Constructing
Chromosomes
In this activity you will be constructing a model of homologous chromosomes from construction paper.
One chromosome will be constructed from pink paper; one from blue paper. These models will be used in
class activities to recreate the stages of mitosis, the stages of meiosis, and model a human karyotype.
You need to be familiar with the following terms:
sister chromatids - two identical copies of a parent chromosome which are attached to one another at the centromere.
homologous chromosome - chromosomes having the same size, shape, binding pattern, and array of genes; DNA
coding for hair color in the allele from your mother is homologous to DNA coding for hair color in the corresponding allele
from your father.
gene - section of a chromosome which codes for a protein or RNA product.
chromatid - one half of a replicated chromosome which is joined to the other half at the centromere.
chromosomes - discrete structures which occur in eukaryotic cell nuclei, contain one or two DNA double helices (in their
unreplicated and replicated forms respectively), and are associated with protein especially when condensed.
allele - one variant of a particular gene; for example, there are blue and brown alleles of the eye-color gene.
+++Homologous++++ Uniform ++++Neat++++Unique++++ Creative +++Identical++++Consistent+++
STEP 1 – Maternal Homologue
Fold a pink piece of construction paper in half. Draw a single sister chromatid so that its center
point corresponds to the folded edge. Leave the paper folded and cut out the chromatid. (Do not
separate the two sister chromatids.)
Be creative and let your chromatid reflect your personality. Your chromatid should be different
than everyone else in the class.
STEP 2 – Paternal Homologue
Fold the blue piece of construction paper in half. Use the pink chromatid as a template and trace
the single sister chromatid so that its center point corresponds to the folded edge. Leave the paper
folded and cut out the chromatid. (Do not separate the two sister chromatids.)
STEP 3 - Centromeres
Fold a black piece of construction paper in half. Fold it in half again. Draw a circle on the paper (2”
diameter). Cut out the centromere (4).
STEP 4 – Putting it together
Cut each of the sister chromatids (pink and blue) apart at the fold. Glue 1 black centromere to the
front center point of each sister chromatids (4). After the glue has dried, use a paperclip to join the
sister chromatids together.
STEP 5 – Genes – sequence of DNA with instructions for building a specific protein.
Decorate your chromosomes (with stickers, markers, glitter, etc) to designate the specific location
of specific genes on your chromosome. Indicate/label the allele present for each trait. Each
chromosome must include at least 4 genes. Be creative, and make your chromosomes unique.
**Remember- Sister chromatids should be exact copies of one another (size, shape, and allele).
Homologous chromosome will be similar in size, shape, and location of genes (but may vary in the
actual allele).
You now have your very own pair of homologous chromosomes. Make sure you bring them to
class. We will use them over the next couple of classes to demonstrate the processes of mitosis,
meiosis, and karyotyping.