ANHB3323 Lecture Notes - Lecture 7: Microtubule, Body Plan, Cell Adhesion

When Sheila and Tyrone's daughter Mallory was born, on June 12. Anika was pregnant.
after she missed her period. Anika and her husband. Jeremy, were thrilled at the news,
Anika's last menstrual period began on April 3, and she's taken a pregnancy test a week
because a few months earlier she'd also thought she was pregnant. At that time, she had
started cramping and bleeding, and an ultrasound scan showed an empty sac- there was
no embryo. Anika knew from her biology classes that this probably meant that a sperm
had entered a polar body, which is a product of meiosis in the female that has very little
cytoplasm and is not the functional equivalent of an oocyte. The hormonal changes
typical of pregnancy had ensued anyway, which was why her pregnancy test had been
positive.
For the current pregnancy, at her first prenatal visit to an obstetrician, an
ultrasound scan confirms that Anika is in her fifth week. This time, instead of an empty
sac, the embryo looks like a lima bean with a pulsating blip in the center- beating
heart.
As Anika gazes at the ultrasound screen in wonder. a nurse looks over her chart
and asks about an acne drug, Accutane, that Anika had taken for several years. The drug.
a derivative of vitamin A. interferes with prenatal development at the fourth week.
disrupting formation of facial features, causing structural defects of the heart, and leading
to low IO and learning disabilities. Fortunately, Anika knew all about these effects and
had long since stopped taking the drug. However, the nurse frowns when she sees a
notation for another drug that Anika is currently taking for a skin condition- the
antibiotic doxycycline. This drug can cause tooth discoloration in childhood following
exposure as a fetus.

1. A polar body cannot sustain development becase

a) it lacks sufficient cytoplasm and organelles

b) it lacks a nucleus

c)its nucleus is diplod

d)it secretes a substance that prevents sperm from swimming

e)it cannot divide

2. The barries that the sperm had to pass to enter the oocyte are

a)the blastocyst and gastrula

b) Anika's parents

c)a layer of follice cells surrounding a layer of glycoprotein

d)the chorionic villi and placenta

e) the seminiferous tubules and the epididymis

3. At the time of Mallory's birth, Anika and Jeremy's child-to-be is

a) a blastocyst

b) a morula

c) a gastrula that has just folded into three layers

d) a primordial embryo

e) on the boundary of the embryonic and fetal periods

4. The approximate date of the conception of Anika and Jeremy's child-to-be is

a)mid october

b) late january

c) mid april

d) late may

e) early september

5. When Anika learns that she is pregnant for the second time, which of the following has already happened?

a) fertilization only

b) ovulation only

c) inner cell mass formation, but not blastocyst formation

d) gastrulation, but not blastocyst formation

e) formation of three primordial germ layers

6. When Mallory is born, her future second cousin already has

a) a placenta

b) eyebrows

c) nipples

d) nails

e) a neural tube

7. The time whena drug affects a prenatal human is called its ___ period

a) menstrual

b) genetic

c) obstetric

d) critical

e) chronological

8. A drug such as Accutane likely causes likely causes more severe birth defects than a drug such as doxycycline because

a)it acts earlier in development

b) it acts later in development

c) it causes dominant mutations

d) it causes recessive mutations

e) it kills sperm