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Announcements

Announcements. Part of Lab in Brooks 101 computer lab next week Bring FlyLab and computer disc (available in bookstore) Change in syllabus: exams are on Th. (9-9pm) and Fri. (9-5pm) Read chapters 2, 3 carefully

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Announcements

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  1. Announcements • Part of Lab in Brooks 101 computer lab next week Bring FlyLab and computer disc (available in bookstore) • Change in syllabus: exams are on Th. (9-9pm) and Fri. (9-5pm) • Read chapters 2, 3 carefully • Continue reading “Monk in the garden”; discuss paper due date; check out related web pages: www.netspace.org/MendelWeb/ and www.monkinthe garden.com • Quiz this Friday, August 30, on lectures 1 and 2. • Homework this week: Ch.2, problems 2, 10, 13, 14, 19 (NOT turned in) • When/how to print powerpoint slides

  2. Answers to pre-test questions What is a gene? unit of heredity, residing at a specific point on a chromosome; a length of DNA that specifies a product What is a chromosome? condensed, linear DNA and protein, containing genes and intervening sequences - genes are organized into chromosomes Name one well-known geneticist: GregorMendel Who won the 2001 Nobel Prize in Medicine? Lee Hartwell, Paul Nurse, Tim Hunt What was their scientific contribution? Discovery of genes and regulatory molecules that control the cell cycle What does it mean to be diploid? 2n, having 2 copies of each chromosome What would happen without meiosis? Polyploid embryos, no functional gametes, no genetic variation Where does transcription occur in a cell? nucleus What are 2 applications of genetics you are interested in learning more about? many suggested cloning, gene therapy, stem cells, genetically modified foods

  3. Review of last lecture • What does it mean to study genetics? understanding how traits are transmitted and sources of genetic variation • Brief history of different ideas scientists have had re. transmission of traits; one key expt. What is an analagous illustration to Weismann’s mouse tail-cutting expt. that disproves Lamark’s hypothesis: particles migrate from all cell to the sex cells to transmit characteristics?

  4. Outline of Lecture 2 I. Basic concepts that underlie the study of genetics: DNA, genes, chromosomes II. How do scientists investigate genetics? III. Genetics and society IV. Very brief overview of cell structure - see pp. 17-21 and intro textbook if needed V. Homologous chromosomes and Mitosis

  5. I. Basic concepts • Gene: unit of heredity, residing at a specific point on a chromosome; a length of DNA that specifies a product • Chromosome: condensed, linear DNA and protein, containing genes and intervening sequences • DNA: the genetic material in all living organisms; in eukaryotes, located in the nucleus on chromosomes

  6. Biological flow of information (central dogma) DNA RNA Protein Trait

  7. How many chromosomes does an organism have? • Most eukaryote species have a specific number of chromosomes in each cell • In somatic cells (all cells but sperm and egg), this number is the diploid number, 2n ex. Humans have diploid # of 46. • This is 2 copies of each type of chromosome (1 from mom and 1 from dad); the haploid # is 23.

  8. How are chromosomes duplicated during cell division? • When do somatic cells divide? ie. Why do cells divide? • What is this cell division called? MITOSIS (2n to 2n) • What happens if chromosomes are not duplicated correctly? ex. Cri-du-Chat syndrome Small part of chromosome 5 is lost: results in heart problems, mental retardation, and other problems

  9. Cri-du-chat syndrome karyotype

  10. Meiosis- a special cell division to make gametes (sperm and egg) Why would a “regular” mitosis be a problem in making gametes? + If 2n 2n then 4n sperm, egg embryo • Meiotic cell division generates cells with one-half the genetic material (2n to 1n) - a reduction in chromosome number • Source of genetic variation - more on this next time

  11. Multiple choice The organization of genetic material is as follows: • Chromosomes are located on genes in the nucleus • Genes are located on chromosomes in the nucleus • Genes are located on chromosomes in the cytoplasm • Chromosomes are located on genes in ribosomes

  12. II. How do we investigate genetics? • Transmission genetics - how are traits inherited from parents to offspring? examine patterns of inheritance of traits • Molecular genetics - what is the structure and function of genes at the molecular level? has led to DNA biotechnology applications • Population genetics - how do gene frequencies change (evolve) in populations?

