Deck 22: An Introduction to Animal Development

Question 1

Cytoplasmic contents in the fertilized egg move along microtubule networks.What kinds of proteins would you predict would facilitate these movements?

A)enzymes
B)kinesins
C)tubulins
D)keratins
E)collagens

Answer 1

B

Question 2

Which of the following directors of embryonic development can be found in the unfertilized egg?

A)tissue-specific proteins
B)proteins in the organizer region
C)cytoplasmic determinants
D)mRNAs from embryonic genome
E)proteins in the gray crescent

Answer 2

C

Question 3

If microtubule formation were disrupted experimentally by the use of drugs,the effects might include all of the following EXCEPT

A)failure of cytoplasmic RNAs to be translated into zygote proteins.
B)failure of organizer formation in the fertilized egg.
C)failure of gastrulation of the embryo.
D)failure of transcription of tissue-specific mRNAs.

Answer 3

A

Question 4

In many animal embryos,the eye is the first organ to develop.The Pax6 protein is important to eye development;its absence may prevent the formation of eyes in mice and humans.Pax6 probably acts as a(n)

A)structural protein in cells of the retina.
B)intercellular signal between retinal and lens cells.
C)transcriptional factor for photoreceptors.
D)extracellular matrix protein secreted by the retina.

Question 5

During gastrulation in amphibians,the presumptive mesoderm moves into the interior of the embryo by following fibrils of fibronectin.The fibronectin is probably secreted by which cells?

A)endodermal cells on the exterior of the embryo
B)mesodermal cells that develop on the inside of the blastocyst
C)ectodermal cells that line the inside of the blastocoel
D)endodermal cells that migrate to the inside of the blastoceol

Question 6

The function of the acrosomal complex during fertilization is

A)to block polyspermy.
B)to dissolve the coating of the egg.
C)to nourish the sperm mitochondria.
D)to permit maximum sperm motility.

Question 7

Which of the following is the most basic process in the developing embryo because all of the other processes listed can occur only after or in conjunction with it?

A)organogenesis
B)cell differentiation
C)mitosis
D)morphogenesis
E)germ layer formation

Question 8

What is a major difference between the development of Drosophila or Xenopus and that of humans?

A)Drosophila and Xenopus do not undergo gastrulation;humans do.
B)Drosophila and Xenopus undergo metamorphosis;humans do not.
C)Drosophila and Xenopus do not show development of germ layers;humans do.
D)In Drosophila and Xenopus,the notochord remains;in humans,it disappears.
E)Drosophila and Xenopus do not undergo blastula formation;humans do.

Question 9

Scientists using RNA hybridization techniques found that a transcription factor called macho-1 localized to some cells during early cleavage,but not others.Descendents of these cells produce mesodermal derivatives.Which structures might not be found in embryos depleted of macho-1?

A)neural tube
B)somites
C)digestive system
D)skin

Question 10

In mammals,the zona pellucida is digested during the process of fertilization.This structure is probably similar to

A)the cortical granules of the sea urchin egg.
B)the jelly layer of the sea urchin egg.
C)the vitelline envelope of the sea urchin egg.

Question 11

Chordin is an organizer protein found only in the dorsal regions of Xenopus laevis embryos.An antibody to chordin might disrupt the determination of which structure?

A)central nervous system
B)digestive system
C)kidneys
D)lungs

Question 12

Many amphibian species release their sperm and eggs directly into a watery environment.All of the following mechanisms might ensure species-specific fertilization in these populations EXCEPT

A)acrosomal complexes in sperm.
B)complex coverings of the egg.
C)specific protein binding between sperm and egg.
D)fertilization envelopes.
E)blocking of non-species-specific mRNA sequences.

Question 13

Suppose an antibody to bindin was introduced into a chamber containing sea urchin sperm and eggs.What might be the result of this experiment?

A)Sperm would fertilize the eggs normally.
B)Sperm would not clump together.
C)Sperm would not be attracted to the egg surface.
D)Sperm would not be motile.

Question 14

One difference between early development in humans and in Xenopus is that

A)in humans,there is no formation of the blastula;in Xenopus,the blastula is a critical stage in early embryogenesis.
B)in humans,blastocysts implant into the uterine wall;there is no implantation in Xenopus.
C)in humans,gastrulation is delayed as the egg moves along the fallopian tube;in Xenopus,gastrulation takes place immediately after blastula formation.
D)in humans,the yolk sac is much smaller than that seen in Xenopus.
E)in humans,neurulation occurs immediately after cleavage;in Xenopus,neurulation is delayed until after gastrulation.

