CTYOGENETIC LAB - KARYOTYPING
There are several genetic disorders that involve visible structural changes in the
chromosomes. The objective of this lab will be to:
1. Learn and practice one of the methods used to classify chromosomes based
on their length and centromere location;
2. Determine at least one normal and one abnormal human karyotype;
3. Connect chromosome abnormalities to known genetic abnormalities.
PROCEDURE:
1. Obtain a set of normal male or female chromosomes.
2. Match the chromosomes with their homologous mates. (The corresponding
mate should be of the same size, and have the same centromere location.)
Number the chromosome pairs with the number one chromosome pair being
the longest. You need to be very systematic.
3. Once you have sorted the chromosomes into homologous pairs, affix them to
the human karyotype form provided and fill in the blanks indicated. (Use the
normal human karyotype form example to see how your final karyotype
should look.)
4. Select a second set of chromosomes.
5. Using the procedures in step #2 and #3, determine whether this is an
abnormal karyotype by using the Chromosome Analysis Key below. Keep in
mind there might be some slight variations. The key will help guide you.
6. On your second karyotype form, briefly describe the chromosome
abnormality in the karyotype you analyzed. Be sure to include the type
of abnormality, the total number of chromosomes in the karyotype, the
specific chromosome involved, the gender of the karyotype, and the
reason for the gender on your form.
7. For each abnormal karyotype, answer the following question on the back
of the form.
8. Using your knowledge of meiosis discuss how this chromosome
abnormality could have occurred. After comparing disorders, which of
the chromosome disorders seems to be the most damaging? Least?
Explain giving an example. Why do you think that there was only one
monosomy example?
9. Karyotyping can be used as a prenatal screening tool. Is a baby
guaranteed to be free from genetic disorders if the chromosome
configuration appears normal? Explain.
SIMPLE KEY FOR DIAGNOSING CHROMOSOME ABNORMALITIES
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1A-46 chromosomes in karyotype...................................................... GO TO
STATEMENT 3
1B-Not 46 chromosomes in karyotype............................................... GO TO
STATEMENT 2
2A-47 chromosomes in karyotype (3 of one chromosome).. Trisomy
condition
2B-One chromosome missing from pair.......................... Monosomy condition
3A-All chromosomes are matched with its homologue without obvious
missing pieces or additions......................................Possible Normal individual
3B-Homologous pairs are not identical in size........................... GO TO
STATEMENT 4
4A-There are additions pieces attached to a chromosome..............
Translocation
4B-There are missing pieces in a chromosome.................................. Deletion
Materials for Lab
 Human Karyotype Forms
 Normal Human Karyotypes : the following karyotypes will be available for
you to analyze. Only the normal ones will be labeled.
 Normal Female 46, XX karyotype
 Normal Male 46, XY karyotype
 Abnormal Human Karyotypes
 TRISOMY
 Trisomy 13 (47,XX,+13) – Patau Syndrome – Most die within first
month of birth
 Trisomy 16 (47,X,+16) – most common abnormality – never survives
past first trimester
 Trisomy 18 (47, XY,+18) – Edwards Syndrome – less than 10% survive
first year
 Trisomy 21 (47,XY,+21) – Downs Syndrome –average live expectancy
16.5 years
 Trisomy XYY (47,XYY) – Jacobs Syndrome – tall males with limited
mental capacity
 Trisomy XXY (47,XXY) - Klinefelter’s Syndrome – tall males, sterile
 MONOSOMY
 Monosomy X (45,X) – Turner’s Syndrome – short females, sterile
 DELETIONS
 Cri-du-chat 46XX or 46XY with Chromosome #5 upper arm deleted