Name: ______Per _____ Date_____

Human Karyotype Lab

Pre-Lab Questions – Read the background material presented in the lab packet, and answer the following questions:

  1. What is a karyotype?
  1. What is a centromere? Draw a picture that labels this structure:
  1. How are chromosomes arranged in a karyotype?
  1. What are the first 22 pairs of chromosomes called? ______The 23rd pair? ______
  1. Describe the appearance of the X and Y chromosomes.

6. Using table 1, identify the syndrome with each of the following karyotypes:

Karyotype / Syndrome / Description
XXY
Extra #21
Extra #18

7. An error in what process results in an abnormal number of chromosomes (more or less than 46)?

  1. What is nondisjunction? What does it result in? When can it occur?

Analysis Questions

  1. How many chromosomes are on your sheet? ______

2. What are the possible karyotypes that you could have? (look at table 1 or 2)

  1. Is your karyotype of a male or a female? ______How do you know?
  1. What disorder (if any) will the baby have? ______
  1. How do you know?
  1. If your job were to inform the parents of the fetus of their test results, what would you say?

Table 1: Characteristics Associated with Defective Karyotypes

Syndrome / Karyotype / Characteristics
Klinefelter’s Male / XXY / Unusual body proportions and sterility, subnormal mental ability
Jacob’s SyndromeMale (Supermale) / XYY / Tall, prone to acne, impaired fertility, mentally normal
Turner’s Female / XO / Short stature, webbed neck, may have low mental ability and sterility
Super Female / XXX / May have low to normal mental ability, fertile
Patau’s Syndrome / Extra # 13 / Physical abnormalities, lethal soon after birth
Edward’s Syndrome / Extra # 18 / Unusual features of the head and fingers; often dies in infancy
Down’s Syndrome / Extra # 21 / Characteristics facial features, low mental ability, stocky build, sometime heart defects

Table 2: Human Karyotypes

Syndrome / Karyotype / # of Chromosomes
Normal Male / XY / 46
Normal Female / XX / 46
Klinefelter’s male / XXY / 47
Jacob’s Syndrome Male (Supermale) / XYY / 47
Turner’s Female / XO / 45
Super Female / XXX / 47
Patau’s Syndrome / 3 copies of # 13 / 47
Edward’s Syndrome / 3 copies of # 18 / 47
Down’s Male / 3 copies of # 21 / 47

Table 3 – Use as a guide to see what each chromosome looks like.

Human Karyotype Lab
A karyotype is the display of a person’s chromosomes. A picture of the chromosomes is taken while a cell is undergoing mitosis (specifically, metaphase). The picture is then enlarged cut up so that each chromosome is removed. The chromosomes are matched up and attached to a paper according to size. The chromosomes pairs are numbered from largest to smallest. The first 22 pairs of chromosomes match up exactly – these are autosomes. Then the sex chromosomes (the 23rd pair) are paired, in the female (XX) the chromosomes match and in the male (XY) the chromosomes do not match. Karyotype analysis is often used to determine whether a particular disease or syndrome is present in a fetus. See table 1 and 2 for possible syndromes or diseases.

Chromosomal abnormalities often result from nondisjunction, the failure of the chromosomes to separate properly during meiosis (specifically anaphase I or anaphase II). Nondisjunction results in cells that have too many or two few chromosomes. Trisomy is an abnormality in which a cell has an extra chromosome, or section of a chromosome. The means a cell contains 47 instead of 46 chromosomes. Down syndrome, or trisomy 21, is a chromosomal abnormality that results from having an extra number 21 chromosome.

In this lab, you will complete and analyze a karyotype of cells from a fetus to determine the sex of the fetus and whether or not the fetus has a chromosomal disorder.

Procedure

  1. Pick a chromosome spread – RECORD the letter of your karyotyping form
  2. Count the number of chromosomes present on your spread
  3. Carefully cut out each chromosome (leave a slight margin around each chromosome)
  4. Arrange the chromosomes into homologous pairs- about the same size and shape – note that each chromosome consists of two sister chromatids connected by a centromere. The position of the centromere divides the chromosome into two long arms and two short arms.
  5. Arrange the pairs within the groups in order of decreasing size (I will indicate the X chromosome for you, the Y chromosome is the smallest chromosome)
  6. Glue or tape the chromosomes to the karyotyping form –place the pairs in order, with the longest pair at position 1, the shortest pair at position 22, and the sex chromosomes at position 23.
  7. Analyze your karyotype to determine the sex of the individual and indicate whether or not the individual will have a chromosomal disorder (see table 1 and 2).
  8. Answer analysis questions
  9. Clean up any scraps of paper before you leave class!

10.Turn in completed lab!