Deck 21: Animal Development

Question 1

Of the main processes in embryogenesis, which begins first?

A) Cell differentiation
B) Cell proliferation
C) Cell migration
D) Morphogenesis
E) Programmed cell death

Answer 1

Cell proliferation

Question 2

During cleavage, the

A) total amount of cytoplasm in the embryo decreases.
B) nucleus-to-cytoplasm ratio decreases.
C) nucleus-to-cytoplasm ratio increases.
D) the size of blastomer increases.
E) nucleus-to-cytoplasm ratio remains constant.

Answer 2

nucleus-to-cytoplasm ratio increases.

Question 3

During cleavage, cell division is rapid because

A) cells undergo mitosis without any intervening synthesis of DNA.
B) the G₁ and G₂ phases of the cell cycle may be virtually eliminated.
C) the S phase is reduced in time.
D) components of the spindle are more rapidly synthesised.
E) the presence of yolk speeds up cytokinesis.

Answer 3

the G₁ and G₂ phases of the cell cycle may be virtually eliminated.

Question 4

In animal development, cleavage refers to

A) the dissolving of the egg jelly coat by acrosomal enzymes.
B) the splitting of the mesoderm to form a central, fluid-filled cavity.
C) a series of mitotic divisions of the zygote without any decrease in cell size.
D) a series of mitotic divisions of the zygote without any increase in embryo size.
E) production of blastomeres resulting in increased size of the embryo.

Question 5

If a zygote has a high concentration of yolk that is unevenly distributed, then cytokinesis

A) takes place throughout the embryo, but cleavage divisions proceed more slowly in the vegetal region.
B) takes place throughout the embryo, but cleavage divisions proceed more slowly in the animal region.
C) takes place throughout the embryo, and cleavage divisions proceed at about the same rate in all parts of the embryo.
D) is confined to the yolk and produces a disc of cells between the yolk and the cavity.
E) is confined to the yolk-free portion of the zygote.

Question 6

Which of the following statements about early development in marsupials is CORRECT?

A) The eggs of marsupials are virtually yolk-free, so the blastomeres are all of a similar size.
B) The tissues of the embryo proper are derived from a specific set of blastomeres, clustered together to form an inner cell mass, at one end of the blastula.
C) The first cleavage division is vertical, but the second cleavage division is horizontal in one blastomere and vertical in the other.
D) The egg is surrounded by external envelopes, which are porous to uterine secretions that nourish the embryo until it implants.
E) The egg is yolk rich and the first three divisions are unequal.

Question 7

A blastula that is spherical in shape, with blastomeres of approximately equal size in a single layer around the central blastocoel, is most likely to be that of a

A) frog.
B) bird.
C) sea urchin.
D) marsupial.
E) mouse.

Question 8

During gastrulation the blastocoel becomes

A) the coelom.
B) the archenteron.
C) the blastopore.
D) filled with the hypoblast.
E) obliterated.

Question 9

Nervous tissue forms from

A) ectoderm.
B) mesoderm.
C) endoderm.
D) a combination of ectoderm and mesoderm.
E) coelom.

Question 10

You observe an animal embryo that is spherical in shape. Transverse sections through the embryo show that the outer wall consists of three layers of cells, and that there is a single axis of symmetry. The interior of the embryo is a fluid-filled cavity. The most recent developmental process to affect this embryo directly was

A) organogenesis.
B) gastrulation.
C) cleavage.
D) morphogenesis.
E) neurulation.

Question 11

You observe an animal embryo that is more-or-less spherical in shape. Projecting from the surface along one 'side' of the embryo is a pair of ridges, separated by a shallow groove. A transverse section through the embryo, perpendicular to these ridges, shows that the interior of the embryo is a fluid-filled cavity, and that the body wall consists of three layers of cells. This embryo is undergoing

A) neurulation.
B) gastrulation.
C) morphogenesis.
D) involution.
E) cleavage.

Question 12

In animal development, the formation of complex three-dimensional organs involves a number of morphogenetic processes. These include
1)localised cell proliferation
2)migration of individual cells to new sites
3)thickening and infolding of epithelial sheets
4)programmed death of localised groups of cells
5)disaggregation of tissues into individual cells.
Which of the following lists these processes, in the order they are likely to begin, during normal embryonic development of a limb bud in mammals or birds?

A) 5, 2, 1, 3, 4
B) 2, 3, 5, 4, 1
C) 3, 1, 5, 2, 4
D) 1, 5, 2, 4, 3
E) 2, 1, 5, 3, 4

Question 13

Which of the following terms is inclusive of the others?

A) Organogenesis
B) Neurulation
C) Morphogenesis
D) Cellular differentiation
E) None of the answers are correct

Question 14

Which of the following types of stem cells have the potential to give rise to the greatest variety of different cell types?

A) Neural stem cells.
B) Uncommitted haemopoietic stem cells.
C) Embryonic stem cells.
D) Lymphocyte stem cells.
E) Committed haematopoietic stem cells.

