Genetics II: Genes, Chromosomes, and Alleles
I.
Benchmark/ Standard: B4.1 Genetics and Inherited Traits
a. Hereditary information is contained in genes, located in the chromosomes of
each cell. Cells contain many thousands of different genes. One or many
genes can determine an inherited trait of an individual, and a single gene can
influence more than one trait. Before a cell divides, this genetic information
must be copied and apportioned evenly into the daughter cells.
i. B4.1A Draw and label a homologous chromosome pair with
heterozygous alleles highlighting a particular gene location.
ii. B4.1B Explain that the information passed from parents to offspring
is transmitted by means of genes that are coded in DNA molecules.
These genes contain the information for the production of proteins.
iii. B4.1c Differentiate between dominant, recessive, codominant,
polygenic, and sex-linked traits.
iv. B4.1d Explain the genetic basis for Mendel’s laws of segregation and
independent assortment.
v. B4.1e Determine the genotype and phenotype of monohybrid
crosses using a Punnett Square.
I.
Behavioral/ Objective: Students will draw and label a homologous chromosome
pair with heterozygous alleles highlighting a particular gene location and
differentiate between dominant, recessive, codominant, polygenic, and sexlinked traits by creating punnett squares of each and then defining the genotype
and phenotypes of the possible outcomes.
II.
Anticipatory Set: Each student should collect a mini white board, dry erase
marker, and eraser. Project the following prompts under the doc cam one at a
time. Ask students to complete the punnett square crosses and determine the
genotype and phenotype.
a. In dogs, wire hair (S) is dominant to smooth (s). Cross a homozygous wirehaired dog with a smooth-haired dog.
b. In fruit flies, long wings (L) are dominant to short wings (l). Cross a short
winged fly with a heterozygous fly.
c. The ability to curl your tongue up on the sides (T, tongue rolling) is
dominant to not being able to roll your tongue. A woman who can roll her
tongue marries a man who cannot. Their first child has his father's
phenotype. What are the genotypes of the mother, father, and child?
III.
Objective/ Purpose: “Yesterday we were introduced to a lot of new terms. Today
we are going to talk about genes, chromosomes and alleles and what they look
like. I think we have a pretty good grip on dominant and recessive traits, so
today we are going to focus on co-dominant, polygenic, and sex-linked traits.”
IV.
Input:
a. Task Analysis:
i. Give each student a Ziploc bag with the following inside
1. One pipe cleaner cut in half.
2. Four pony beads, two red and two blue
ii. Demonstrate the following under the document camera for students.
1. Blue beads are dominant, red beads are recessive
(R=red/recessive)
2. The two pipe cleaners represent a homologous pair of
chromosomes. On each chromosome there are many genes.
3. The bead represents an allele.
4. Use different combinations of beads to explain genotypes
and phenotypes.
a. Two reds=recessive trait
b. Two blues= dominant trait
c. One red and one blue= dominant trait
iii. Show the class a Karyotype on the projector. Humans have 23 pairs
of homologous chromosomes
1. http://ghr.nlm.nih.gov/handbook/illustrations/normalkaryo
type
2. http://www.biotechnologyonline.gov.au/images/contentpag
es/karyotype.jpg
iv. Human genome project: explain to students and show website on the
projector.
1. http://www.ornl.gov/sci/techresources/Human_Genome/h
ome.shtml
v. Students should use their models to draw model in their notes.
Circulate and check work.
vi. “On our pipe cleaners we have dominant and recessive alleles, but
what about co-dominance, polygenic and sex-linked traits?”
Dominant
Recessive
Co-dominant Polygenic
Sex-linked
Definition
Example
vii. Students should work in pairs to fill in the chart. Put the chart on the
Smart Board. Choose ten students, each one should go up to the
board and fill in a space.
viii. Number students 1-5. Depending on the number, they should
complete a punnett square cross and state the genotype and
phenotype as an example of:
1. Dominant
2. Recessive
3. Co-dominant
4. Polygenic
5. Sex-linked
ix. Share an example of each on the document camera.
x. Learning Log on the back of the chart, students should divide the
paper into six boxes: label the boxes:
1. What I knew already, New vocabulary, Important to
remember, Draw it, This reminds me of, Not so sure about
this
xi. For the next class students should find and read a science article
related to genetics. They should prepare a brief summary of the
article. How did the article relate to what we have learned in class?
What is something new or interesting you learned from the article?
1. Recommended resources:
V.
VI.
VII.
a. http://www.sciencedaily.com
b. http://sciencefriday.com
c. http://www.biologynews.net
Thinking Levels:
i. Knowledge: recognize and define genetic vocabulary.
ii. Comprehension: restate definition in their own words and discuss
the new vocabulary as a class.
iii. Application: use pipe cleaners and beads to represent chromosome
structure.
Learning Styles:
i. Visual: board work, chart, learning log, and pipe cleaner model.
ii. Auditory: lecture and discussion of structure and new vocabulary
iii. Kinesthetic: pipe cleaner model, board work.
Methods and Materials:
i. Ways of presenting: Lecture, document camera, board work.
ii. Materials needed: document camera, computer, projector, white
board. Ziplocs, pipe cleaners, pony beads.
VIII.
Modeling:
a. Model homologous pairs and alleles on chromosomes using pipe cleaners
and beads.
IX.
Check for understanding:
a. Draw homologous chromosome with heterozygous alleles
b. Chart
c. Learning Log
Guided Practice: Teacher will circulate answer questions and assist students
filling in the charts and learning logs.
X.
XI.
Independent Practice:
a. Complete the learning log.
b. Science article and summary
XII.
Closure: Learning Log