Reproductive System

Reproductive System

Middle School

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Learning Objectives

• Learn how the SRY gene on the Y chromosome helps in developing the testes.

• Understand testosterone's role in male development before birth and during the teenage years.

• Describe the function of estrogen and progesterone in the development of female bodies.

• Identify secondary sexual characteristics that develop in males and females during puberty.

Key Vocabulary

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SRY Gene

A gene on the Y chromosome that triggers the development of testes in an embryo.

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Testosterone

This hormone drives the development of male genitalia and other secondary sexual characteristics during puberty.

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Estrogen

A key hormone for developing female reproductive organs and secondary sexual characteristics during puberty.

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Progesterone

This hormone aids in the development of female reproductive organs and secondary sexual characteristics.

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Gonads

The primary reproductive organs that produce gametes: testes in males and ovaries in females.

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Genetic Determination of Sex

• All embryos have undifferentiated gonads, which can develop into testes or ovaries.

• The SRY gene on the Y chromosome determines the developmental path.

• If the SRY gene is present (XY), the gonads develop into testes.

• If the SRY gene is absent (XX), the gonads become ovaries.

Multiple Choice

What is the primary function of the SRY gene?

• It causes the embryonic gonads to develop into testes.

• It directly produces testosterone.

• It causes the embryonic gonads to develop into ovaries.

• It is responsible for all secondary sexual characteristics.

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Male Reproductive Development

• Testosterone is the key male sex hormone for reproductive development.

• In embryos, it causes the growth of male genitalia.

• During puberty, increased testosterone levels lead to sperm production.

• It also causes a deeper voice, and body and facial hair.

Multiple Choice

Which of the following is a result of testosterone secretion during puberty?

• Development of male secondary sexual characteristics.

• Development of the SRY gene.

• The initial formation of the testes in an embryo.

• The development of ovaries.

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Female Reproductive Development

• Embryos without the SRY gene (XX) develop their gonads into ovaries.

• These ovaries produce female sex hormones called estrogen and progesterone.

• These hormones direct the prenatal development of the uterus and vagina.

• During puberty, they cause secondary sexual characteristics like breast enlargement.

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Multiple Choice

What are the main hormones that cause the development of female secondary sexual characteristics during puberty?

• Estrogen and progesterone

• Testosterone and the SRY gene

• Only testosterone

• Only progesterone

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Common Misconceptions

Misconception	Correction
All embryos start as female.	Embryos have undifferentiated gonads that develop based on genetic signals.
Sex hormones are only produced during puberty.	Sex hormones are also critical for development before birth.
Only males produce testosterone and only females produce estrogen.	Both sexes produce both hormones, but in different amounts.

Multiple Choice

How does the timing of testosterone secretion differ in its developmental effects?

• Secretion before birth develops genitalia; secretion during puberty develops secondary characteristics.

• It only affects development during puberty.

• Secretion before birth develops secondary characteristics; secretion during puberty develops genitalia.

• It only affects development before birth.

Multiple Choice

Why is the SRY gene often called a "master switch" for male development?

• Because its presence triggers a cascade of events, starting with testes development, which leads to all other male characteristics.

• Because it directly builds all male reproductive organs.

• Because it is the only gene on the Y chromosome.

• Because it controls the production of estrogen and progesterone.

Multiple Choice

A person is born with an XY chromosome pair, but their SRY gene is non-functional. What is the most likely developmental outcome?

• The gonads would develop into ovaries, and the person would develop female characteristics.

• The gonads would develop into testes, but no secondary sexual characteristics would appear.

• The person would develop both male and female characteristics equally.

• The gonads would develop into testes, and development would proceed as typical for a male.

Multiple Choice

Which statement best describes the role of the SRY gene and testosterone in the development of a male fetus?

• The SRY gene causes testes to form, which then secrete testosterone, leading to the development of male genitalia.

• Testosterone activates the SRY gene, which causes testes to form.

• The SRY gene directly develops male genitalia without the need for hormones.

• Testosterone is only produced during puberty and has no role in prenatal development.

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Summary

• The SRY gene on the Y chromosome directs embryonic gonads to become testes.

• Without the SRY gene, embryonic gonads develop into ovaries.

• Testosterone from the testes is responsible for the development of male characteristics.

• Estrogen and progesterone from the ovaries guide female development.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4