Question 15

In an experiment on an early frog embryo, cells from the region that will eventually form the neural plate were transplanted to another part of the blastula. It was noticed that the transplanted tissue formed a second neural plate later in the embryo's development. The best explanation for this observation is that

A) the cells in the transplanted tissue had already differentiated.
B) cells surrounding the transplanted tissue at the new site influenced the tissue to differentiate.
C) biochemical activity within the transplanted cells had already determined which developmental genes would be activated.
D) the tissue underwent a transplant shock that caused it to differentiate.
E) all cells are committed to a specific terminal cell.

Question 16

Mammalian embryos can develop normally despite having some blastomeres removed during early cleavage because

A) in the development of mammals, intercellular signalling is of more importance than cytoplasmic signalling.
B) maternal factors present within the zygote have no influence on the development of mammalian embryos.
C) cell-cell signalling does not become important in mammalian development until after the formation of the blastula.
D) mammalian blastomeres remain unipotent throughout the early stages of cleavage.
E) embryonic stem cells are pluripotent.

Question 17

Genomic equivalence is exhibited when all

A) genes in an organism are equal.
B) cells in an organism have the same genome.
C) cell lineages in an organism show similar loss of genetic information during development.
D) All of the answers are correct.
E) None of the answers are correct.

Question 18

Drosophila melanogaster is a useful species for the study of developmental genes because

A) Drosophila are easily bred and raised a laboratory.
B) the Drosophila genome has been well studied.
C) Drosophila has a fast generation time.
D) many mutant Drosophila are available.
E) All of the answers are correct.

Question 19

Maternal-effect genes are

A) transcribed and translated in the embryo.
B) transcribed and translated during oogenesis.
C) transcribed during oogenesis and translated during embryonic development.
D) transcribed during oogenesis and translated prior to fertilisation.
E) transcribed during oogenesis and translated during organogenesis.

Question 20

Mutations in maternal-effect genes are readily identified because

A) heterozygous mutant individuals are produced from homozygous mutant mothers.
B) homozygous mutant individuals from heterozygous parents can develop, but eggs laid by homozygous mutant females cannot develop.
C) heterozygous mutant individuals from homozygous parents can only develop normally if the mother is homozygous mutant.
D) heterozygous mutant females produce eggs that are not capable of normal development.
E) homozygous mutant individuals do not develop and are embryonic lethal.

Question 21

In a cross between a female Drosophila homozygous for a recessive mutant maternal-effect gene (m^-/m^-) and a wild-type male (m⁺/m⁺), the percentage of progeny that show normal development will be

A) 0 per cent.
B) 25 per cent.
C) 50 per cent.
D) 75 per cent.
E) 100 per cent.

Question 22

In Drosophila, a bicoid egg

A) will develop into a larva with two heads.
B) will develop into an adult without a head or a thorax.
C) will develop into an embryo without a head or thorax region.
D) has two nuclei.
E) will not develop into a syncytium.

Question 23

In animal development, zygotic genes

A) belong to the egg nucleus.
B) belong to the sperm nucleus.
C) are part of the zygote genome.
D) are found in the cytoplasm of the zygote.
E) are inherited only from the mother.

Question 24

Developmental regulatory molecules that act in a concentration-dependent fashion are called

A) anterior determinants.
B) ligands.
C) homeodomain proteins.
D) morphogens.
E) polarity genes.

Question 25

The following groups of mutants developed from mutations in genes active during the development of Drosophila. Based on the characteristics of the mutants, which group resulted from mutations in the earliest-acting gene?

A) Mutants with half the normal number of body segments
B) Mutants in which cells that would normally become epidermal cells developed into nerve cells
C) Mutants that have kinky bristles instead of the long, curled bristles of normal flies
D) Mutants without body segments
E) Mutants with tail structures at both ends

Question 26

Which of the following mutant Drosophila phenotypes resulted from a mutation in a maternal gene?

A) An embryo with half the normal number of body segments
B) An embryo that lacks several abdominal segments
C) An embryo without head segments
D) Mutants with antennae attached to the posterior
E) An embryo with a pair of legs instead of antennae attached to the head

Question 27

Which of the following mutant Drosophila phenotypes resulted from a mutation in a pair-rule gene?

A) An embryo with half the normal number of body segments
B) An embryo that lacks several abdominal segments
C) An embryo without head segments
D) An embryo with antennae attached to the posterior
E) An embryo with a pair of legs instead of antennae attached to the head

Question 28

In Drosophila, mutations in homeotic genes can lead to

A) the polarity of segments being reversed.
B) segments missing.
C) segments of one body part being transformed into another.
D) determine the distance between the anterior and posterior of the embryo.
E) reversal of the dorso-ventral axis.

Question 29

Transcription factors are

A) mRNA products of maternal genes that are transcribed during oogenesis and translated after fertilisation.
B) cytoplasmic determinants that are transcribed in the zygote and segregated into particular blastomeres during cleavage.
C) proteins that regulate the transcription of other genes during development.
D) genes that control the expression of other genes.
E) All of the answers are transcription factors.

