Module 3
1. Module 3
1.18. Page 3
Module 3—The Male and Female Reproductive Systems
Reflect and Connect
From the time a pregnancy is confirmed, everybody wonders if the developing baby will be a boy or a girl. Normal embryonic sex determination is a complex process requiring that numerous events take place in the correct order. If all events proceed successfully, a “gender-normal” boy or girl will be born. You know that if two X chromosomes combine at conception, the zygote will develop into a female, and if one chromosome is X and the other is Y, then the zygote will develop into a male. Reflect on how that unicellular zygote develops into a multicellular organism with special sex characteristics. Later in the unit you will examine the factors that contribute to the translation of XX or XY into a sexual individual. Your understanding of the development of Jane and John’s twins into one female and one male child should be falling into place.
Discuss
Choose one, some, or all of the following questions to discuss with your peers and teacher.
D 1. What is the advantage of having more than one gender in a species?
D 2. Historically, women have been held responsible for not producing male children. How has science helped to change this view? Are there places where the historical view is still held?
D 3. Should gender be tested for at birth? Why or why not?
D 4. Are there ways to predict whether a pregnancy will result in a boy or girl before the birth?
D 5. How many sex chromosomes does a platypus have?
After reviewing the responses of other students to the questions, has your view or understanding changed? Is so, how? Record a reflection in your course folder.
Reflect on the Big Picture
For Jane and John, having different gendered twins was a great way to start their family. However, during the twins’ development into one male and one female embryo, an abnormality developed in the female fetus. She was born with only one X chromosome, a condition called Turner syndrome. The explanation for and results of this missing chromosome will be discussed in Unit C.
Keep track of what is happening with Jane and John by recording the information you learned about their experience in your course folder.
Going Beyond
You may have noticed that there are often exceptions to the rule in biological studies. This is the case with respect to the X and Y chromosomes that determine gender. It is possible during gamete formation that the TDF gene can be transferred incorrectly or can be missing altogether. Conduct research to find out how individuals can be male with a genotype of XX and female with a genotype of XY.
Module 3: Lesson 4 Assignment
There is no assignment for this lesson.