What Determines Gender in Humans?
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This page first made public: Jan 15, 2007
This material is replicated on a number of sites as part of the SERC Pedagogic Service Project
In this activity students examine karyotypes from five individuals to try to identify which chromosomes determine gender in humans. By close inspection, they should notice that the number of X chromosomes does not determine gender, but that the presence or absence of a Y chromosome does. In addition, having one extra or one missing chromosome can lead to birth defects and mental retardation. Finally, the mechanism by which extra or missing chromosomes can occur is explored, namely non-disjunction. This can be used in a large lecture setting, or as an out of class homework assignment.
Context for Use
In lecture students are provided with a handout that has pictures of five karyotypes and a table in which to enter data for each karyotype. Similar slides are placed in a powerpoint lecture. Students are asked to fill out the table, and look for a correlation between numbers of X or Y chromosomes and gender. In lecture this exercise takes less than 10 minutes.
As an out of class assignment, students are given the same information and table. In addition, they are provided with a series of questions that walk them through the logic of identifying which chromosomes determine gender.
Description and Teaching Materials
In class, students are given a two page handout with some karyotypes and a table to fill in. The instructor then displays the same karyotypes in class, along with pictures of individuals with that karyotype (optional). The students then fill in the numbers of X, Y and autosomal chromosomes for each individual. The instructor can then ask what appears to determine gender in humans. They can also discuss what happens to individuals with missing or extra chromosomes, and how that can occur.
Out of class, students are given the same data to analyze, and the questions that the instructor would ask in class are presented in the text. There are additional links to help students understand non-disjunction. Gender out of class assignment (Microsoft Word 1MB Jul6 06) Gender lecture handout (Microsoft Word 89kB Jul6 06) Slides for lecture (PowerPoint 1MB Jul6 06) Gender Quiz (Microsoft Word 24kB Jul6 06)
Teaching Notes and Tips
Multiple choice summative assessment questions are provided that can be used as a practice quiz or for points.
References and Resources
MERLOT description of the NOVA site on meiosis resource that is used in this activity.
The following websites can be used by students to understand non-disjunction.