In this activity, you will create a karyotype from a page of mixed chromosomes. Karyotypes are created by matching homologous pairs and numbering them from largest to smallest. Abnormalities, such as extra or deleted chromosomes can then be diagnosed. Pictured chromosomes will be used for this model rather than real chromosomes, but the process is the same for real chromosomes extracted from cell or fetal samples.
Two karyotypes will be created, the first represents a normal human karyotype of a male or a female, the second represents an abnormal karyotype. You will then compare and diagnose the abnormality present in the patient of the second karyotype.
Examine the page marked "normal" (You will receive either Normal Girl and Normal Boy sets) These chromosomes are actually enlarged photographs of what is seen through a microscope. Note that the sex chromosomes have been labeled for you as either X or Y chromosomes. They have been marked this way to indicate these are the sex chromosomes. Cut out each chromosome with scissors, to make it go faster, cut them out as squares rather than trying to cut around the margin of each chromosome.
Prepare a karyotype of these chromosomes. A karyotype is a pattern or picture of chromosomes from one cell grouped into pairs and organized by size.
--Pair up each of the chromosomes with its homologous pair, use the size and markings on the chromosomes to determine pairs. Temporarily put the two unshaded chromosomes aside.
--On a blank paper, arrange the chromosome pairs from largest to smallest and number them. You numbers should range from 1(largest) to 22(smallest). Put the sex chromosomes last, this is pair #23. Glue or tape the chromosomes to the paper in the correct order.
Sex chromosomes determine the sex of the individual. A female develops when the sex chromosomes match--XX . A male develops if the two sex chromosomes are unmatched--XY. (These chromosomes are unshaded on your karyotype)
1. How many total chromosomes are present in this karyotype? _____________
2. How many chromosomes are present in each cell of this human? _____________
3. Does your karyotype represent a male of a female? ________________
4. Chromosomes that are NOT sex chromosomes are called autosomes. How many total autosomes are present in your normal karyotype? ______________
Body cells are called somatic cells. Somatic cells include the skin, liver, muscle, stomach and other bodily cells. The karyotype you prepared is from a somatic human cell. The term diploid chromosome number refers to the number of chromosomes in a somatic cell. The diploid number varies from species to species, however it does not differ from somatic cell to somatic cell within the same organism. To find your diploid number, simply count the number of chromosomes in your karyotype.
The diploid chromosome number is also called the 2n number.
4. What is the diploid chromosome number for your karyotype? _____
5. What is the 2n chromosome number for your karyotype? ____
The HAPLOID CHROMOSOME NUMBER refers to the number of chromosomes in an organisms sex cells. Sperm in males, eggs in females. The haploid number, or 1n number is always -half- that of the diploid number.
6. What would the haploid chromosome number for your karyotype be? ____
--Prepare a second karyotype as you did the first. In this karyotype, you will discover an abnormality in the chromosome number. Finding incorrect chromosomes numbers in human somatic cells of an unborn baby alerts doctors to the fact that their child is abnormal and will be born with birth defects.
*If the unborn has an extra number 13 chromosome, it it born with Patau syndrome. An extra chromosome 18 results in Edward syndrome. An extra chromosome number 21 results in Down Syndrome. A missing sex chromosome results in an X0 offspring who has Turner's syndrome. An extra X chromosome results in Klinefelters syndrome (XXY).
7. How many chromosomes are present in the abnormal karyotype: ________
8. What is the diploid chromosome number for this karyotype: _________
9. Which chromosome pair is abnormal? __________
10. What syndrome does this unborn have? ____________
11. What sex will the unborn child be? _____
12. Define the following terms:
Diploid chromosome number
14. Describe two types of information that can be gained about a child before it is born through a karyotype.