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3.1: Planning

Difficulty Level: At Grade Created by: CK-12
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Key Ideas

  • Chromosomes in the nucleus carry the genes responsible for human traits and variations.
  • Chromosomes occur in pairs, with exception of the sex chromosomes that may not be the same.
  • Individuals of the same species have the same number of chromosomes.
  • A karyotype is a “portrait of the chromosomes in a cell.” A karyotype is useful in helping diagnose, learn about, and explain many genetic diseases.


Students describe how geneticists solve problems that help them explain and predict the inheritance of human traits and variations. They review cell structures and identify the nucleus as the location for chromosomes that carry genes as the units of heredity. Students use their knowledge of chromosomes to explain similarities within a species and differences among species. Students apply their knowledge of chromosomes to construct, analyze, and interpret human karyotypes.



  • identify the location of chromosomes.
  • explain that genes are responsible for human traits and variations.
  • explain why chromosomes usually occur in pairs.
  • determine the reason for continuity and diversity within a species.
  • construct, analyze, and interpret a human karyotype.


cells, chromosomes, karyotype, nucleus

Student Materials

Activity 2-1: Karyotyping - A Chromosome Portrait

  • Resources 1 or 2, and 3
  • Activity Report
  • Scissors; Metric ruler; Glue or tape

Teacher Materials

Activity 2-1: Karyotyping - A Chromosome Portrait

  • Activity Report Answer Key
  • Extra student materials
  • Resource 4 and Map of the Human Genome (Optional)

Human Genome Project addresses:

DOE sites




NIH site: National Human Genome Research Institute


Advance Preparation

See Activity 2-1 in the student edition

Activity 2-1: Karyotyping - A Chromosome Portrait

  • Copy Resources 1-3 and the Activity Report.
  • Optional: Review Resource 4, Down syndrome karyotype, to decide whether or not to assign this optional activity. You can copy Resource 4 for students and/or make a transparency of this karyotype.
  • Optional: Arrange for guest speaker (see Helpful Hints).

Interdisciplinary Connections

Health Education Discuss the ethical dilemmas presented when karyotypes are used to get chromosomal information on genetic disorders.

Art Make posters of the karyotypes or collages of chromosomes for display.

Background Information

Karyotyping can be used to diagnose more than 100 genetic diseases during fetal development by a procedure known as amniocentesis. This procedure is usually performed between 16 and 18 weeks of pregnancy. A thin hypodermic needle inserted through the mother's abdomen removes amniotic fluid from the amniotic sac surrounding the developing fetus. The fluid contains fetal cells and other materials shed from the amniotic sac.

The fluid is centrifuged to compact the cells, which are then placed in a growth medium for nourishment. After several days of incubation the dividing cells are removed from the incubator and prepared for a study of the chromosomes. A photograph of the chromosomes is taken and then the magnified chromosomes are paired. The resulting karyotype can be used to identify extra, defective, or missing chromosomes.

The cut and paste procedure that students use in Activity 2-1 has been used to make karyotypes for many years. Today, high-powered microscopes are connected to computers that digitize and print out a karyotype.

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Date Created:
Feb 23, 2012
Last Modified:
Apr 29, 2014
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