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Class Topics

This class covers topics related to biology, including cell division, chromosomes, and genetic material. Students will take a chapter 5 test and begin learning about cell division in chapter 6.

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Class Topics

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  1. All chapter 5 corrections are to be handed in before the bell rings Chapter 5 Test Begin Chapter 6 “I find the harder I work, the more luck I seem to have.” Thomas Jefferson To assess knowledge of chapter 5 and begin learning about cell division. Title: Biology 12/6/06 Class Topics Objectives: Friday, January 3, 20201:50 AM

  2. Class Assignments What By When • Chapter 5 Test 12/6/06 • Read 118-129 12/8/06 • W.S. 6.1 12/8/06 • Due this class period • Due next class period • Due in the future

  3. Grade Sheet 1A – SR p. 61 - 5 pts Measurement W.S. – 10 pts 3A SR p. 42 – 6 pts 4A – SR p. 47 – 5 pts 2A – Measurement W.S. – 10 pts SR p. 80 – 5 pts

  4. Posttest Activities • Read 118-129

  5. Chromosomes • Made from DNA • Genetic material that directs activities and determines characteristics • Formed from chromatin • Right before mitosis • Chromatin coils up into rods

  6. Eukaryotic Cell Reproduction(Mitosis) • Each chromosome (at this point) is made up of 2 identicalchromatids • Joined strands of identical duplicated genetic material • Joined at centromere • Chromatids separate and each cell has identical information • Formed in S phase of cell cycle Chromosome Number in Various Organisms & Chromosome Structure From: http://www.rothamsted.bbsrc.ac.uk/ notebook/courses/guide/chromo.htm

  7. From: http://www.accessexcellence.org/RC/VL/GG/nucleosome.html

  8. Sets of chromosomes • Each human somatic cell has 23 pairs of chromosomes (46 total) • Homologous chromosomes • Each pair is called homologous • Similar in size, shape and genetic content • Not identical! • One from each parent

  9. Sets of chromosomes • Somatic cells • Diploid (2n) • 2 sets of chromosomes (46 total) • Homologous pairs • Gametes • Haploid (n) • 1 set of chromosomes (23 total) • Sperm and egg • If an organism has haploid number ___ of chromosomes, how many are in a diploid cell? • Fertilization • Two haploid gametes join to form a zygote (2n) • Fertilized egg

  10. Numbers of chromosomes Karyotype • Table 1 (p. 121)

  11. Chromosomes • 23 homologous pairs • 22 pairs of autosomes (44 total) • Numbered chromosomes • 1 pair of sex chromosomes (2 total) • Contain genes to determine gender???? • X chromosome – needed, many genes • Y chromosome – genes used to determine male gender • Male XY • Female XX • Father determines gender of child • Sperm contains X or Y chromosome “Geographer of the Male Genome”

  12. Changes in chromosome number • Monosomy • Having 1 less chromosome (45) • Autosomes = lethal • Sex = XO – Turner syndrome • YO - lethal • Trisomy • Having 1 more chromosome (47) • Abnormalities occur • Trisomy 21 = Down syndrome • Caused by nondisjunction • failure of chromosomes to separate

  13. Down Syndrome • Occurs most often in “older” mothers • +37 years 1 in 290 births • +45 years 1 in 46 births • Characteristics • Short stature, round face, “slanted eyes”, varying degrees of mental capacity • Prenatal testing • Amniocentesis • Chorionic villi testing

  14. Mutation(Handout) • Changes in chromosome structure • Deletion • Cri du chat syndrome • 5p deletion • Translocation • 14-21 • Another cause of Down Syndrome From: http://www.criduchat.asn.au/criduchat/what.htm#Diagram%201

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