cell growth and division. Cancer can lead to large masses of cells called malignant tumors that can cause serious health problems. Treatment focuses on killing or slowing the division of the cells using chemotherapy and/or radiation.
Editor's Notes
- Shortly after news of Dolly’s birth, teams set about cloning a variety of other species including mice, cows, pigs, and cats (Figure 5-44 Genetically identical cloned animals). Not all of this work was driven by simple curiosity. For farmers, cloning could have real value. It can take a long time to produce animals with desirable traits from an agricultural perspective—such as increased milk production in cows. And with each successive generation of breeding it can be difficult to maintain these traits in the population. But through the process of transgenic techniques and whole-animal cloning, large numbers of the valuable animals with such traits can be produced and maintained.
- Medical researchers, too, see much to gain from cloning. In particular, transgenic animals containing human genes—such as the hamsters producing rhu-EPO, discussed earlier—can be very valuable. But can a human be cloned? At this point, it is almost certain that the cloning of a human will be possible. Many people wonder, however, whether such an endeavor should be pursued. There is near unanimity among scientists that human cloning to produce children should not be attempted. Some of the reasons cited relate to problems of safety for the mother and the child, legal and philosophical issues relating to the inability of cloned individuals to give consent, problems of the exploitation of women, and concerns regarding identity and individuality. Governments are struggling to develop wise regulations for this new world.
- In another time, Colin Pitchfork, a murderer and rapist, would have walked free (Figure 5-45 Betrayed by his DNA). But in 1987, he was captured and convicted, betrayed by his DNA, and is now serving two life sentences in prison. Pitchford’s trouble began when he raped and murdered two 15-year-old high school girls in a small village in England in the 1980s. The police thought they had their perpetrator when a man confessed, but only to the second murder. He denied any involvement with the first murder, though, which perplexed the police because the details of the two crimes strongly suggested that the same person committed both. At the time, British biologist Alec Jeffreys made the important discovery that there were small pieces of DNA within every person’s chromosomes that were tremendously variable in their base sequences. In much the way each person has a driver’s license or Social Security number that differs from everyone else’s, these DNA fragments are variable enough that it is extremely unlikely that two people would ever have identical sequences at these locations. Thus, a comparison between these regions in a DNA sample from a person and in evidence left at a crime scene would enable police to determine that the evidence came from that person. Dr. Jeffreys analyzed DNA left by the murderer/rapist on the victims and found that it did indeed come from a single person, and that that person was not the man who originally confessed. That original suspect was released and has the distinction of being the first person cleared of a crime due to DNA fingerprinting. To track down the criminal, police then requested blood samples of all men in the area who were between 18- and 35-years-old, collecting and analyzing more than 5,000 blood samples. This led them to Colin Pitchfork, whose DNA matched perfectly the DNA left on both of the victims, and ultimately was the evidence responsible for his conviction. (He almost slipped through, having persuaded a friend to give a blood sample in his name. But when the friend was overheard telling the story in a pub, police tracked down Pitchfork to get a blood sample.)
- DNA fingerprinting is now used extensively in forensic investigations in much the same way that regular fingerprints have been used for the past 100 years. But traditional fingerprinting is limited in its usefulness for many crimes because no actual fingerprints are left behind. DNA fingerprinting, on the other hand, is not so limited because DNA samples more frequently are left behind, usually in the form of semen, blood, hair, skin, or other tissue. As a consequence, this technology has been directly responsible for bringing thousands of criminals to justice and, perhaps as importantly, for establishing the innocence of more than 200 people who were wrongly convicted of murder and other capital crimes. Let’s examine how DNA fingerprinting is done, why it is such a powerful forensic tool, and why it is not foolproof.
- For each STR locus analyzed, an individual’s genotype is determined by using PCR to amplify that region, then measuring the length of the STR region using electrophoresis. The length of the region can then be used to determine the number of times that the STR is repeated. For a single STR region, an individual’s genotype is two numbers, reflecting the number of STR repeats in the copies inherited from the mother and from the father. And a person’s full DNA fingerprint is a string of 26 numbers that includes the two numbers for each of 13 STRs. In court, a suspect’s genotype might be compared with the DNA fingerprint obtained from evidence found at the crime scene. DNA samples from different people will produce different 26-number “fingerprints,” whereas different samples of DNA from one person will have exactly the same genotype (FIGURE 5-47).
- Section 6-1 Opener Cell division by fission in Staphylococcus aureus, a disease-causing bacterium having resistance to multiple antibiotics.