Question 30

Hox genes

A) are transcriptional regulators.
B) produce proteins which repress different genes in different segments.
C) expression is regulated by the segmentation genes.
D) produce proteins which contain a DNA binding sequence.
E) All of the answers are correct.

Question 31

When cells cease dividing during development, they are

A) terminally differentiated.
B) stem cells.
C) undergoing apoptosis.
D) pluripotent.
E) embryonic.

Question 32

Gastrulation

A) in Xenopus is by simple invagination which results in a new cavity, the archenteron.
B) requires a rapid series of mitotic cell division resulting in asymmetric cells.
C) involves thickening and folding of epithelial sheets, migration of disaggregated cells and apoptosis of random cells.
D) results in the formation of the germ cell layers and body cavities.
E) is not influenced by the structure of the embryo.

Question 33

Morphogenic changes during organogenesis are generated by

A) thickening and folding of epithelial sheets.
B) disaggregation of tissues into individual cells.
C) cell migration.
D) localised apoptosis.
E) All the answers are correct.

Question 34

A maternal-effect gene is

A) when developmental phenotype is determined by the genotype of the mother.
B) a gene which produces a product which controls dorsal-ventral division of the embryo.
C) a gene which influences the polarity in Drosophila development.
D) a gene product which acts in a concentration dependent manner to direct morphogenesis.
E) All of the answers are correct.

Question 35

The order of embryo development is

A) zygote $\rightarrow$ cleavage $\rightarrow$ organogenesis $\rightarrow$ gastrulation.
B) fertilisation $\rightarrow$ gastrulation $\rightarrow$ blastula $\rightarrow$ organogenesis.
C) fertilisation $\rightarrow$ cleavage $\rightarrow$ zygote $\rightarrow$ blastula.
D) fertilisation $\rightarrow$ zygote $\rightarrow$ blastula $\rightarrow$ neurulation.
E) zygote $\rightarrow$ morphagenesis $\rightarrow$ blastula $\rightarrow$ gastrulation.

Question 36

In addition to organogenesis, many animals undergo a further stage of development called

A) post-embryonic neurulation.
B) proliferation.
C) bilateral symmetrification.
D) rostral neuroporosis.
E) metamorphosis.

Question 37

You are listening to a debate on the processes of neurulation in mammals compared to fishes. Both speakers agree that in fish, neurulation involves cells from either side of the midline coming together completely to form a seam, as opposed to most other vertebrates whereby two neural folds rise upwards on either side of a neural groove and then fold towards each other and meet to form a tube. Speaker one asserts that in fish, because of the morphology of the resulting structure, this processes produces a 'neural keel', whereas speaker two states that this process results in a 'neural tube'. Which speaker, if any, is correct?

A) Neither, neurulation in fish at this developmental stage produces a neural plate
B) Neither, neurulation in fish at this developmental stage produces a neural groove
C) They are both correct - either term is acceptable
D) Speaker one
E) Speaker two

Question 38

Which of the following is NOT a process involving epithelial to mesenchymal transition?

A) Migration of neural crest cells away from the neural tube
B) The detachment and migration of epithelial cells
C) Delamination of primary mesenchyme cells during sea urchin gastrulation
D) Metastasis of epithelial tumours
E) Formation of the central lumenal space

Question 39

With regard to animal development, what is a somite?

A) Segmentally random blocks of mesoderm situated in the centre of a fully developed neural tube
B) All of the options listed are incorrect
C) Repeated subunits of the dermomyotome
D) A partially differentiated region of sclerotome
E) Alpha-linked 1-3- $\beta$ -arabinoxylans that arise around the margins of a developing neural plate

Question 40

A stem cell that can give rise to only one type of differentiated cell is called unipotent. By an extension of this nomenclature logic, what would be the term given to a stem cell that can give rise to many cell types?

A) Bipotent
B) Alphapotent
C) Radial-potent
D) Megapotent
E) Multipotent

Question 41

Cells produced specifically during cleavage are called

A) blastocoels.
B) embryos.
C) stem cells.
D) blastomeres.
E) gametes.

Question 42

During gastrulation, three different cell layers become apparent. One of these is the ectoderm (ecto = outer, dermis = skin). Immediately within the ectoderm is the mesoderm. As ecto = outer, and endo = inner, what would be the term given to the cell layer folded within the invaginating vegetal plate?

A) Endocarp
B) Endoderm
C) Endoform
D) Endochyma
E) All of the options listed are incorrect

Question 43

Cell shape is a common feature during the process of morphogenesis. Which of the components of the cytoskeleton is the most important in driving cell morphology changes during this developmental stage?

A) Microfilaments
B) Microtubules
C) Actin filaments
D) Intermediate filaments
E) All of the cytoskeletal structural proteins are equally important during morphogenesis

Question 44

Haematopoietic stem cells give rise to

A) haemoglobin.
B) blood cells.
C) totipotent cells.
D) odour receptor cells.
E) topoietic cells in the bone marrow.