1 / 24

Notes: Karyotypes

Notes: Karyotypes. s. Human Chromosomes- what you know…. Humans have 46 chromosomes (diploid-2N) 2 of them are sex chromosomes (X and Y)  they determine what sex you are XX = female XY = male 44 of them are autosomes  they do not determine the sex of an individual.

hayfa-brewer
Download Presentation

Notes: Karyotypes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Notes: Karyotypes s

  2. Human Chromosomes- what you know… • Humans have 46 chromosomes (diploid-2N) • 2 of them are sex chromosomes (X and Y) they determine what sex you are • XX = female • XY = male • 44 of them are autosomes they do not determine the sex of an individual. Sex chromosomes

  3. How is a KARYOTYPE Made? • Collect sample: • Fetus: amniotic fluid collected during an amniocentesis or a piece of the placenta collected during a chorionic villi sampling test (CVS). • Newborn: white blood cells • Separate dividing & non-dividing cells using chemicals • Culture the dividing cells to get a lot of cells • Add chemical to stop cell division when chromosome is compacted • Lyse the cells • Stain the chromosomes (stain sticks to regions with a lot of “A” and “T” bases • Analyze!

  4. How is a KARYOTYPEAnalyzed? • Use computers to match the homologous pairs. • We will cut out the chromosomes from a chromosome spread then arrange them to match the banding patterns of the homologous pairs • Use banding patterns, size of chromosome, and position of centromere • This type of picture is called a KARYOTYPE

  5. Chromosome Spread

  6. Karyotype

  7. What does a Karyotype tell you? • Sex (male or female) • Irregular numbers of chromosomes • Any mutations in the chromosomes • Basically: all the chromosomes in a cell are displayed and can be examined for abnormalities

  8. Is this offspring a girl or boy? How do you know?

  9. Are there any abnormalities in this offspring?

  10. Chromosomal Disorders • Most of the time, the mechanisms that separate human chromosomes in meiosis work very well, but things can go wrong • The most common error: NONDISJUNCTION • The chromosomes fail to separate in Anaphase I or II • The result? Abnormal numbers of chromosomes in gametes.

  11. Nondisjunction Prefixes: dis = absence of / opposite of non = not Root Word: Junction = joining together • disjunction = the act of separating • nondisjunction = the act of not separating

  12. Metaphase I Figure 14-15 page 352 “Trisomy” = 3 copies of a chromosome Nondisjunction (after anaphase I) End of Meiosis—4 gametes produced

  13. Examples of Chromosomal Disorders • Down Syndrome (3 #21 chromosomes) • Klinefelter’sSyndrome (XXY) • Turner’s Syndrome (XO) • Triple X Syndrome (XXX)

  14. Examples of Nondisjunction resulting in Chromosomal Disorders • Down's Syndrome: 47 chromosomes with 3 #21 chromosomes. • Triple-X Syndrome: 47 chromosomes caused by 3 X chromosomes. • Klinefelter's Syndrome: 47 chromosomes caused by 2 X chromosomes and 1 Y chromosomes. • Turner's Syndrome: 45 chromosomes with 1 X chromosome (caused by the absence of one of the X chromosomes or a Y chromosome).

  15. Chromosomal Mutations • Chromosomal Mutations • Deletion • Duplication • Inversion • Translocation

  16. Chromosomal Mutation (change in number) • If an organism is born with the incorrect number of chromosomes • Ex: 47 human chromosomes instead of 46 • Result of nondisjunction

  17. Down Syndrome • 3 copies of chromosome #21 • 1 in 800 babies in the US is born with this disease • produces mild to severe mental retardation • May not live as long

  18. Klinefelter’s Syndrome • This is a sex chromosomal disorder associated with males. • Nondisjunction causes an extra X chromosome to be passed along during meiosis (XXY). • Resulting male cannot reproduce • Cases have been found in which individuals were (XXXY) or (XXXXY) • Decrease muscle mass and body hair

  19. Turner’s Syndrome • This is a sex chromosomal disorder associated with females. • Nondisjunction causes offspring to inherit only one X chromosome (genotype = XO). • Resulting female is sterile due to underdeveloped sex organs. • 1/2500 females

  20. Review question..Who determines the sex of a child? The mother or the father? THE FATHER!!!! Why?

  21. Why does the father determine the sex of the offspring??? • Mom is XX: she can donate either one X chromosome or the other X chromosome to the offspring (mom can only donate an X) • Dad is XY: he can donate either an X chromosome or a Y chromosomes. • If the offspring receives an X from dad, it is female • If the offspring receives a Y from dad, it is male

More Related