Don’t forget!

1. Don’t forget! The Animal Science department welcomes you back on Wednesday at the Campbell Avenue Farm! 4:30 PM; come for burgers, games and the chance to dunk faculty members of your choice Find out about ANS clubs and Ag student organizations If you need more information, a ride or directions, contact Maryann Harris maharris@ag.arizona.edu

2. The website is up! The website is: http://ag.arizona.edu/classes/ans213/ PLEASE NOTE: I WILL BE UPDATING THE LECTURES AND HOMEWORK PROBLEMS AS I GO. CHECK THE WEBSITE FREQUENTLY FOR UP-TO-DATE INFORMATION

3. The Website…pre-emptive questions I have replaced Lectures 1 and 2 with copies that delete the color background. This will continue. Color printing may still be helpful as I highlight words and concepts along the way Lectures will be posted in both Acrobat and Powerpoint formats so you can choose your style.

4. Pre-emptive questions, cont. The homework questions will not be collected or graded, but I might use some on the exam. The homework questions will not be collected or graded, but they might show up on a test or the final.

5. Pre-emptive questions, cont. If you can answer the assigned problems and understand the concepts, you will probably do very well on the test. It’s a very good idea to go over the assigned problems. In fact, do ALL the problems. It won’t hurt you.

6. “It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it is possible to find them.” J. Robert Oppenheimer, director of the Manhattan Project that drove development of nuclear weapons in the US during WW II.

7. Genetics in the News For full text, see www.pnas.org/cgi/doi/10.1073/pnas.0403639101

8. Turning Slackers Into Workaholics  Reuters 03:15 PM Aug. 11, 2004 PT Procrastinating monkeys were turned into workaholics using a gene treatment to block a key brain compound, U.S. researchers reported on Wednesday. Blocking cells from receiving dopamine made the monkeys work harder at a task -- and they were better at it, too, the U.S. government researchers found. Dr. Barry Richmond and colleagues at the National Institute of Mental Health used a new genetic technique to block the D2 gene. "The gene makes a receptor for a key brain messenger chemical, dopamine," Richmond said in a statement. Dopamine is a message-carrying chemical associated with rewards, movement and a variety of other important functions.

9. "The gene knockdown triggered a remarkable transformation in the simian work ethic. Like many of us, monkeys normally slack off initially in working toward a distant goal," he added. For their study, Richmond and colleagues used seven rhesus monkeys. They had to push a lever in response to visual cues on a projection screen, and got a drop of water as a reward. "They work more efficiently -- make fewer errors -- as they get closer to being rewarded. But without the dopamine receptor, they consistently stayed on-task and made few errors, because they could no longer learn to use visual cues to predict how their work was going to get them a reward."

10. Humans and monkeys both use this learning, which involves looking at how much work there is, visually, and deciding how long it will take to complete it. Monkeys and humans both tend to wait until the last possible minute to finish up the work, and become very adept at estimating how long they have. Molecular geneticist Edward Ginns created a DNA antisense agent that tricked brain cells into turning off their D2 receptors -- which are molecular doorways used by dopamine to get into cells. Antisense involves making a kind of mirror-image molecule that looks like a strand of DNA and works to block a gene's action.

11. Definitions Assumption: The act of taking for granted, or supposing a thing without proof; supposition; unwarrantable claim. ...

12. Assumption Good science demands that you try and account for your assumptions as best you can, but there’s no way of accounting for all of them, and they may not be true. For example, in this experiment, the authors assumed: The monkeys were/are representative of humans

13. Assumption Is it good to increase focus or work ethic? Why or why not? (This question is designed to make you aware of your assumptions!) Creativity? Different learning styles?

14. Definitions Hypothesis: A supposition; a proposition or principle which is supposed or taken for granted, in order to draw a conclusion or inference for proof of the point in question; something not proved, but assumed for the purpose of argument, or to account for a fact or an occurrence;

15. Hypothesis Good science demands that a hypothesis directs the experiment. In this case, based on the anatomical observation of dopamine fibers in the rhinal cortex and previous studies demonstrating the importance of this region to visually-related learning, the experimenters devised the following hypothesis:

16. Hypothesis Ifdopamine, acting through the D2 receptor, is critical for visual association, theneliminating dopamine will alter learning behavior in monkeys trained to do specific tasks.

17. Experiments TEST hypotheses An experiment should be designed to test the truthfulness of the hypothesis statement. This means that the data from the experiment will either support or not support the statement.

18. The results? Dopamine did in fact alter learning behavior in these monkeys, therefore, the hypothesis was correct! Now, would you like some D2-blocker before the next test?

19. Moving On Review Mitosis Introduce Meiosis Introduce DNA Replication Introduce DNA Recombination

20. The Plan Nucleus DNA Cell Gene Expression Individual Group or population

21. Comparing Mitosis and Meiosis One major goal of the study of genetics is to explain the apparently conflicting forces of biology: Heredity and Variation How do mitosis and meiosis influence these?

