BIOL 14a Chapter Notes - Chapter 20: Hox Gene, Red Blood Cell, Cellular Differentiation

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28 Jun 2017

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Genetic programs of development, the fertilized egg is a totipotent cell, after fertilization, the zygote undergoes a series of cell divisions and eventually forms a ball of cells, called the morula, and travels to the uterus. It then forms a hollow sphere called the blastocyst and in one region of the inner (cid:462)all there"s a (cid:311)roup o(cid:310) (cid:272)ells (cid:272)alled inner cell mass, where body of embryo develops. Multipotent cells give rise to variety of more specialized cells. Hierarchical control of development: drosophila development proceeds through egg, larval, and adult stages, early nuclear divisions occur w/o cell division so embryo is a single cell with many nuclei in center. When it reaches around 5000, each gets enclosed in a membrane, forming the cell blastoderm. Then, gastrulation begins, where 3 layers of cells form. Already, there is a discrete organization of parts called segmentation. 1 day later, embryo hatches as larva and it grows and replaces outer cell twice.

Related Questions

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

cyanmole529

Please briefly explain reasoning for all questions.

Which of the following is a component of a vertebrate kidney? (Select all correct choices.)

	glomerulus
	Bowman's capsule
	renal tubules
	collecting ducts
	Malphigian tubules

In organisms, the ability to control osmosis depends on the properties of the plasma membranes of individual cells. Based on their ability to permit the free movement of water and some solutes, these membranes are best described as: (select all correct choices)

	impermeable.
	permeable.
	semipermeable.
	diffusible.
	impervious.

True or false: The inner cell mass of the blastocyst becomes the embryo, while the outer cell layer of the blastocyst forms part of the placenta.

	true
	false

Which of the following accurately characterizes the early cleavage divisions in most animals, although not necessarily in mammals?

	They do not involve an increase in the size of the zygote.
	They are directed by the zygoteâs genome.
	They are relatively slow.
	They do not occur at the same time, so at any given moment the zygote may have an odd number of cells.
	All of these choices are correct.

A key difference between hormonal regulation of the reproductive systems of males and females is that:

	LH and FSH are released only in females.
	LH and FSH are released only in males.
	LH and FSH are released cyclically in females but nearly continuously in males.
	LH is released in males and FSH is released in females.
	LH is released continuously in males and FSH is released cyclically in females.

Compared to sexual reproduction, asexual reproduction: (select all correct choices)

	requires less investment in attracting mates.
	allows much more rapid population growth.
	is rarely found as the sole mechanism of reproduction.
	results in the production of genetically identical cells or individuals.
	involves meiosis and fertilization as core processes.

True or false: In response to LH and FSH, ovaries secrete estrogen and progesterone.

	true
	false

During the luteal phase of the menstrual cycle, if the oocyte is not fertilized, a number of events occur which are listed below. Select the answer that places the events in the correct chronological order.

Events:
1. the lining of the uterus is shed
2. the corpus luteum secretes progesterone
3. follicle cells are converted to the corpus luteum
4. the corpus luteum degenerates
5. estrogen and progesterone levels fall

	3, 2, 4, 5, 1
	1, 2, 3, 4, 5
	2, 4, 3, 1, 5
	4, 3, 2, 1, 5
	5, 2, 3, 4, 1

If an antibody is missing its Fc fragment, what would happen if this antibody encounters its target antigen in the bloodstream? Select all correct choices.

	The antibody would be able to bind the antigen at a specific epitope.
	The antibody would be able to bind the antigen, but not at an epitope site.
	The antibody would not be able to bind to the antigen.
	The antibody would be able to activate components of the complement system.
	The antibody would not be able to activate components of the complement system.

10)

If an individual carries a mutation that results in a complete lack of MHC class I proteins, how would the individualâs immune response be affected? Select all correct choices.

	Memory cell antibodies would not be able to attach to antigen epitopes.
	Cytotoxic T cells would not be able to target (and destroy) infected cells.
	Helper T cells would not be able to interact with antigen-presenting cells.
	Plasma cell antibodies would not be able to attach to antigen epitopes.

11)

If an individual carries a mutation that results in a complete lack of MHC class I proteins, how would the individualâs immune response be affected? Select all correct choices.

	Memory cell antibodies would not be able to attach to antigen epitopes.
	Cytotoxic T cells would not be able to target (and destroy) infected cells.
	Helper T cells would not be able to interact with antigen-presenting cells.
	Plasma cell antibodies would not be able to attach to antigen epitopes.

12)

Which of the following statements is true regarding T cell receptors? Select all correct choices.

	They recognize antigen-MHC complexes.
	They contain variable and constant regions.
	They are composed of two heavy (H) chains and two light (L) chains.
	They are formed by the rearrangement of V, J, C, and D gene segments.
	They can be found in the bloodstream independent of T cells.

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BIOL 14a Chapter Notes - Chapter 20: Hox Gene, Red Blood Cell, Cellular Differentiation

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