Name: ________________________________ Date:____________ Group:_____ Period:______
Human Karyotyping Lab
Background:
Occasionally chromosomal material is lost or rearranged during the formation of gametes or during cell division of
the early embryo. Such changes, primarily the result of nondisjunction or translocation, are so severe that the
pregnancy ends in miscarriage – or fertilization does not occur at all. It is estimated that one in 156 live births have
some kind of chromosomal abnormality.
Some of the abnormalities associated with chromosome structure and number can be detected by a test called a
karyotype. A karyotype can show prospective parents whether they have certain abnormalities that could be
passed on to their offspring, or it may be used to learn the cause of a child’s disability. Karyotypes can also reveal
the gender of a fetus or test for certain defects through examination of cells from uterine fluid – a procedure called
amniocentesis – or through sampling of placental membranes. Over 400,000 karyotype analyses are performed
each year in the U.S. and Canada.
To create a karyotype, chromosomes from a cell are stained and photographed. The photograph is enlarged and cut
up into individual chromosomes. The homologous pairs are identified and arranged in order by size (with the
exception of the sex chromosomes; these appear last). These tests are typically done on a sample of blood, although
any body cell could be used. The cell must be undergoing mitosis – preferably in metaphase – so that the
chromosomes are replicated, condensed, and visible under a microscope.
A normal human karyotype will have 46 total chromosomes, 23 pairs. The last pair, the 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. An abnormal karyotype may have only 45 or 47+ chromosomes,
depending on the disorder. Numerical chromosomal abnormalities result from an incorrect distribution of
chromosomes into the gametes during meiosis. This can happen when homologous chromosomes (maternal and
paternal chromosome copies) fail to separate during meiosis I, or when sister chromatids (duplicate chromosome
copies joind at the centromere) fail to separate during meiosis II. This lack of chromosome separation is called
nondisjunction. It results in some gametes have two copies of a particular chromosome and some gametes without
any copies (see Figure below).
Purpose: The purpose of this laboratory experience is:
-understand what a karyotype is and how it is performed.
-understand reason for performing a karyotype.
-to determine what genetic defect is present in a chromosome sample.
-to investigate a variety of genetic disorders that commonly occur and are studied in biology classes.
Materials: The following materials are needed to perform this laboratory experience:
-2 sets of chromosomes
-2 magnetic boards
-Chromosome Key
-Chromosomal Abnormalities Key
Procedure:
1. Using the materials, you will complete TWO different karyotypes provided ONE AT A TIME. One will be
normal & one will be abnormal.
2. On the data sheet mark which set of chromosomes you will be using.
3. Record the total number of chromosomes in the set.
4. Compare the chromosomes in the bag to the Chromosome Key and find its’ EXACT match. Place the
chromosome under the matching number on the magnetic board.
5. Continue this procedure until you have matched all chromosomes and placed each of them in the
corresponding magnetic board.
6. In the event that you have an extra chromosome, DO NOT THROW IT OUT OR DISCARD IT! It is the
chromosome that causes your mutation/disorder and you must match it correctly.
7. Repeat steps 1-6 for your second set of chromosomes. KEEP THE 2 SETS SEPARATED!!!
8. Once your chromosomes are all placed correctly on the magnetic boardS answer the questions and
complete the lab.
Data:
Karyotype 1: Set _________
Karyotype 2: Set _________
Total # of chromosomes:____________
Total # of chromosomes:____________
Normal or Abnormal (circle one)
Normal or Abnormal (circle one)
How do you know?
How do you know?
Name of Chromosomal Disorder: (if any, see key)
Name of Chromosomal Disorder: (if any, see key)
Sex chromosomes: ______ & ______
Sex chromosomes: ______ & ______
Male or Female (circle one)
Male or Female (circle one)
Conclusion Questions:
1. How many human babies are born with chromosomal abnormalities?
2. How can these abnormalities be detected?
3. What are 3 things that karyotype can reveal?
ONE:
TWO:
THREE:
4. What is an amniocentesis?
5. Where are two sources of fluid that can be used for an amniocentesis?
ONE:
TWO:
6. What two things have to be done to chromosomes BEFORE a karyotype can be created?
ONE:
TWO:
7. How are chromosomes arranged in a karyotype?
8. How many chromosomes does a person with a normal karyotype have?
9. A karyotype reveals that a baby has the sex chromosomes XX. What gender is the child?
10. A karyotype reveals that a baby has the sex chromosomes XY. What gender is the child?
11. An abnormal karyotype may have only 45 or 47+ chromosomes, how does this occur?
12. What is it called when chromosomes or chromatids fail to separate?
Refer to the completed abnormal karyotype that you assembled for questions #13-15.
13. What chromosomal abnormality will/does this child have? (i.e. Trisomy 8: 1 extra chromosome
#8, Mosaic Syndrome)
14. How common is this disorder for babies born?
15. What are some of the symptoms of the disorder?
16. If a human gamete with one extra chromosome participates in fertilization with a normal human
gamete, how many chromosomes will the zygote (fertilized egg) have?
17. If a human gamete with one missing chromosome participates in fertilization with a normal
human gamete, how many chromosomes will the zygote (fertilized egg) have?
18. If non-disjunction occurs in humans for one pair of homologous chromosomes during Meiosis I,
will any normal gametes result? What chromosome number would each of the four gametes have?
Gamete 1:
Gamete 2:
Gamete 3:
Gamete 4:
19. If non-disjunction occurs in humans for sister chromatids of one chromosome during Meiosis II,
will any normal gametes result? What chromosome number would each of the four gametes have?