  13. Basic vs. Applied Genetics • Basic research: knowledge for its own sake • ex. Human genome project; essential for applied research • Applied research: seeks to improve the well-being of human or society • ex. Agriculture: selective breeding, genetically modified foods • Medicine: new methods to diagnose and treat genetic disorders

  14. III. Genetics and Society Late 1800’s: First attempt to apply genetic knowledge directly for improvement of human existence • based on Charles Darwin’s theory of natural selection- “survival of the fittest” • “eugenics” was favored by his cousin, Francis Galton: ` one can artificially select human characteristics by controlling human matings **Positive vs. negative eugenics

  15. Genetics and Society, cont. Historically: eugenics taken to the extreme- Nazi Germany 1930’s What about in USA??? 1907- Indiana passed a law to require sterilization of those people considered genetically inferior Over half of the states passed such laws! These policies were flawed both ethically and by NOT understanding the genetic basis of various characteristics

  16. Determination of phenotype Are “superior” or “inferior” traits totally under genetic control? NO! • Genotype - provides the blueprint • Environment - internal or external influences • Developmental noise - random events during embryonic development

  17. Should we ever apply genetic knowledge for the improvement of human existence? Euphenics: medical or genetic intervention designed to reduce the impact of defective genotypes on people ex. Insulin treatment • Advances in agriculture: • plants - increased yields, increased resistance, hybrid production, selection of genetic variants (for better nutrition) • livestock - higher quality meat; larger size and number of eggs

  18. IV. Cell Structure

  19. V. Homologous chromosomes and mitosis • Recall that somatic cells contain an identical # of chromosomes, called the diploid number, 2n. (2n= 46 for humans) • Nearly all chromosomes exist in pairs; the members of each pair • are called homologous chromosomes • ex. Each cell has 2 copies of chromosome 1, one from • mom and one from dad. These 2 copies are called • homologous chromosomes. • While homologous chromosomes have much genetic similarity, • they are not necessarily identical. Different forms of the • same gene, alleles, may exist.

  20. Karyotypes of human chromosomes

  21. Concept of alleles Example: cystic fibrosis gene is CFTR, a transmembrane conductance regulator. When mutated, epithelial cells have irregular salt ion conductance; this results in excesive salty secretions and thick mucous build- up in lungs. We all have the CFTR gene: Most of us have 2 wt (normal) copies of the gene. Some of us have 1 wt copy and 1 mutated copy - carrier. Few of us have 2 mutated copies - CF disease. The mutated copy and the wt copy are two alleles of the CFTR gene.

  22. Mitosis is one part of the “cell cycle” Many cells alternate between dividing and “resting” or not dividing Gap 1; metabolic activity and cell growth G0(resting phase) Mitosis DNA synthesis 1 hour of 16 hour cell cycle Gap 2; metabolic activity and cell growth

  23. Why and when is mitosis important? (why should you care about cell division) • How does a one-celled embryo grow into a multi-cellular organism? • When do cells need to be made in adults? ex. skin cells in humans are continuously being sloughed off and replaced - as many as 100 billion (1011) cells are lost daily • In abnormal situations, cells may divide “out of control” - cancer

  24. Mitosis - the mechanics Two steps: nuclear division (karyokinesis) cytoplasmic division (cytokinesis) Four phases: prophase metaphase anaphase telophase

  25. Prophase Metaphase Anaphase • Kinetochore microtubules attach to chromosomes • Chromosomes move to midline/metaphase plate • Centrosomes migrate • Spindle fibers form • Chromatin condenses • Links break • Daughter chr. • move to poles Telophase Cytokinesis • Chr. reach poles and decondense • Nuclear envelope reforms • Spindle fibers disappear

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