X or Y: Does It Make a Difference?
Normal human genes: Male XY genes (left); Female genes XX genes (right).
© Wessex Regional Genetics Centre/Wellcome Images. CC-BY-NC-ND 4.0
- Length: 60 Minutes
- Objectives and Standards
- Materials and
- Procedure and
- Handouts and
Detailed studies of the sequence and gene activity within the human X chromosome are providing interesting insights and raising questions about the differences between males and females. Women have two X chromosomes while men have an X and Y. The Y chromosome is relatively gene-poor. In women, one of the X chromosomes is partially shut down in each cell. Adding additional interest to the picture is that more than 300 diseases have already been associated with the X chromosome.
Objectives and Standards
Cells store and use information to guide their functions.
Cell functions are regulated through selective expression of individual genes.
Molecular Basis of Heredity
Instructions for specifying the characteristics of the organism are carried in DNA.
There is a pair of chromosomes that determines sex.
Materials and Setup
Teacher Materials (see Setup)
Computer, projector and projection screen
PowerPoint® slides number 8 "The Human Genome," and number 14, "Regulation of the Human Genome (IV)," from the slide set "Molecular Basis of Heredity: Part 2. Genomes."
Overhead projector (optional, see Setup)
Transparencies of slides (optional)
Materials per Group of Students
Computer access for each group member, with four different articles per group preloaded, OR one set of articles listed below (see Setup)
Materials per Student
Copy of "Category Notes" and "3-2-1" student sheets
Prepare to project the slides (see Teacher Materials, above) from a computer OR make transparencies of the slides and use an overhead projector.
Each student group member will read a different article (below). Have students read the articles online, OR make a photocopied set for each group and distribute before beginning the activity.
If students will read the articles online, pre-load the articles before class.
Procedure and Extensions
Begin a class discussion. Ask students, What do you know about the X and Y chromosomes in humans?
Have students record at least one question they have about the X and Y chromosomes in the space provided on the "Category Notes" page.
Project and discuss the slide, "The Human Genome," followed by the slide, "Regulation of the Human Genome IV."
Prompt students to add notes to the first column of their "Category Notes" page.
Divide students into groups of four. Have each student group member to read a different article, either online or a photocopied version (see Setup).
"Researchers Unravel Secrets of X Chromosome." Apr. 2005, From the Labs
"Y Chromosome Reveals Hidden Sequence." Jan. 9, 2005, Nature News
"Women Get Extra Dose of X Chromosome Genes." Mar. 16, 2005, Nature News
"Studies Expand Understanding of X Chromosome." Mar. 16, 2005, NIH News
Distribute and ask each student to complete the "3, 2, 1" activity sheet. Have students list three things they learned, two things that surprised them, and one new question they have after reading their articles.
As a group or class, decide on and add information to the second column of the notes.
Ask each student to highlight the most important information in the first two columns of the "Category Notes" page. In the third column, have each student explain the significance of the highlighted information he or she chose.
Not all animals have the same genetic strategy for determining sex. Have students read and then discuss the article, "Duck-billed Platypus Boasts Ten Sex Chromosomes." Oct. 25, 2004, Nature News.
Have students investigate other organisms. This is a great time to discuss adaptation and evolutionary successes. For example, ask students, Why is there an evolutionary advantage to having two sexes?
Handouts and Downloads
Overview and benefits of the “5-E” teaching model, and keys for successfully incorporating this model into inquiry science teaching.
What determines the physical and biological characteristics of an individual organism, and how are these traits passed from one generation to the next? In this presentation, Dr. McNeel describes the basics of genetic inheritance.
Mendel used experimental approaches to characterize a particulate model of inheritance. In doing so, he developed the three Laws of Inheritance. Examine how Mendel made his important discoveries.
A pedigree shows how a trait is inherited over several generations. Dr. Lisa Meffert explains why pedigrees are important, and the key factors scientists consider when studying pedigrees.