Deck 43: Animal Development

Question 1

A researcher experimentally blocks the protein that inhibits GSK-3 in a frog zygote.Which would be the most immediate effect?

A) GSK-3 would be degraded throughout the cytoplasm.
B) β-catenin would be degraded throughout the cytoplasm.
C) GSK-3 would become localized in the region of the gray crescent.
D) β-catenin would be present throughout the cytoplasm.
E) β-catenin would be more concentrated in the dorsal cells of the early embryo.

Answer 1

B

Question 2

In frogs, the sperm penetrates the egg in the region of the

A) vegetal pole.
B) animal pole.
C) gray crescent.
D) unpigmented cortical cytoplasm.
E) most concentrated yolk.

Answer 2

B

Question 3

Which event occurs during cleavage?

A) Rapid transcription of genes
B) Differential distribution of nutrients and information molecules
C) Cell growth
D) Rapid translation of mRNA into protein
E) A decrease in the DNA-to-cytoplasm ratio

Answer 3

B

Question 4

Frogs display _______ cleavage, whereas Drosophila display _______ cleavage.

A) complete; superficial
B) complete; radial
C) complete; spiral
D) incomplete; complete
E) superficial; complete

Question 5

The mammalian blastocyst differs from a frog blastula in that the mammalian blastocyst

A) lacks a blastocoel.
B) is produced via cleavage.
C) forms after a solid ball of cells has formed.
D) produces both the embryo and support structures, such as the embryonic side of the placenta.
E) lacks blastomeres.

Question 6

Which feature is a characteristic of both fruit flies and birds?

A) Centrally located yolk in the egg
B) Migration of nuclei to the periphery of the egg
C) Incomplete cleavage
D) Larger blastomeres in the animal hemisphere than in the vegetal hemisphere
E) Cycles of mitosis without cell division

Question 7

Which statement about cleavage in placental mammals is true?

A) The number of cells increases regularly, from 2 to 4 to 8 to 16 to 32, etc.
B) It proceeds more quickly than cleavage in frogs.
C) It is characterized by synchronous cell divisions.
D) It is radial.
E) It is influenced by genes that are expressed during cleavage.

Question 8

Which feature is characteristic of cleavage in placental mammals?

A) Begins after the fertilized egg reaches the uterus
B) Is slowed down by large amounts of yolk in the vegetal hemisphere
C) Produces a spherical blastula that is one cell layer thick, similar to that of the sea urchin
D) Has two different planes of cleavage in the second cleavage
E) Undergoes nuclear division in the absence of cytoplasmic division during the first several division cycles

Question 9

In which organism does the nuclear volume increase while the cytoplasmic volume stays the same during early cleavage?

A) Fruit fly
B) Frog
C) Bird
D) Fish
E) Lizard

Question 10

Suppose you are designing an embryology lab and want to expose your students to as many different patterns of cleavage as possible.Which combination of animals would be the most appropriate to include?

A) Frog, snail, bird, fish, fruit fly
B) Snail, bird, lizard, fruit fly, eutherian mammal
C) Frog, bird, fish, fruit fly, eutherian mammal
D) Frog, fish, lizard, snail, fruit fly
E) Frog, snail, bird, fruit fly, eutherian mammal

Question 11

Which feature is characteristic of development in organisms whose eggs have little to a moderate amount of yolk?

A) Incomplete cleavage
B) Discoidal cleavage
C) Embryos that form as blastodiscs
D) A yolk mass below the embryo
E) Early cleavage furrows that divide the egg completely

Question 12

If you were interested in studying spiral cleavage, from which group would you select your study species?

A) Frogs
B) Mollusks
C) Birds
D) Fishes
E) Insects

Question 13

In a placental mammal, destruction of cells within the inner cell mass is most likely to impair which event?

A) Creation of the blastocoel
B) Formation of structures in the body of the embryo
C) Implantation
D) Formation of the placenta
E) Position of the asters in the second and third cleavage

Question 14

A researcher who wants to block initiation of the cytoplasmic reorganization that is revealed by the appearance of the gray crescent in a developing frog should block the actions of

A) mitochondria contributed by the egg.
B) GSK-3.
C) the centriole contributed by the sperm.
D) β-catenin.
E) GSK-inhibiting protein.