Gamete 1:
Gamete 2:
Gamete 3:
Gamete 4:
20. Many genetic disorders are caused by errors (mutations) in the genes on our chromosomes.
Usually, in disorders caused by chromosomal abnormalities, the genes themselves are not
mutated; rather, there are too many or too few of them. Why do you think that having too many or
too few normal genes created disorders?
Chromosomal Abnormalities Key
Extra chromosome 21 Down Syndrome
Occurs in 1 in 700 births in U.S.
Children with Down syndrome have a distinct facial appearance. Though not all children with Down syndrome have the same
features, some of the more common features are:
 Flattened facial features
 Small head
 Short neck
 Protruding tongue
 Upward slanting eyes, unusual for the child's ethnic group
 Unusually shaped ears
Children with Down syndrome may also have:
 Poor muscle tone
 Broad, short hands with a single crease in the palm
 Relatively short fingers
 Excessive flexibility
Infants with Down syndrome may be of average size, but typically they grow slowly and remain shorter than other children of
similar age. In general, developmental milestones, such as sitting and crawling, occur at about twice the age of children
without impairment. Children with Down syndrome also have some degree of mental retardation, most often in the mild to
moderate range
Extra chromosome 13 Edwards Syndrome
Occurs in about 1 out of every 5000 live births
Edwards' syndrome is usually fatal, with most babies dying before birth. Of those who do make it to birth, 20–30 percent die
within one month. However, a small number of babies (less than 10 percent) live at least one year.
Most children born with Edwards' syndrome appear weak and fragile, and they are often underweight. The head is unusually
small and the back of the head is prominent. The ears are malformed and low-set, and the mouth and jaw are small
(micrognathia). The baby may also have a cleft lip or cleft palate . Frequently, the hands are clenched into fists, and the index
finger overlaps the other fingers. The child may have clubfeet, and toes may be webbed or fused.
Numerous problems involving the internal organs may be present. Abnormalities often occur in the lungs and diaphragm (the
muscle that controls breathing), and blood vessel malformations are common. Various types of congenital heart disease ,
including ventricular septal defect (VSD), atrial septic defect (ASD), or PDA (patent ductus arteriosus ), may be present. The
child may have an umbilical or inguinal hernia , malformed kidneys, and abnormalities of the urogenital system, including
undescended testicles in a male child (cryptochordism).
Extra chromosome 18 Patau Syndrome
Occurs in about 1 out of every 10,000 newborns
Patau syndrome is the least common and most severe of the viable autosomal trisomies (chromosomal abnormality with 3
copies of a chromosome). Median survival is fewer than 3 days.
Newborns with Patau syndrome that survive to gestation and birth share common abnormalities, such as extra fingers or toes,
deformed feet – also known as rocker-bottom feet, various neurological problems including small head – microcephaly, failure
of the forebrain to properly split during gestation, chronic deficiency, different facial defects including small eyes, malformed
nose, cleft lip or cleft palate, heart and kidney defects or abnormal genitalia.
XXY Klinefelter Syndrome
Occurs in 1 in 2000 births
Klinefelter syndrome is one of the most common genetic conditions affecting males.
Klinefelter syndrome adversely affects testicular growth, and this can result in smaller than normal testicles. This can lead to
lower production of the sex hormone testosterone. Klinefelter syndrome may also cause reduced muscle mass, reduced body
and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone with it develops signs
and symptoms.
Klinefelter syndrome often isn't diagnosed until adulthood. Most men with Klinefelter syndrome produce little or no sperm.
But assisted reproductive procedures may make it possible for some men with Klinefelter syndrome to father children.
XYY Double Y Syndrome
Occurs in 1 in 1000 births
Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical
features. Most males with 47,XYY syndrome have normal sexual development and are able to father children.
47,XYY syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language
skills. Delayed development of motor skills (such as sitting and walking), weak muscle tone (hypotonia), hand tremors or
other involuntary movements (motor tics), and behavioral and emotional difficulties are also possible. These characteristics
vary widely among affected boys and men.
XO - missing sex chromosome Turner Syndrome
Occurs in 1 in 5,000 births
Turner syndrome, a condition that affects only girls and women, results from a missing or incomplete sex chromosome.
Signs and symptoms of Turner syndrome may vary significantly. In some girls, a number of physical features and poor growth
are apparent early.
Signs and symptoms that may be apparent at birth or during infancy include:
 Wide or web-like neck
 Receding or small lower jaw
 High, narrow roof of the mouth (palate)
 Low-set ears
 Drooping eyelids
 Short fingers and toes
 Slightly smaller than average height at birth
 Delayed growth
For some girls, the presence of Turner syndrome may not be readily apparent. Signs and symptoms in older girls,
adolescents and young women that may indicate Turner syndrome include:
 No growth spurts at expected times in childhood
 Short stature, with an adult height of about 8 inches (20 centimeters) less than might be expected for a female
member of her family
 Learning disabilities, particularly with learning that involves spatial concepts or math, though intelligence is
usually normal
 Difficulty in social situations, such as problems understanding other people's emotions or reactions
 Failure to begin sexual changes expected during puberty — due to ovarian failure that may have occurred by birth
or gradually during childhood, adolescence or young adulthood
 Early end to menstrual cycles not due to pregnancy
 For most women with Turner syndrome, inability to conceive a child without fertility treatment
Teacher Key for Team Sets
Team Set 1
 B = Normal, Female
 M = Downs, Male
Team Set 2
 G = Normal, Male
 K = Turners, Female
Team Set 3
 C = Normal, Female
 O = Kleinfelters, Male
Team Set 4
 H = Normal, Male
 L = Patau, Female
Team Set 5
 D = Normal, Female
 F = Downs, Male
Team Set 6
 I = Normal, Male
 N = Edwards , Female
Team Set 7
 E = Normal, Female
 A = Double Y, Male
Teacher Demo
 J = Normal Female