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Karyotypes

Karyotypes. Karyotype =. A display (picture) of all the chromosomes in the nucleus of a cell. How do you make a karyotype?. 1. Cell cycle is stopped in mitosis Why? So you can see the chromosomes 2. Put cells on microscope slide 3. Stain cells so the chromosomes can be seen

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Karyotypes

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  1. Karyotypes

  2. Karyotype = • A display (picture) of all the chromosomes in the nucleus of a cell.

  3. How do you make a karyotype? • 1. Cell cycle is stopped in mitosis • Why? • So you can see the chromosomes • 2. Put cells on microscope slide • 3. Stain cells so the chromosomes can be seen • 4. Take a picture of what is seen under the microscope • 5. Enlarge picture

  4. What do Doctors do with karyotypes? • 1. Cut out chromosomes • 2. Pair up homologous chromosomes • according to size starting with the largest, position of centromere and banding pattern • 3. Glue them down with their homologous partner

  5. Enlarged picture of chromosomes in prophase Completed karyotype

  6. Remember... • Normal humans have 2 of each chromosome • No more -- no less

  7. Sex chromosomes • the X & Y • Always the last set of chromosomes • Males = XY • Females = XX

  8. Autosomes - • All chromosomes except for the X & Y (sex chromosomes) • Pairs 1-22

  9. What can a Dr. determine from a karyotype?

  10. Sex of a person • determined by the 23rd pair of chromosomes (in humans) • Females have 2 “large” X chromosomes • Chromosomes will be the same size • Males have 1 “large” X and a smaller y chromosome • Chromosomes will not be the same size

  11. What else can a doctor determine? • The presence of a chromosomal number defect …

  12. Disjunction Normal separation of Chromosomes and Chromatids during Meiosis I and Meiosis II (Anaphase I & II)

  13. Normal Karyotypes Has 46 chromosomes for humans Arranged in 23 pairs

  14. Nondisjunction- failure to separate

  15. What does nondisjunction cause? Missing Chromosomes – Monomy Embryo/Fetus will not survive Means 45 chromosomes Exception is this can occur on 23rd chromosome pair Extra Chromosomes – Trisomy Means 47 chromosomes • Down Syndrome (Trisomy 21) • Patau Syndrome (Trisomy 13) • Klinefelter’s Syndrome (XXY) • Turner’s Syndrome (X-) • XYY Syndrome • And many more………….

  16. 47, XX or XY, +13 • Serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months. • Patau Syndrome

  17. Cleft Palate

  18. Klinefelter’s Syndrome

  19. Symptoms of Klinefelters • Sterile male • Testes abnormally small • Later in life feminine contours may develop

  20. Characteristics of Cri-du-chat • Has only 1 chromosome at locus 5 • Mentally retarded • Small head

  21. Characteristcs of Cri-du-chat • Unusual facial features • Cry sounds like a cat meowing

  22. Characteristics of Turner Syndrome • Only 1 X no y • Female • Sex organs and secondary sex characteristics do not develop

  23. Characteristics of Turner Syndrome • Sterile • Short of stature • Mentally “normal”

  24. Characteristics of Down Syndrome • Has 3 chromosomes at locus 21 • Characteristic facial features • Mentally retarded • short

  25. Characteristics of Down Syndrome • Heart defects • Webbed fingers • Generally do not live to be much older than 30

  26. Amniocentesis

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