Question 15

In Xenopus embryos,which developmental sequence is correct?

A)neurula,blastula,gastrula,cleavage
B)cleavage,neurula,gastrula,blastula
C)gastrula,neurula,cleavage,blastula
D)cleavage,blastula,gastrula,neurula
E)cleavage,gastrula,blastula,neurula

Question 16

Where do you suppose the first microtubules will be observed in the fertilized egg?

A)immediately beneath the plasma membrane
B)at the site of sperm entry
C)opposite the site of sperm entry
D)around the nucleus

Question 17

During early cleavage in animal embryos,minimal growth of the embryo is observed,even though rapid cell division is taking place.How might this lack of growth be most easily measured without destroying the embryo?

A)oxygen uptake measurements
B)vital dye uptake measurements
C)measurements of embryo movement
D)counting the number of nuclei in the embryo

Question 18

During organogenesis,the first organ system to begin forming in animal embryos is

A)the digestive system.
B)the nervous system.
C)the endocrine system.
D)the circulatory system.
E)the excretory system.

Question 19

What happens during gastrulation?

A)The neural tube-precursor of the spinal cord and brain-forms.
B)Basal and apical cells-precursors of the suspensor and embryo,respectively-form.
C)The fertilized egg divides without growth occurring,forming a ball of cells.
D)Massive movements of cells make the primary body axes visible and organize the three embryonic tissues.

Question 20

What happens during cleavage?

A)The neural tube-precursor of the spinal cord and brain-forms.
B)Basal and apical cells-precursors of the suspensor and embryo,respectively-form.
C)The fertilized egg divides without growth occurring,forming a ball of cells.
D)Massive movements of cells make the primary body axes visible and organize the three embryonic tissues.

Question 21

Given the relative positions of the three embryonic germ layers in the gastrula,which of these layers contributes to the formation of the gut?

A)mesoderm
B)ectoderm
C)endoderm
D)All three layers contribute equally to formation of the gut.

Question 22

A sea urchin egg has a membrane "envelope" around it.What does this tell you about the egg?

A)The egg is ready to be fertilized by the sperm cell.
B)The egg has recently been fertilized by a sperm cell.
C)The egg is developing and is not ready to be fertilized.
D)The sperm entered the egg,but further cell division did not occur.

Question 23

The cells of the somites are determined to become all of the following tissues EXCEPT

A)bone tissue.
B)muscle tissue.
C)nervous tissue.
D)skin tissue.
E)connective tissue.

Question 24

During fertilization in sea urchins,the protein bindin binds to a bindin receptor on the egg.How would the process of fertilization be affected if a mutation was present in the binding receptor?

A)The sperm would still penetrate the egg but further cell division would not occur.
B)The sperm would not bind to the surface of the egg and so fertilization will not occur.
C)The mutated receptor would allow multiple sperm cells to enter the egg (polyspermy).

Question 25

Sperm-egg interactions are species-specific in sea urchins,but not in mammals.What might be one reason for this difference?

A)Other kinds of signals serve similar functions in mammals.
B)Sperm-egg recognition relies on egg cytoplasmic components in mammals.
C)Sperm have evolved to become more selective in mammals.
D)Sea urchin fertilization occurs in open ocean.

Question 26

What do fertilization envelopes and mammalian enzymes modifying proteins on the egg-cell surface have in common?

A)They are mechanisms that aid in fertilization.
B)They are mechanisms that prevent polyspermy.
C)They are mechanisms that prevent organogenesis.
D)They are mechanisms that promote neurulation.

Question 27

Spina Bifida is one of the most prevalent of human birth defects.The defect usually involves the spinal cord or the spinal canal opening to the outside of the body.In severe cases,movement of the legs may be limited or entirely absent.At which stage of development is this defect likely to occur?

A)formation of the neural tube
B)formation of the gastrula
C)formation of the notochord
D)formation of the somites
E)formation of the lateral mesoderm

Question 28

Bicoid is a cytoplasmic determinant that is highly concentrated in the anterior end of a fly egg.Which of the following is most likely to result if there was a mutation that resulted in Bicoid being expressed equally throughout the egg?

