Question 1

What happens during cleavage?

Accepted Answer

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 2

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

Accepted Answer

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 3

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

Accepted Answer

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

Question 4

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

Accepted Answer

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 5

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?

Accepted Answer

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

Question 6

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

Accepted Answer

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 7

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

Accepted Answer

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 8

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

Accepted Answer

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

Question 9

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?

Accepted Answer

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 10

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

Accepted Answer

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 11

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?

Accepted Answer

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 12

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

Accepted Answer

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 13

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?

Accepted Answer

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

Question 14

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

Accepted Answer

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

Question 15

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?

Accepted Answer

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 16

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

Accepted Answer

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 17

The function of the acrosomal complex during fertilization is

Accepted Answer

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 18

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?

Accepted Answer

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 19

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?

Accepted Answer

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

Question 20

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

Accepted Answer

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

Exam 22: An Introduction to Animal Development