Karyotype Chromosome Spread #
Names:
LAB: Karyotypes and Chromosomes
from Edwards, Jan 1998 revised Dec 2000
When a woman is pregnant she can have a test done to check the chromosomes of her
fetus. The mother and doctor want to know if the chromosomes of the baby are normal. They
also want to know the gender of the baby. Chromosomes carry all the information that makes
someone a person. A normal person has 46 chromosomes in every cell of the body, except for
sperm and egg. The sperm and egg only have 23 chromosomes.
To obtain chromosomes of the fetus, the doctor will perform a procedure called
amniocentesis. She will insert a long needle into the mother’s uterus to remove some of the
amniotic fluid which surrounds the fetus. The amniotic fluid will contain some cells which have
flaked off the fetus. Next the doctor will send the cells in the amniotic fluid to a lab where a
technician will culture more of the fetus’ cells. Over a period of several days, the technician will
look for cells performing mitosis because during mitosis he will be able to see the individual
chromosomes. When he finds a cell in mitosis, the technician will take a photograph of that cell.
He will cut out the chromosomes and match them into their pairs, called homologues. A picture
of the fetus’ chromosomes arranged into pairs is called a karyotype. The doctor will examine
the karyotype to find the gender of the fetus and also to see if the fetus has normal chromosomes.
The diagram below shows a normal karyotype. The fetus has 46 chromosomes and they are
arranged into 23 pairs, 44 are autosomes and two are sex chromosomes. During this lab you are
going to make a karyotype then check it to see if the fetus has a normal set of chromosomes.
PURPOSE:
What are you supposed to do during this lab?
Autosomes of normal human
Sex chromosomes
Male
Female
DATA:
1. Which set of chromosomes did you receive? (which letter or number is on your scatter
sheet?)
Cut out the chromosomes on your scatter sheet one at a time. Match the homologous
chromosomes together. A good strategy is to find the sex chromosomes first and set them aside
so you don’t mix them up with the other autosomes. Glue the pairs onto a Karyotype paper.
2.
Is the fetus on your scattersheet a male or female? How do you know?
3.
How many chromosomes does the fetus on your scattersheet have? How many pairs?
4.
How may autosomes does the fetus on your scattersheet have?
How many sex chromosomes does the fetus have?
5.
What will the doctor tell the mother about the fetus? (does the fetus have normal
chromosomes? are there any chromosomal problems? which gender is the fetus?)
SUMMARY QUESTIONS:
(Hint: reread the introduction to this lab.)
Attach your Karyotype Paper to this lab paper.
6.
What is a karyotype?
7.
How does the doctor obtain a sample of the chromosomes from a developing fetus? What is
this procedure called?
8.
How does the technician prepare the karyotype?
9. What are the two kinds of information that a doctor can obtain from a karyotype?
Genetic Disorders
Genetic Disorder
Chromosome Affected
Description of Disorder
Down Syndrome
# 21
Turner Syndrome
Single X in female (XO)
Klinefelter Syndrome
Extra X in Male (XXY)
47 chromosomes, male with an
additional X chromosome,
usually normal in appearance,
normal intelligence, tall,
underdeveloped testes, sterile,
may also cause female
characteristics (breast
development, feminine body
shape).
Jacobs Syndrome
Extra Y in Male (XYY)
47 chromosomes, male with an
additional Y chromosome, low
mental ability, normal in
appearance.
Triple X Syndrome
Extra X in Female (XXX)
47 chromosomes, female with
an extra X chromosome,
normal intelligence, normal in
appearance, may be sterile.
BIOLOGY 3201 CURRICULUM GUIDE
47 chromosomes, mild to
severe developmental
disabilities, almond - shaped
eyes, large tongue, prone to
heart defects and respiratory
problems.
45 chromosomes, female
lacking an X chromosome,
normal in childhood, normal
intelligence, fails to develop
secondary sex characteristics
and remains infertile.
141
Normal Human Karyotype
4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
BIOLOGY 3201 CURRICULUM GUIDE
Chromosome Spread # 1
BIOLOGY 3201 CURRICULUM GUIDE
143
Chromosome Spread # 2
144
BIOLOGY 3201 CURRICULUM GUIDE
Chromosome Spread # 3
BIOLOGY 3201 CURRICULUM GUIDE
145
Karyotype # 1
146
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
BIOLOGY 3201 CURRICULUM GUIDE
Karyotype # 2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
BIOLOGY 3201 CURRICULUM GUIDE
147