Chromosomes

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Jtrosmarin
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133474
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Chromosomes
Updated:
2012-02-07 10:27:56
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Chromosomes Human Health
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  1. Genes
    • •Coded information (“recipe”)
    • for making proteins

    •Genes are on our chromosomes
  2. Chromosomes: A review
    • Humans have 46 chromosomes or 23 pairs within
    • a cell’s nucleus
    • –Chromosome pairs 1 through 22 control traits that do not relate to gender of an individual.
    • –The 23rd pair are the sex chromosomes that contain the genes that do control gender.
    • •So most of the cells of our body have 23 pairs of chromosomes, or 46 total.
    • •Only sperm and eggs have 1 of each pair or a
    • total of 23 chromosomes.
  3. Our Cells
    • •Egg and Sperm
    • –Gametes
    • –For reproduction

    • •All other cells
    • –Have 23 pairs of
    • chromosomes
  4. Cells other than egg and sperm
    • •Must make new cells for:
    • –Repair
    • –Growth
    • •Do this by process of Mitosis
    • (Duplication)
    • •Creates two identical daughter cells
  5. Sperm and Eggs
    • •One of each chromosome (not pair)
    • •Fuse together at fertilization
    • •Produced by process of meiosis
  6. Meiosis
    •Produces cells with half the normal number of chromosomes
  7. Fertilization
    • •Egg and sperm fuse
    • •Creates one cell with normal number of chromosomes
    • •Cells replicate to form embryo
  8. How come we are different from siblings?
    Crossing Over
    when the chromosomes line up in egg and sperm to separate they exchange some genes.
  9. How come we are different from siblings?
    Independent assortment
    Chromosomes line up or "shuffle" randomly during Meiosis. •2^23, or 8 million possible assortments of chromosomes !
  10. How come we are different from siblings?
    Random fertilization
    • Ovum has 8 million possible chromosome combinations, so does the sperm cell.
    • 8 million x 8 million = 64 trillion
    • possible combinations in EACH AND EVERY zygote
  11. What is a karyotype?
    •Visual (snap shot) of one’s chromosomes
  12. Sex Chromosomes
    • •Normal Female: XX
    • •Normal Male: XY
  13. Mitosis
    • •Growth and repair of cells
    • •Occurs in body cells
    • •1 division
    • •Results in 2 daughter cells genetically identical cells (46chromosomes)
  14. Meiosis
    • •Formation of gametes
    • •Occurs in sex cells
    • •2 divisions
    • •Results in 4 daughter genetically different cells (23
    • chromosomes)
  15. Changes in chromosome number
    • •Nondisjunction occurs when both copies of a chromosome go into the same gamete (i.e. they fail
    • to separate).
    • •Results of nondisjunction:
    • –Monosomy: cell has only 1 copy of a chromosome
    • e.g. Turner syndrome (only one X chromosome)
    • –Trisomy: cell has 3 copies of a chromosome
    • e.g. Down syndrome (3 copies of chromosome 21)
  16. Chromosome number
    • •Chromosomes occur in pairs (1 from each parent)
    • •If missing one, usually fatal (except can have just one X)
    • •If have more than 2 , usually fatal (except the smaller pairs of chromosomes ex. #21, or the sex chromosomes)
  17. Down Syndrome (Trisomy 21)
    • •Extra copy of chromosome 21 from ova (advanced maternal age)
    • •Short stature, eye shape, short fingers, rounded head, palm crease, mental retardation
  18. Down Syndrome
    • •One of the most common causes of mental retardation
    • •Up to half of people with DS have heart defects
    • •Up to 1/3 of people with DS have digestive disorders
    • •Many have respiratory and immune system defects and increased chance for leukemia
    • •Average life expectancy: 49 years of age
  19. Prenatal Detection
    • •Screening blood tests in all pregnant womencan alert to increased chance of fetal down syndrome
    • •Amniocentesis with karyotyping can detect Down Syndrome in utero
  20. Changes in sex chromosome number
    • •Poly-X female (XXX, XXXX)
    • –XXX tends to be tall and thin but not usually retarded
    • –XXXX are severely retarded
    • •Jacobs syndrome
    • (XYY) – tall, persistent acne, speech and reading problems
  21. Changes in chromosome number
    • Turner Syndrome (X) (females)
    • •Immature sex organs, infertility, webbed neck, short stature, normal intelligence
  22. Klinefelter Syndrome
    • •1 in 650 males have XXY (instead of XY)
    • •Often no signs •Sometimes becomes evident at puberty
    • •Some characteristics:
    • –Long legs, shorter trunk, less body/facial hair, enlarged teeth, enlarged breasts –Infertile
    • –Symptoms vary from mild to severe
    • –Can be given testosterone supplements
  23. Changes in chromosome structure
    • •Chromosomes can be damaged, break, and not
    • rejoin the way they should
    • •Causes:
    • –Radiation (remember Cherynobol & thyroid cancer)
    • –Chemicals (ex. Cigarettes & lung cancer)
    • –Viruses (sexually transmitted HPV and ovarian cancer)
  24. Changes in chromosome structure
    • •Deletions: loss of a piece of the chromosome (e.g. Williams syndrome)
    • •Translocations: movement of chromosome segments from one chromosome to different chromosome (Alagille
    • syndrome)
    • •Duplications: presence of a chromosome segment more than once in the same chromosome
    • •Inversions: a segment of a chromosome is inverted 180 degrees
  25. Cri du Chat Syndrome
    • •Deletion on chromosome 5- can be detected by Chorionic villus sampling
    • •Causes varying levels of mental retardation
    • •Characteristic “cry”
    • –Abnormal larynx development
    • •Scoliosis, muscle tone issues
    • •Facial/skull abnormalities
  26. Translocations
    • •Alagille Syndrome
    • –Translocation between #2 & #20
    • –Characteristic facial features: prominent forehead, small chin)
    • –Abnormalities in eyes, internal organs (liver)
    • –Can be mild or severe
  27. Translocations
    • •Some kinds of cancer –
    • –22 & 9
    • myelogenous leukemia

    • –8 & 14
    • Burkett Lymphoma

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