- Once you are fully grown, do you have just one set of cells that live as long as you do? The answer is no: Your cells are continually dying off and the ones that remain divide and replace the cells you’ve lost, in an ongoing process. But how long can this last? Can it go on forever? And how does a cell even know how old it is?
- Just as a car comes with an odometer, which keeps track of how far the car has been driven, animal cells have a mechanism that keeps track of how many times the cell has divided. It’s a section of DNA, called the “telomere,” at the tip of every chromosome. Every time a cell divides, the telomere gets a bit shorter. Occurring right next to the valuable DNA sequences that specify genes, the telomere is like a protective cap at the end of the DNA. But after some critical number of cell divisions, with the telomere getting shorter and shorter each time, any additional cell divisions will cause the loss of functional, essential DNA, which means almost certain death for the cell (Figure 6-1 A cellular “odometer”).
- At birth, the telomeres in most human cells are long enough to support about 50 cell divisions. Occasionally, however, people are born with telomeres that are much shorter than normal. In these people, their cells and tissue begin to appear aged very soon after birth (Figure 6-2 Just a child). As a consequence, they rarely live beyond the age of 13.
- Look around your dorm room. Dust is everywhere. What is it? It is primarily dead skin cells. In fact, you and your roommates slough off millions of dead skin cells each day. Yet your skin is not disappearing. How can that be? Obviously, your body is replacing the sloughed off cells. The cells have simply worn out, so your body creates replacements, preferably identical copies of the old cells. How does it do this? Mitosis.
- 1. Growth. During growth and development, organisms get bigger and must add new cells. In fact, if you want to see cell division in action, one sure-fire place to look is at the tip of a plant root because that is one of the fastest growing parts of a plant, at about half an inch per day (Figure 6-7 Part 1 Reasons for mitosis).
- Some other cells that must be replaced actually die on purpose, in the pre-planned process of cell suicide called apoptosis. This seemingly counterproductive strategy is employed in parts of the body where the cells are likely to accumulate significant genetic damage over time and are therefore at high risk of becoming cancer cells (a process described later in this chapter). Cells targeted for apoptosis include many of the cells lining the digestive tract as well as those in the liver, two locations where cells are almost constantly in contact with harmful substances.
- Every day, a huge number of cells in an individual must be replaced by mitosis. In humans this number is in the billions. Nearly all of the somatic cells of the body—that is, everything other than sperm- and egg-producing cells—undergo mitosis with a few notable exceptions. Brain cells and heart muscle cells, in particular, do not appear to divide, or, if they do divide, they do so at very, very slow rates. (It is not known why this is so.) The rate at which mitosis occurs varies dramatically. The most rapid cell division occurs in the blood and among the cells lining various tissues and organs. The average red blood cell, for example, is in circulation only for about six weeks and then must be replaced, and the cells lining the intestines are replaced about every three weeks. Hair follicles, too, are among the most rapidly dividing cells.
- For mitosis to begin, the parent cell replicates its DNA, creating a duplicate copy of each chromosome. Once this task is completed, the remainder of mitosis can take place, in which the chromosomes are separated into identical sets in two separate nuclei, and then the cell can divide into two duplicate cells, the daughter cells.
- Mitosis occurs in just four steps. It cannot begin, however, until after an important event occurs during the previous portion of the cell cycle, interphase. During the synthesis portion of interphase, all of the chromosomes replicate. Mitosis then begins with 1) the condensing of the chromosomes, which during interphase are all stretched out and stringy. 2) Next, all of the duplicated and condensed pairs of chromosomes move to the center of the cell. 3) Each chromosome is pulled apart from its duplicate. 4) And finally, new cell membranes form around each complete set of chromosomes and the cytoplasm duplicates as well. Where once there was one cell, now there are two (Figure 6-10 A simplified introduction to mitosis).
- Let’s look at the process in a bit more detail, keeping in mind that the ultimate consequence of the process is to produce two cells with identical chromosomes. Interphase: in preparation for mitosis, the chromosomes replicate—Processes essential to cell division take place even before the mitotic phase of the cell cycle begins. During the DNA synthesis part of interphase, every chromosome creates an exact duplicate of itself by replicating. Prior to replication, each chromosome was just a long linear strand of genetic material. Following replication each chromosome is a pair of identical long linear strands, held together at the center, a position called the centromere. (Figure 6-11 Part 1 Mitosis: cell duplication, step by step). Mitosis 1) The long, linear chromosomes that have replicated condense—Looking at a cell through a microscope, you won’t generally see any chromosomes. Mitosis officially begins when the chromosomes in the cell’s nucleus become more and more tightly coiled. As they condense, they become thick enough that they can be seen through a light microscope.