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BIO 140 Human Biology I - Questions and Solutions

Fertilization - Solutions

Review Questions

1. Sperm and ova are similar in terms of ________.

  1. size
  2. quantity produced per year
  3. chromosome number
  4. flagellar motility

2. Although the male ejaculate contains hundreds of millions of sperm, ________.

  1. most do not reach the oocyte
  2. most are destroyed by the alkaline environment of the uterus
  3. it takes millions to penetrate the outer layers of the oocyte
  4. most are destroyed by capacitation

3. As sperm first reach the oocyte, they will contact the ________.

  1. acrosome
  2. corona radiata
  3. sperm-binding receptors
  4. zona pellucida

4. Fusion of pronuclei occurs during ________.

  1. spermatogenesis
  2. ovulation
  3. fertilization
  4. capacitation

5. Sperm must first complete ________ to enable the fertilization of an oocyte.

  1. capacitation
  2. the acrosomal reaction
  3. the cortical reaction
  4. the fast block

 

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Critical Thinking Questions

1. Darcy and Raul are having difficulty conceiving a child. Darcy ovulates every 28 days, and Raul’s sperm count is normal. If we could observe Raul’s sperm about an hour after ejaculation, however, we’d see that they appear to be moving only sluggishly. When Raul’s sperm eventually encounter Darcy’s oocyte, they appear to be incapable of generating an adequate acrosomal reaction. Which process has probably gone wrong?

Solution: The process of capacitation appears to be incomplete. Capacitation increases sperm motility and makes the sperm membrane more fragile. This enables it to release its digestive enzymes during the acrosomal reaction. When capacitation is inadequate, sperm cannot reach the oocyte membrane.

2. Sherrise is a sexually active college student. On Saturday night, she has unprotected sex with her boyfriend. On Tuesday morning, she experiences the twinge of mid-cycle pain that she typically feels when she is ovulating. This makes Sherrise extremely anxious that she might soon learn she is pregnant. Is Sherrise’s concern valid? Why or why not?

Solution: Sherrise’s concern is valid. Sperm may be viable for up to 4 days; therefore, it is entirely possible that capacitated sperm are still residing in her uterine tubes and could fertilize the oocyte she has just ovulated.

 

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OpenStax, Fertilization. OpenStax CNX. Jun 4, 2013 http://cnx.org/contents/9a0f493d-ab54-4ebe-bf1d-5dc77cdc27c9@3. © Jun 4, 2013 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License 3.0 license.