Question 15

Refer to the graph. In the graph, curve _______ best represents the changes in the ratio of nuclear volume to cytoplasmic volume during early cleavage in most animals.At this time, the blastomeres _______ in size.

A) A; decrease
B) B; decrease
C) C; decrease
D) A; increase
E) C; increase

Question 16

Which are least likely to be cytoplasmic determinants that direct embryonic development in frogs?

A) Transcription factors
B) Protein kinases
C) Protein kinase inhibitors
D) Molecules of β-catenin
E) Ribosomal RNAs

Question 17

Refer to the figure showing implantation in humans. Based on the figure, which statement is true?

A) Gene transcription can occur at points 2 and 3.
B) Point 3 is the site where implantation typically occurs.
C) Point 4 is a potential site for an ectopic pregnancy.
D) Early cleavage occurs at point 4.
E) The blastocyst typically hatches from the zona pellucida before point 3.

Question 18

The sperm contributes _______ to the zygote.

A) a nucleus only
B) half of the mitochondria and a nucleus
C) a centriole and a nucleus
D) cilium and a nucleus
E) a centrosome only

Question 19

Which statement about cleavage and early development in placental mammals is true?

A) Cells of the inner cell mass initiate implantation.
B) Premature hatching of the blastocyst from the zona pellucida can result in ectopic pregnancy.
C) Mammalian cleavage produces a blastocyst, which produces the body of the embryo, while the maternal tissues produce all the tissues of the placenta.
D) Cells of the trophoblast are pluripotent stem cells.
E) Cells derived from the trophoblast form the amnion and yolk sac.

Question 20

The gray crescent in a frog zygote

A) marks the site of important developmental events.
B) develops at the site of sperm entry.
C) causes rotation of the cortical cytoplasm.
D) does not change in position from its location in the unfertilized egg.
E) results from rotation of the heavily pigmented inner cytoplasm relative to the less pigmented cortical cytoplasm.

Question 21

Which statement about embryonic development is true?

A) Determination is the process by which blastomeres differentiate into specific cell types.
B) Preimplantation genetic diagnosis is possible in humans because they have regulative development.
C) In Drosophila, pole cells are the last cells to become determined.
D) Determination occurs later in species with mosaic development than in species with regulative development.
E) If the cells of a roundworm embryo in the two-cell stage are separated, each will develop into a complete animal.

Question 22

Which statement about animal development is true?

A) Differentiation of cells into different cell types involves signaling molecules.
B) In frog embryos, β-catenin is necessary but not sufficient for the formation of the primary embryonic organizer.
C) Blastomeres are early embryonic cells that form during gastrulation.
D) The mouth of the sea urchin forms from the blastopore.
E) Cells migrate during the blastula stage.

Question 23

Which statement about conjoined twins is true?

A) They result from the fertilization of two separate eggs.
B) They are always non-identical twins.
C) They result from the joining of trophoblasts of two separate blastocysts.
D) They usually share some organs and limbs.
E) They are often different sexes.

Question 24

Blocking the changes in shape and cell adhesion properties that lead to bottle cells would interfere with the

A) first cleavage in amphibians.
B) formation of the archenteron in sea urchins.
C) formation of the gray crescent.
D) initiation of frog gastrulation.
E) initiation of sea urchin gastrulation.

Question 25

Because the human embryo is able to split during early cleavage or blastocyst formation to produce two viable progeny, it is said to exhibit _______ development.

A) mosaic
B) determinative
C) indirect
D) regulative
E) direct

Question 26

If the endoderm cells that line the archenteron in a developing frog are altered, this will cause changes in

A) the lining of the digestive tract.
B) the sense organs.
C) structures derived from skin.
D) the heart and blood vessels.
E) muscles and bones.

Question 27

Which of these gastrulation events occurs after the others in sea urchins?

A) Changes in the shape of individual blastomeres in the vegetal hemisphere
B) Elongation of the archenteron when filopodia of secondary mesenchyme cells contract
C) Invagination
D) Formation of the archenteron
E) Formation of the mouth

Question 28

A researcher working with developing fruit flies wants to produce a fly without gametes.Which element should be targeted for destruction in the early embryo prior to gastrulation in order to achieve this?

