Deck 21: Principles of Development

Question 1

What is common to gap genes,segment-polarity genes,and homeotic genes?

A)They act independently of one another.
B)They code for transcription regulatory factors.
C)They can be activated at any time during development.
D)They are unique to Drosophila embryos.

Answer 1

B

Question 2

Gastrulation is an important event in early embryonic development.Which of the following is NOT a result of this process?

A)formation of three embryonic cell layers
B)movement and alignment of many embryonic cells
C)determination of cell types as a result of cell-cell interactions
D)formation of specialized plant tissues

Answer 2

D

Question 3

Even though plant and animal development processes share a number of features,there are some differences between the two groups of organisms.Which of the following is NOT a shared characteristic of plant and animal development?

A)Gene expression in developing embryonic tissues is closely regulated.
B)Orientation of cells and tissues is critical for proper development.
C)Differentiation of cells is directed and maintained by cascades of signals.
D)Cell types,once determined,generally cannot change their differentiated characteristics.

Answer 3

D

Question 4

Suppose the pair-rule genes were inactivated in Drosophila embryos.What is the likely result of the experiment?

A)The embryos would develop normally.
B)The embryos would lack several segments.
C)The embryos would have impaired anterior-posterior polarity.
D)The embryos would have missing alternate segments.

Question 5

When the Bicoid protein is expressed in Drosophila,the embryo is still syncytial (divisions between cells are not yet fully developed).This helps to explain which observation by Nüsslein-Volhard and Wieschaus?

A)mRNA from the egg is translated into the Bicoid protein.
B)Bicoid protein diffuses throughout the embryo in a concentration gradient.
C)Bicoid protein serves as a transcription regulator.
D)Bicoid protein determines the dorsoventral axis of the embryo.

Question 6

The protein of the bicoid gene in Drosophila determines

A)the anterior-posterior axis of the embryo.
B)the ventral-lateral axis of the embryo.
C)the medial-lateral axis of the embryo.
D)the number of segments in the embryo.

Question 7

Which of the following would constitute evidence that differentiated cells retain all the genes of developing cells?

A)Developing cells have many mRNA transcripts that can hybridize with DNA from mature cells.
B)Differentiated cells generally synthesize a specific group of proteins.
C)Nuclei from mature cells can direct the development of an entire individual.
D)Differentiated cells lose their polarity if removed from the organism.

Question 8

Modern cloning techniques have demonstrated that the vast majority of differentiated cells are genetically equivalent to developing cells in the embryo.What is an exception to this finding?

A)Nerve cells are often limited in their mitotic activity.
B)In the immune system,sequences of DNA may rearrange to permit response to new pathogens.
C)In the brain,DNA sequences may change with learned behavior.
D)The lining of the digestive system is frequently replaced.Some of these cells may show repeats of certain DNA sequences.

Question 9

Cellular differentiation is usually produced by

A)differences in gene expression.
B)differences in DNA sequences.
C)differences in gene copy numbers.
D)morphogenesis.

Question 10

One form of programmed cell death is apoptosis.In which developmental situation would you predict apoptosis would NOT play a major role?

A)growth of nerves and blood vessels into a body segment
B)sculpting of digits in the developing hindlimb
C)growth of the atrial septum in the four-chambered mammalian heart
D)disappearance of the embryonic tail in developing humans

Question 11

When is a cell considered differentiated?

A)when a cell first becomes irreversibly committed to a particular fate
B)when a cell begins its pattern formation
C)when a cell manufactures proteins that are specific to a particular cell type
D)when a cell is part of recognizable tissues or organs

Question 12

Suppose the protein specified by bicoid were injected into Drosophila embryos,so that a high concentration was present everywhere in the embryo.What might be the result of such an experiment?

A)The embryos would grow larger than normal.
B)The embryos would show no development of posterior regions.
C)The embryos would show no development of anterior regions.
D)The embryos would halt their development.

Question 13

Cloning of plants from cuttings demonstrates that

A)genetic information is lost during plant development.
B)differentiated cells may contain embryonic mRNAs.
C)plants can reverse the differentiation process.
D)genetic information is retained in mature plant cells.

