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Essential Questions…

In this lab, students will create and analyze a karyotype of cells from a fetus to count chromosomes and determine the sex of the fetus. The lab includes directions, questions, and a karyotyping worksheet.

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Essential Questions…

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  1. Essential Questions… • What is a karyotype? • What can it help you determine? • What does a karyotype of a human look like?

  2. Karyotyping Lab 50 points - 40 points for correct karyotype - 10 points questions Due tomorrow but you could finish in class

  3. Objective • In this lab, you will create and analyze a karyotype of cells from a fetus to count chromosomes & determine the sex of the fetus. • Get into groups and collect materials • Karyotyping directions • Karyotyping questions • Karyotyping blank • Karyotyping spread • Scissors • Glue

  4. What is a Karyotype? • A karyotype is a diagram that shows a cell’s chromosomes arranged in order from largest to smallest. • A karyotype is made from a photomicrograph (photo taken through a microscope) of the chromosomes from a cell in some phase of meiosis. • The photographic images of the chromosomes are cut out and arranged in homologous pairs by their size and shape. • The karyotype can be analyzed to determine the sex of the individual and whether there are any chromosomal abnormalities. • For example, the karyotype of a female shows two X chromosomes, and the karyotype of a male shows an X chromosome and a Y chromosome.

  5. Directions • In groups of two, read through and follow directions. • Create your karyotype, analyze it, and answer the associated questions. • You will turn in: • Karyotype • Answers to questions • One worksheet per group of two with both partners’ name on it. • WARNING: THE PIECES GET LOST EASILY AND YOU HAVE TO HAVE ALL OF THEM TO COMPLETE THE ASSIGNMENT. TAKE CARE OF THEM.

  6. Determining Sex of a Child AUTOSOMES = contain the genes for regular traits • Look at the directions page. Outline the following chromosomes. SEX CHROMSOMES = contain the genes that determine gender. XX = female, XY = male

  7. Chromosome Abnormalities

  8. A Common Abnormality…Down Syndrome • Trisomy is an abnormality in which a cell has an extra chromosome, or section of a chromosome. This means that the cell contains 47 chromosomes instead of 46. Down syndrome, or trisomy 21, is a chromosomal abnormality that results from having an extra number 21 chromosome. This extra chromosome means too many genes and developmental problems generally result. • A variety of developmental problems from functional (able to drive, live alone) to seriously debilitating (mental retardation that requires 24-hr monitoring) can result. • Odds: 1:1000 births

  9. Other Chromosome Anomalies Trisomy X • Three ‘x’ chromosomes • Odds: 1:1000 females

  10. Turner’s Syndrome • Generally only female with only 1 ‘x’ chromosome. • Odds: 1:2500 females

  11. More • Klinefelter syndrome • XXY (1:500-1000 males) • XYY Syndrome • XYY (1:1000 males) • Cri du chat • Missing part of #5 (1:50,000) • Others can occur with the other chromosomes as well.

  12. Chromosomal Abnormalities How Do They Happen? • Chromosomal abnormalities often result from nondisjunction, the failure of chromosomes to separate properly during meiosis. • Nondisjunction results in cells that have too many or too few chromosomes.

  13. What’s the Problem? 47 Chromosomes in gamete

  14. Procedure:Make sure to write the letter of the version of your chromosome spread on your karyotype spread! • READ the directions page. This is a class set so please do not take or write on this. • CUT OUT EACH CHROMOSOME from the chromosome spread in Figure 2. Be sure to leave a slight margin around each chromosome. • ARRANGE THEM IN HOMOLOGOUS PAIRS. The members of each pair will be the same length, have similar banding, and will have the centromere in the same location. Use the banding patterns and compare them to the key. Arrange the pairs according to their length, from largest to smallest. • TAPE OR GLUE each homologous pair to a human karyotyping form positioning the centromeres on the same lines. Place the pairs in order, with the longest pair at position 1, the shortest pair at position 22, and the sex chromosomes at position 23. • CLEAN UP your materials before leaving the lab. • ANALYZE the karyotype to determine the sex of the individual and whether or not the individual will have Down syndrome. • ANSWER THE QUESTIONS in pairs on a separate sheet of paper.

  15. Possible Outcomes Answer all 10 questions on a separate sheet of paper. 10. Use the green “The Living World” book, pg. 187, to draw non-disjunction. DUE TOMORROW 50pts. • Normal Male • XY • Normal Female • XX • Down’s Syndrome • 3x #21 (1:1000 births) • Trisomy X • XXX (1:1000 females) • Turner’s syndrome • X (1:2500 females) • Klinefelter syndrome • XXY (1:500-1000 males) • XYY Syndrome • XYY (1:1000 males) • Cri du chat • Missing part of #5 (1:50,000)

  16. Questions What is your karyotype spread letter? ___________ • How many chromosomes do you have in your karyotype? • What is a HOMOLOGOUS PAIR and how many does your karyotype have? • What are AUTOMSOMES and how many are present? • What are SEX CHROMOSOMES and how many does your karyotype have? • What is a chromatid and how many chromatid does your karyotype have? • What is the haploid number for this organism? n = ____ • What is the diploid number of this organism? 2n = ____ • Does your karyotype reveal an abnormality? (yes or No). IF YES, describe it. • What sex is the organism? • In your biology books, non-disjunction is diagramed. Copy this diagram to explain how chromosomal abnormalities might occur in organisms.

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