A) Pole plasm
B) The group of nuclei at the anterior pole of the egg
C) Ectoderm
D) Anterior-most cells of the blastoderm
E) Ventral cytoplasm of the syncytium

Question 29

If the dorsal lip of the blastopore is transplanted from one frog gastrula onto a second frog gastrula on the opposite side from the embryo's original blastopore, which result is the most likely?

A) A belly piece will form.
B) Gastrulation will cease.
C) A second complete embryo will form belly-to-belly with the recipient of the transplant.
D) The transplant will be rejected.
E) Only half an embryo will develop at the site of transplantation.

Question 30

Formation of the endoderm and mesoderm during gastrulation in frogs results from

A) involution.
B) migration of cells that have broken free within the blastocoel.
C) formation of columnar cells at the vegetal pole.
D) invagination.
E) migration of secondary mesenchyme cells.

Question 31

Refer to the figure showing stages of gastrulation in the frog. Which of the following represents the correct sequence of events?

A) A, B, C, D
B) A, C, B, D
C) C, D, B, A
D) D, A, C, B
E) D, C, A, B

Question 32

Refer to the figure showing implantation in humans. Based on the figure, which statement is true?

A) The embryo proper develops from the structure at point 8.
B) The stage of embryonic development depicted is early cleavage.
C) The structure at point 7 secretes proteolytic enzymes that aid implantation.
D) The structure at point 8 is formed when cells of the structure at point 6 secrete fluid.
E) The structure at point 10 develops from the structure at point 9.

Question 33

The mesoderm

A) is located on the outside of the embryo.
B) is found in blastula-stage embryos.
C) lies between the endoderm and the ectoderm.
D) gives rise to the lining (inner epithelium) of the gut.
E) is formed during cleavage.

Question 34

Gastrulation is the stage of development

A) when neural tube formation is completed.
B) that makes possible the inductive interactions that trigger differentiation and organ formation.
C) that follows the formation of the three germ layers.
D) that precedes cleavage.
E) that is marked by a dramatic increase in the rate of mitosis.

Question 35

An ectopic (tubal) pregnancy in a human occurs when the blastocyst

A) fails to hatch from the zona pellucida.
B) hatches too early from the zona pellucida.
C) hatches too late from the zona pellucida.
D) implants close to the cervix.
E) lacks a trophoblast.

Question 36

After gastrulation, the mesodermal cells contribute to the developing

A) brain.
B) bones.
C) lining of the digestive tract.
D) epidermis.
E) liver epithelium.

Question 37

If a researcher inhibited formation of filopodia during sea urchin gastrulation, which of the following would be least likely to form?

A) Anus
B) Primary mesenchyme
C) Secondary mesenchyme
D) Mouth
E) Blastopore

Question 38

Whereas _______ contributes to the _______, _______ contributes to the _______.

A) endoderm; lining of the respiratory tract; ectoderm; heart muscles
B) endoderm; nervous system; mesoderm; bones and muscles
C) ectoderm; teeth; endoderm; dermal layer of the skin
D) endoderm; lining of the digestive tract; mesoderm; epidermis
E) ectoderm; nervous system; mesoderm; bones and muscles

Question 39

After gastrulation, the endodermal cells contribute to the developing

A) hair, nails, and sweat glands.
B) blood vessels.
C) lining of the digestive and respiratory tracts.
D) heart.
E) skin.

Question 40

After gastrulation, the ectodermal cells contribute to the developing

A) sense organs and epidermis.
B) skeletal muscles.
C) inner lining of the respiratory tract.
D) pancreas.
E) heart muscles.

Question 41

Which statement about events during the neurulation stage of development is true?

A) Neurulation is the first stage in gastrulation.
B) The notochord organizes overlying ectoderm.
C) The anterior end of the notochord becomes the brain.
D) The likelihood of a neural tube defect is lowered if a pregnant woman restricts her intake of folic acid.
E) The notochord is a neural structure.

Question 42

Which is a shared feature of the embryonic development of chicks and placental mammals?

A) Cells migrate through a midline primitive groove during gastrulation.
B) The body of the embryo forms on top of a large yolk mass.
C) The hypoblast forms when cells of the blastodisc break free and form a continuous layer below the blastocoel.
D) Hensen's node forms the neural tube.
E) The hypoblast forms the body of the embryo.