A)All the blastomeres would be similar to each other.
B)The blastomeres in the anterior end would produce posterior structures.
C)All of the blastomeres would produce anterior structures.
D)Blastomeres in the posterior would produce anterior structures.

Question 29

You have engineered a molecule that binds to the bindin-like protein on human sperm and can be administered to males.Which of the following would be a consequence of such a drug?

A)Fertilization would increase significantly as the sperm would bind to the egg-cell receptor with greater affinity.
B)Fertilization would not take place as the sperm would not be able to bind to the egg-cell receptor.
C)The sperm would not be able to mature,but could still bind the egg-cell receptor.
D)The gradient of bindin-like protein would be abnormal,resulting in a lack of organogenesis.

Question 30

The TUNEL assay detects apoptotic cells through a dye or precipitate.What does this dye/precipitate bind to?

A)extracellular receptors
B)mRNAs and tRNAs
C)gastrulating embryos
D)mesodermal tissues
E)damaged DNA

Question 31

Why is the fertilized egg considered totipotent,while the cells of the inner cell mass (ICM)are pluripotent?

A)The egg produces all cells of the embryo and the extra-embryonic tissues,while the ICM form only cells of the embryo.
B)The egg produces only the cells of the embryo,while the ICM will form all the cells of the extra-embryonic tissues.
C)The egg produces only the cells of the extra-embryonic tissues,while the ICM produces both the embryonic and extra-embryonic tissues.

Question 32

During gastrulation,mesoderm is found between the ectoderm and the endoderm.The mesoderm gives rise to all of the following EXCEPT

A)the skin epidermis.
B)the circulatory system.
C)the lining of the body cavity.
D)the skeletal system.

Question 33

What is the external layer of the head of a sperm cell called?

A)vitelline envelope
B)zona pellucida
C)acrosome
D)cortical granules

Question 34

Why would an increased level of calcium ions be observed in a newly fertilized sea urchin egg?

A)Calcium facilitates the binding of bindin to the bindin receptor.
B)Increased calcium allows the sperm and egg nuclei to join efficiently,resulting in the formation of a zygote nucleus.
C)Calcium promotes release of proteases from the egg,which digest the egg-cell receptor and prevent polyspermy.
D)Calcium promotes an influx of water that results in a fertilization envelope.
E)Answers C and D

Question 35

What is the role of calcium signalling in prevention of polyspermy?

A)Calcium is toxic to the sperm and kills the sperm preventing fertilization.
B)Calcium signalling results in formation of a fertilization envelope.
C)Calcium signalling directs the sperm to another egg in the vicinity.
D)Increases in calcium ensure there is no room for the sperm to fertilize the egg.

Question 36

Apoptosis has been found to begin early on in development (i.e.prior to gastrulation).How would a lack of apoptosis affect the process of development?

A)Neural tube closure would not occur.
B)The epidermis layer would join together.
C)Formation of the blastopore would not occur.
D)Formation of the notochord would not occur.

Question 37

When a somite matures,the fact that it will become a specific cell type is referred to as which of the following?

A)cell specification
B)cell determination
C)cell differentiation
D)cell gastrulation

Question 38

Which of the following is the correct sequence in the development of specialized cells?

A)differentiation,pattern formation,morphogenesis,determination
B)differentiation,determination,morphogenesis,pattern formation
C)pattern formation,determination,morphogenesis,differentiation
D)pattern formation,morphogenesis,differentiation,determination
E)pattern formation,morphogenesis,determination,differentiation

Question 39

Figure 22.1
Refer to the figure above to answer this question.You are a researcher studying animal development in salamanders.You remove cells from the area facing away from the neural tube and transplant them to the area of the somite next to the neural tube.What will happen to your transplanted cells?

A)They develop into limb muscle.
B)They develop into back muscle.
C)They do not develop.
D)They develop into both limb and back muscle.

Question 40

What would be one clue that you are observing cell differentiation in a frog embryo?

A)Somites are forming as distinct masses on either side of the neural tube.
B)Cells of the lateral mesoderm are undergoing rapid cell division.
C)Cells of the primitive retina are beginning to synthesize pigment molecules.
D)The embryo has developed a chambered heart.