Question 14

Suppose you found several Drosophila mutants that possessed additional legs growing out of the head segments.The probable mutation would be found in

A)segment-polarity genes.
B)gap genes.
C)pair-rule genes.
D)homeotic genes.

Question 15

During Drosophila development,there is a regulatory cascade of gene activation.The proper sequence for this cascade is

A)bicoid,gap genes,pair-rule genes,and segment polarity genes.
B)bicoid,pair-rule genes,gap genes,and segment polarity genes.
C)bicoid,segment-polarity genes,gap genes,and pair-rule genes.
D)bicoid,gap genes,segment polarity genes,and pair-rule genes.

Question 16

Communication within and between cells of an embryo can include all of the following except

A)increased concentration of signaling molecules.
B)changes in binding to regulatory sequences.
C)changes in gene transcription.
D)changes in gene sequences.

Question 17

In combination,what do the products of gap genes,pair-rule genes,and segmentation polarity genes of fruit flies do?

A)They trigger the reorganization of the larval body into an adult body.
B)They define the segmented body plan of the embryo.
C)They set up the back-to-belly axis of the larval body.
D)They direct cell movements during differentiation.

Question 18

Suppose there was a mutation in the segment-polarity genes of Drosophila.What do you suppose might be the outcome?

A)Several segments of the embryo will be missing.
B)Every other segment of the embryo will be missing.
C)Legs will appear in the place of antennae.
D)Antennae will appear in a different part of their usual segment.

Question 19

Gene expression in developing organisms is regulated on several different levels.In many developing animals,regulation of gene expression is influenced by the action of Hox genes.Which of the following regulatory elements are produced by many Hox genes?

A)transcriptional factors
B)cell surface molecules for cell-cell interactions
C)signals from maternal cytoplasm,such as bicoid
D)mRNA processing factors

Question 20

What was the experimental focus of the preliminary genetic screening performed by Nüsslein-Volhard and Wieschaus?

A)to evaluate the mutagenic properties of varied treatments
B)to discover the bicoid gene
C)to generate two-tailed fruit-fly embryos
D)to identify fruit flies with mutations in genes that control fruit-fly development

Question 21

Animal species exhibit an enormous diversity of genetic information contained in nuclear DNA.This may be reflected in very different genome sizes.One might predict that animals with more complex structures might show greater numbers of different types of mRNAs during development.Scientists investigating this possibility were surprised to find that similar numbers of genes were transcribed at a particular time in development among species whose genomes differed greatly in size.How can this result be interpreted?

A)Some species retain large amounts of DNA that are never used.
B)The number of genes transcribed at any one time is tightly regulated and independent of genome size.
C)Genome size has nothing to do with the physical complexity of the species.
D)Nuclear DNA complexity is unrelated to the complexity of mRNAs transcribed during development.

Question 22

During development,what a cell differentiates into depends in part on its location along three body axes.Which axis runs towards the organism's head?

A)dorsal
B)anterior
C)posterior
D)ventral

Question 23

What does the term "genetic equivalence" refer to?

A)Plant cells can differentiate into animal cells and vice versa.
B)Differentiated cells of a plant contain the same genes as other cells in the same plant.
C)Differentiated animal cells can share gene products with each other,resulting in a balance of products among the cells.
D)During development,sending and receiving of signals via cell-cell interactions makes the cells involved more equal.

Question 24

All of the following are true of embryonic stem cells except that

A)they can be found in human blastocysts.
B)they retain the potential to become different types of cells.
C)they continue to undergo mitosis when most cells have stopped dividing.
D)they are terminally differentiated.

Question 25

Which of the following human cells contains the gene for alcohol dehydrogenase,a liver enzyme that processes alcohol?

A)sperm and egg cells
B)liver cells
C)heart cells
D)Only the cells in A and B contain the gene for this enzyme.
E)All of the cells in A,B,and C contain the gene for this enzyme.

Question 26

During development,what a cell differentiates into depends in part on its location along three body axes.Which axis runs towards the organism's belly?