Question 43

Which characterizes development in placental mammals but not birds?

A) Epiblast cells migrate through the primitive groove to become endoderm and mesoderm.
B) The embryo proper forms from the epiblast.
C) The hypoblast contributes to extraembryonic membranes.
D) Signaling molecules in Hensen's node are similar to those found in the frog organizer.
E) Cleavage produces a blastocyst with an inner cell mass.

Question 44

Refer to the figure showing a stage of gastrulation in the frog. If a piece of ectoderm destined to be epidermis (outer layer of skin) is removed from a gastrula of the stage seen in the figure and put into a location destined to be neural tissue in a similarly aged gastrula, which result is the most likely?

A) The transplanted tissue will develop into neural tissue.
B) The transplanted tissue will develop into dermis.
C) The transplant will be rejected.
D) The transplanted tissue will develop into epidermis.
E) A second complete embryo will form belly-to-belly with the recipient of the transplant.

Question 45

Refer to the figure showing a stage of gastrulation in the frog. Consider a piece of ectoderm that is destined to be neural tissue in its original location in the gastrula shown in the figure.If it is transplanted into a location destined to be epidermis in a gastrula of similar age, which of the following will result?

A) The transplanted tissue will develop into neural tissue.
B) The transplanted tissue will develop into dermis.
C) The transplant will be rejected.
D) The transplanted tissue will develop into epidermis.
E) A second complete embryo will form belly-to-belly with the recipient of the transplant.

Question 46

Along the dorsal surface of the frog embryo, mesoderm cells secrete BMP proteins, which induce the overlying ectoderm to become epidermis.If the actions of BMP proteins were blocked,

A) the ectoderm would develop into bone tissue.
B) the ectoderm would develop into neural tissue.
C) gastrulation would cease.
D) a second entire embryo would develop along the embryo's dorsal surface.
E) the ectoderm would develop into the lower skin layer (dermis).

Question 47

Which is the correct matching of term and definition as they relate to gastrulation in frogs?

A) Involution-process by which surface cells change their shape in order to invaginate into the blastocoel
B) Bottle cells-cells in the gray crescent region that bulge inward while remaining attached to the outer surface of the blastula
C) Epiboly-process by which vegetal hemisphere cells flatten and move inward
D) Blastocoel-fluid-filled cavity that enlarges as the archenteron enlarges
E) Dorsal lip of the blastopore-cells that form the neural tube of the embryo

Question 48

If a researcher studying amphibian development blocked the secretion of BMP proteins by mesoderm under the embryo's dorsal surface, the likely result would be that the

A) overlying ectoderm would become epidermis.
B) overlying ectoderm would become dermis.
C) overlying ectoderm would become neural tissue.
D) underlying endoderm would form neural tissue.
E) underlying endoderm would form dermis.

Question 49

In which way does the notochord differ from the neural tube?

A) The notochord develops from endoderm, whereas the neural tube develops from ectoderm.
B) The neural tube forms the brain and spinal cord, and the notochord serves as a support structure and major organizer for the embryo.
C) Development of the neural tube characterizes all vertebrate embryos, whereas development of the notochord is restricted to amphibians.
D) During gastrulation, the neural tube forms first, followed by formation of the notochord.
E) The neural tube forms the spinal cord, and the notochord forms the vertebrae that surround and protect the spinal cord.

Question 50

Experimental destruction of cells of the hypoblast of a developing chick would most immediately impair

A) formation of the primitive groove.
B) movement of surface cells into the gastrula.
C) cleavage.
D) formation of the blastocoel.
E) formation of extraembryonic membranes.

Question 51

In birds and placental mammals, the embryo proper forms from the

A) trophoblast.
B) chorion.
C) amnion.
D) epiblast.
E) hypoblast.

Question 52

Experimental depletion of β-catenin mRNA transcripts in amphibian embryos results in

A) failure of cleavage to occur.
B) induction of a second axis of embryo formation.
C) failure of gastrulation to occur.
D) failure of invagination to occur.
E) slowing down of the cleavage process.

Question 53

In the developing chick, the _______ and _______ perform functions equivalent to those of the _______ and _______, respectively, in the developing frog.

