Friday (11/08) Gene Expression Intro

In humans and many other animals, sex is determined genetically at fertilization. A female's egg cell carries an X chromosome while the male's sperm cell can either carry an X or a Y chromosome.

A female embryo is a result of an X chromosome from a female gamete and an X chromosome from a male gamete.

A male embryo is a result of an X chromosome from a female sex cell and a Y chromosome from a male sex cell.

However turtles rely on a process called Temperature-Dependent Sex Determination (TSD). This means that the temperature during the incubation period of the embryo will determine the sex of the offspring.

How does TSD work?

Genes are sections of DNA that provide the instructions for building proteins. Temperature influences gene expression like a switch, turning ON or OFF specific genes that control the development of female or male characteristics. The specific gene responsible for sex determination is called, Dmrt1.

What is gene expression?

Gene expression is a regulated process that is impacted by internal and external factors. For example temperature is an external factor that can activate (switch ON) or deactivate (switch OFF) genes that are then expressed through protein synthesis.