22. Mitosis—Review The cell cycle is composed of the Interphase (G1, S, G2) and Mitosis DNA is replicated (copied) during S phase Mitosis is the process of nuclear division that results in two genetically identical daughter cells from one progenitor cell The process of cell division following mitosis is called cytokinesis

23. Mitosis—Review The phases of mitosis are: Prophase Metaphase Anaphase Telophase

24. Mitosis—Review Mitosis is an important cellular process that drives both growth and development. Both the progenitor and the daughter cells are diploid (2n) Mitosis preserves the genetic composition of cells.

25. Meiosis

26. Meiosis Cell division that produces male and female gametes. Meiosis is characterized by two division processes that results in the formation of four gametes. Gametes arehaploid (n).

27. Meiosis Meiosis ensures genetic continuity from one generation from the next, but at the same time, ensures genetic variation among members of the same species. How?

28. Meiosis Meiosis results in the formation of haploid gametes. The haploid gametes represent half of the genetic material present in the parent (continuity). Crossing over or recombination of homologous regions of the chromosome shuffles the genetic material such that different gametes represent different inputs from the parent (variation).

29. Meiosis Two Phases: Meiosis I – called the “reduction” division because the number of centromeres, each representing one chromosome, is reduced by half during phase I. Meiosis II – called the “mitotic” or “equational” division because the number of centromeres remains the same.

30. Meiosis: Prophase I The most lengthy and complex step Divided into five subdivisions Remember, each occurs as a process with no clear borders between subdivisions.

31. Prophase I--Leptotene Chromosomes visible as long, thin threads Chromosomes begin to condense Homology search is thought to occur; this is where homologs begin to meet up prior to actual pairing.

32. Prophase I—Zygotene Homologues actively pair up (absolutely critical). Chromosomes progressively pair, side by side like a zipper. Homologous pairing is unique to meiosis…it does not occur during mitosis

33. Prophase I—Zygotene How do the homologues pair up?? Telomeres, the ends of the chromosomes, are thought to be important. Telomeres are attached to the nuclear membrane, and it is likely that telomeres from homologous pairs are close to each other to facilitate pairing.

34. Prophase I—Pachytene Chromosomes shorten and thicken further. Chromosomes pair more intimately, called synapsis Replicates are called sister chromatids (like mitosis), while chromatids from maternal vs. paternal members of a pair are called non-sister chromatids

35. Prophase I—Pachytene Thus, each structure is composed of FOUR chromatids and is called a tetrad. Crossing over or recombination, the exchange of genetic material between chromatids, occurs during the pachytene stage. This exchange produces genetic variability. The result is chromosomes that are a mosaic of both maternal and paternal contributions.

36. Prophase I—Diplotene It becomes apparent that each tetrad is composed of two pairs of sister chromatids, as each pair begins to separate. Chiasmas form in one or more areas where the chromatids remain in contact and represent areas where genetic exchange has taken place.

37. Prophase I—Diakinesis Chromosomes pull farther apart Non-sister chromatids remain loosely attached at chiasmata Chiasmata move towards the ends of the tetrads

38. Prophase I—Diakinesis The nuclear envelope and nucleolus break down The two centromeres of each tetrad attach to newly formed spindle fibers By the end, centromeres of each tetrad are lined up in the center of the cell

39. Metaphase I Terminal chiasmata appear to be the only factors holding non-sister chromatids together Centromeres are attached to spindle fibers and line up on the metaphase plate

40. Anaphase I Movement of one-half of each tetrad toward each pole The alignment (paternal vs. maternal) of tetrads is random, meaning that the resulting division will contain chromosomes from both sources.

41. Anaphase I This random direction of chromatids toward either pole contributes another source of variation from meiosis and is also called independent assortment. Remember this later in the semester when we discuss Mendelian genetics.

42. Anaphase I During anaphase, a single centromere holds each pair of sister chromatids together. It does not divide. One half of each pair (called a dyad) is pulled toward the pole of the cell in a process called disjunction. (Non-disjunction causes asymmetric arrangement of chromosomes [Down Syndrome/Trisomy 21])

43. Telophase I In most animals, a new nuclear membrane forms around the dyads. There is often a short interphase, but often the cell enters directly into phase two, or Meiosis II

45. Meiosis II Proceeds essentially like Mitosis During prophase II, each dyad is composed of one pair of sister chromatids joined by a single centromere. During metaphase II, the centromeres are lined up on the metaphase plate

46. Meiosis II During anaphase II, sister chromatids from each dyad are pulled in opposite directions and form monads. During telophase II, one member of each pair is present at each pole. Cytokinesis follows.

48. Meiosis II At the conclusion of meiosis II, each monad is a unique combination of maternal and paternal genetic input. The sources of variation are: 1. Recombination 2. Independent Assortment

49. Spermatogenesis vs. Oogenesis The genetic events (meiosis, crossing over, assortment, etc.) are common between the sexes. Cellular events differ considerably.

50. Spermatogenesis Takes place in the testes Spermatogonium: undifferentiated, diploid germ cell Primary spermatocyte: undergoes first meiotic division Secondary spermatocyte: undergoes second meiotic division to produce haploid spermatids