A) hypoblast; epiblast; blastopore; dorsal lip of the blastopore
B) primitive groove; Hensen's node; blastopore; dorsal lip of the blastopore
C) blastodisc; yolk mass; blastopore; dorsal lip of the blastopore
D) primitive groove; Hensen's node; dorsal lip of the blastopore; blastodisc
E) primitive groove; Hensen's node; blastodisc; dorsal lip of the blastopore

Question 54

Which statement about early development in vertebrates is true?

A) Failure of the neural folds to fuse in the anterior region of the developing neural tube results in anencephaly.
B) Gastrulation follows organogenesis.
C) The notochord is formed from neural ectoderm and provides structural support to the developing embryo.
D) Neural crest cells form the neural tube.
E) Failure of the neural folds to fuse in the posterior region of the developing neural tube is often linked to a deficiency in vitamin D.

Question 55

As in chick development, in humans the amnion forms from the

A) hypoblast.
B) epiblast.
C) chorion.
D) trophoblast.
E) yolk sac.

Question 56

Refer to the figure showing a stage of gastrulation in the frog. Consider a piece of ectoderm that is destined to be neural tissue in its original location in the gastrula shown in the figure.If it is transplanted into a location destined to be epidermis in a gastrula of similar age, which of the following will result?

A) The transplanted tissue will develop into neural tissue.
B) The transplanted tissue will develop into dermis.
C) The transplant will be rejected.
D) The transplanted tissue will develop into epidermis.
E) A second complete embryo will form belly-to-belly with the recipient of the transplant.

Question 57

In both birds and mammals, gastrulation occurs in the

A) hypoblast.
B) epiblast.
C) blastodisc.
D) trophoblast.
E) blastocyst.

Question 58

The structure in birds and placental mammals that is most equivalent to the dorsal lip of the frog blastopore is

A) the primitive groove.
B) the archenteron.
C) the yolk plug.
D) Hensen's node.
E) the epiblast.

Question 59

If cells from the presumptive neural ectoderm of a late frog gastrula are transplanted onto the surface of a second late frog gastrula where skin would normally develop, the transplanted cells will still develop into neural tissue.This experiment shows that the transplanted cells are

A) differentiated.
B) totipotent.
C) discontinuous.
D) determined.
E) endodermal.

Question 60

Experimental overexpression of β-catenin in another region of an amphibian embryo results in

A) failure of cleavage to occur.
B) induction of a second axis of embryo formation.
C) failure of gastrulation to occur.
D) failure of invagination to occur.
E) speeding up of the cleavage process.

Question 61

The cells from the most lateral portions of the neural plate become migratory cells

A) that form epidermis.
B) known as neural crest cells.
C) that form the neural tube.
D) that form the neural groove.
E) that form somites.

Question 62

An embryo exhibits abnormal development in the most posterior part of its body.The responsible Hox gene is located

A) close to the 3′ end of the Hox gene complex.
B) at the 5′ end of the Hox gene complex.
C) in the middle of the Hox gene complex.
D) at the 3′ end of the Hox gene complex.
E) in another gene complex.

Question 63

The extraembryonic membranes in an amniote allow the embryo to develop within a shell on land.What do these membranes allow the embryo to do that an amphibian embryo is unable to do?

A) Store urinary waste
B) Obtain nutrients from yolk
C) Exchange gasses with the environment
D) Be suspended in a liquid environment
E) Develop vascularization before hatching

Question 64

The gene Hoxb1 is close to the 3ʹ end of a Hox gene complex.Where in a vertebrate embryo might expression of Hoxb1 occur?

A) Anterior portion
B) Middle portion
C) Posterior portion
D) Along the entire length of the embryo
E) On the ventral surface

Question 65

Imagine looking at a slide containing a cross section of a frog embryo that has just completed neurulation.If you begin your examination at the dorsal surface of the embryo and moved inward, you will see, in sequence,

A) epidermis, notochord, neural tube, and gut.
B) epidermis, neural tube, gut, and notochord.
C) neural tube, epidermis, notochord, and gut.
D) epidermis, neural tube, notochord, and gut.
E) notochord, neural tube, gut, and epidermis.

