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11/14

11/14. Pick up Meiosis Notes Packet + diagram Test corrections today after school, tomorrow before school, and Friday before school with Mrs. Barker Lab Make-Ups today after school 3:00-3:30. Quiz FRIDAY! . Mitosis (Review)

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11/14

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  1. 11/14 • Pick up Meiosis Notes Packet + diagram • Test corrections today after school, tomorrow before school, and Friday before school with Mrs. Barker • Lab Make-Ups today after school 3:00-3:30. • Quiz FRIDAY!

  2. Mitosis (Review) – Division of a somatic cell that results in 2 genetically identical daughter cells • Cell division begins in Interphase when the chromosomes duplicate • Nucleus divides by means of Mitosis (PMAT) • Cytoplasm and organelles divide by Cytokinesis

  3. Chromosomes duplicate 2 new daughter cells identical to parent cell Parent cell • Daughter cells are genetically identical to parent cell – same kind and number of chromosomes • Mitosis occurs in somatic or body cells • Ex: liver, heart, skin, stomach • Every organism has its own unique number of chromosomes. Humans have 46. • Asexual reproduction for some species—ex: bacteria

  4. Meiosis – process by which the number of chromosomes is reduced to half the number in the daughter cells • A. Occurs in – sex organs • 1. Males – testes • 2. Females – ovaries • 3. Sex organs of other organisms – plants, animals, fungi

  5. B. Produces – sex cells or gametes • 1. Males – sperm • a. process called – spermatogenesis • b. meiosis produces - 4 sperm • 2. Females – egg or ova (singular = ovum) • a. process called – oogenesis • b. meiosis produces -1 egg • 3. egg and sperm are referred to as – gametes

  6. C. When does meiosis occur? • 1. Males – at puberty • 2. Females – before birth all eggs are produced • At birth, development of eggs stops; at puberty eggs mature

  7. D. Meiosis is also referred to as – chromosome reduction 1. Chromosomes number is always reduced by ½ a. total number of chromosomes – diploid #, 2N 1. all somatic cells – (body cells) diploid 2. humans 2N number - 46 b. half the number of chromosomes – haploid #, N 1. all sex cells –haploid 2. humans 1N number -23

  8. 2. This is necessary for any organism that reproduces sexually a. with meiosis……….. Fertilized egg – zygote N 23 Zygote develops into embryo and finally adult organism by mitosis 46 23 N 2N

  9. b. without meiosis ………… Fertilized egg – zygote 46 92 46

  10. Meiosis Mitosis

  11. E. Sex Chromosomes 1. Humans have 46 chromosomes, 23 pairs – 1 set from Mom and 1 from Dad 2. 22 pairs look alike – autosome chromosomes (not sex chromosomes) 3. 1 pair is the sex chromosomes – determines if you are male or female a. females: sex chromosomes are homologous – XX b. males: sex chromosomes are different – XY

  12. autosome

  13. F. Unique events of meiosis 1. homologous chromosomes pair up a. look alike b. code for the same traits c. one from each parent

  14. 2. homologous chromosomes exchange genes – crossing over a. produces new combination of genes b. source of genetic variation so offspring are not genetically identical to parents

  15. No crossing over – daughter cells are identical to parent cells Crossing over occurs –causes genetic variation (Daughter cells are NOT identical to parent cell)

  16. 11/15 • Reminder: Quiz Friday on Meiosis • Test Corrections – • today after school 3-3:30 • tomorrow morning 6:50-7:20 a.m. + enrichment • DLA today – get out a pencil • Ethan, Justin, Sophia – makeup test after school

  17. Meiosis Division 2 Division 1 Chromosomes duplicate Daughter cells have half as many chromosomes as parent cell Parent cell Crossing over would occur at this point Daughter cells

  18. Chromosome Problems Failure of the homologous chromosomes to separate normally during meiosis -- nondisjunction 1. missing a chromosome – monosomy (45 chromosomes) 2. having an extra chromosome – trisomy (47 chromosomes) 3. most embryos fail to survive, but some do

  19. a. short, round face, upper eyelids cover the inner part of the eye, mental retardation – trisomy 21 -- three #21 chromosomes (47 chromosomes) – Down Syndrome

  20. b. male with longer-than-average limbs, sterile – XXY Klinefelter’s Syndrome

  21. c. female with short stature, webbed neck, sterile – XO Turner’s Syndrome

  22. B. Parts of chromosomes break off and reattach in different ways, occurs in meiosis: deletion / translocation / duplication / inversion Deletion Duplication Inversion Translocation

  23. C. Detecting chromosome mutations: 1. Picture of individual’s chromosomes – karyotype 2. Amniotic fluid surrounding an embryo is removed for analysis (done 3½ to 4 months of pregnancy) –amniocentesis 3. Analysis of chorionic villi which grows between mother’s uterus and placenta (done 2 months of pregnancy – chorionic villi sampling (CVS)

  24. Comparing Mitosis and Meiosis

  25. Unique features of Meiosis Comparison of Meiosis and Mitosis

  26. Sex Cells

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