Question 66

In each somite there are several regions of cells that give rise to different structures.Experimental destruction of one somite would impair the development of

A) muscles, cartilage of vertebrae, and the inner layer of skin (dermis).
B) the lining of the reproductive tract and lungs.
C) the pancreas and lungs.
D) pigment cells, the jaw, and smooth muscle.
E) the brain, skull, and dermis of the face.

Question 67

The mesoderm of the anterior part of a vertebrate embryo is programmed to produce forelegs rather than hind legs by

A) convergent extension.
B) neural crest cells.
C) Hox genes.
D) the spacing of somites in the embryo.
E) the archenteron.

Question 68

Which statement about Hox genes is true?

A) In mammals, the temporal and spatial expression of Hox genes follows their linear order on the chromosome.
B) Most but not all Hox genes contain a sequence of DNA called the homeobox.
C) Hox gene products serve as structural proteins.
D) In vertebrates, Hox genes control differentiation primarily along the dorsal-ventral axis.
E) Mammals have ten Hox gene complexes, each with about four genes.

Question 69

If an embryo exhibits abnormal development of peripheral nerves, the source of the problem is most likely damage or impairment of

A) the neural tube.
B) neural crest cells.
C) endoderm.
D) somites.
E) the notochord.

Question 70

Imagine looking at a slide of a cross section of a frog embryo that has just completed neurulation.Which is the sequence of structures you should see, beginning with inside the gut of the embryo and moving outward?

A) Gut endoderm, epidermis, notochord, neural tube
B) Gut ectoderm, notochord, neural tube, epidermis
C) Gut endoderm, neural tube, epidermis, notochord
D) Gut ectoderm, epidermis, neural tube, notochord
E) Gut endoderm, notochord, neural tube, epidermis

Question 71

A body plan consisting of repeating segments that are modified during development into structures such as vertebrae, ribs, and muscles depends on the production of cells by

A) the neural tube.
B) neural crest cells.
C) endoderm.
D) somites.
E) the notochord.

Question 72

Neural tube defects during development

A) are more common in echinoderms than in vertebrates.
B) occur during mosaic development.
C) are linked to folic acid deficiency in the diets of pregnant women.
D) have increased significantly in the United States in the last 100 years.
E) are due to genetic but not environmental factors.

Question 73

Which statement about neural crest cells is true?

A) Neural crest cells give rise to the central nervous system.
B) Body segmentation develops because of migration of neural crest cells.
C) Neural crest cells are derived from the epidermal ectoderm.
D) Neural crest cells are migratory.
E) Neural crest cells form the brain and spinal cord.

Question 74

Somites are derived from

A) mesoderm.
B) the neural crest.
C) ectoderm.
D) endoderm.
E) neural tissue.

Question 75

Which is the typical chronological order in which structures appear during neurulation in the anterior region of an amphibian embryo?

A) Neural folds, neural plate, deep neural groove, neural tube
B) Neural plate, neural folds, deep neural groove, neural tube
C) Deep neural groove, neural folds, neural tube, neural plate
D) Neural folds, deep neural groove, neural tube, neural plate
E) Deep neural groove, neural folds, neural plate, neural tube

Question 76

Neural crest cells will become many different cell types in many different structures, including

A) ribs.
B) trunk muscles.
C) lower layer (dermis) of the skin.
D) peripheral nerves.
E) vertebrae.

Question 77

Which structure(s) would be directly impaired by experimental destruction of somites?

A) Vertebrae
B) Pancreas
C) Lungs
D) Epidermis
E) Stomach

Question 78

If you experimentally delete one somite from the right side of a developing chick embryo, which of the following will likely be affected in the chick when it hatches?

A) Left region of the brain
B) Peripheral nerves in one region on the right side
C) Notochord in the region of the deleted somite
D) Muscles and ribs in one region on the left side
E) Right chambers of the heart

Question 79

Approximately how many different Hox genes do mammals possess?

A) 4
B) 10
C) 40
D) 400
E) 4,000

Question 80

The order in which mammalian Hox genes are expressed during development

A) varies with developmental age.
B) depends on circulating hormone levels.
C) proceeds from the posterior to the anterior parts of the embryo.
D) reflects the linear order in which they appear on their chromosomes.
E) determines the dorsal-ventral organization of the embryo.