A)dorsal
B)anterior
C)posterior
D)ventral

Question 27

Which of the following is not an example of the process of apoptosis during organ and tissue development?

A)Death of cells between the toes in chicken embryos.
B)Leaves falling off trees in the fall.
C)Petals falling off flowers after pollination.
D)Lou Gehrig's disease

Question 28

Cellular differentiation results from

A)changes in the genetic makeup of cells.
B)differential gene expression.
C)mutations in DNA.

Question 29

Evolutionary theory has until recently stressed genetic mutations that alter protein amino acid sequences as the major source of variation that leads to speciation.Evo-devo (evolutionary developmental biology)offers a different understanding of the role of genetic change in evolution.Which of the following statements best summarizes this understanding?

A)Genetic mutations are not as important in evolutionary change as the environment in which the organism develops.
B)Changes in cell-cell interactions in a parent's body can lead to phenotypic change in offspring.
C)Similar genes are found in most developing animal bodies;changes in the times and places they are expressed can lead to phenotypic variation.
D)Greater numbers of genes,rather than the ways in which they are regulated,lead to the development of more complex animals over time.

Question 30

What types of changes in the regulation of development can lead to evolutionarily significant morphological changes?

A)Changes in when developmental genes are expressed.
B)Changes in where developmental genes are expressed.
C)Changes in development are not evolutionarily significant.
D)Both A and B are evolutionarily significant.

Question 31

The plant Veratrum californicum contains an alkaloid that can severely affect normal developmental processes.When pregnant ewes eat this plant,their lambs may suffer deformities such as cyclopia (the development of a single central eye)and limb abnormalities.Experiments have shown that in the presence of this alkaloid,a protein known as Sonic hedgehog does not diffuse into limb buds of the embryo.The alkaloid inhibits cholesterol synthesis.What do you think is the explanation for the alkaloid's effect on development?

A)The alkaloid blocks the transcription of Sonic hedgehog.
B)The alkaloid cleaves Sonic hedgehog,making it ineffective.
C)Cholesterol is needed for the diffusion of Sonic hedgehog into the limb bud.
D)Cholesterol is needed for the translation of Sonic hedgehog mRNA.

Question 32

Undifferentiated cells that continue to proliferate throughout an individual's life are referred to by what terms in plants and animals respectively?

A)stem cells and stem cells
B)meristems and meristems
C)stem cells and meristems
D)meristems and stem cells

Question 33

In snake populations,rare individuals are found that have well-developed hind limbs.They are normal in all other respects.This finding shows that

A)some snakes have mutations in Hox genes that permit development of limbs.
B)snakes retain the genes for hindlimb pattern formation,even though the genes are usually not activated during development.
C)some snakes may lack the regulatory inhibitors necessary for normal limbless development.
D)all of the above might explain this rare condition.

Question 34

For which of the following reasons are adult stem cells said to be multipotent?

A)They can divide and develop into any part of the multicellular organism.
B)They can only divide and develop into a limited number of related cells types.
C)They can divide and develop to form a complete multicellular organism.

Question 35

Many different lineages of animals share similar pattern-formation gene complexes.The study of how these shared complexes function in evolution is termed

A)convergent evolution.
B)conservative evolution.
C)regulatory evolution.
D)evo-devo (evolutionary developmental biology).

Question 36

Individual organisms often get larger throughout their lifetime (up until a certain point).Which of the processes below plays a role in this gain in size?

A)meiosis
B)mitosis
C)fertilization
D)budding

Question 37

Scientists have found that the lifetimes of mRNAs coding for pair-rule regulatory elements in Drosophila embryos may be measured in minutes.What does this suggest about the overall developmental plan of an animal body?

A)mRNAs in general have short lifetimes;this is not a surprising finding.
B)Each segment specified by pair-rule mRNAs is completely determined in the embryo in a very short time.
C)Building an animal body requires a sequence of steps;each of these steps is precisely timed.
D)Timing of pair-rule sequence determination is not as important as spatial signaling.

Question 38

Cells in a developing embryo are subject to a number of regulatory pressures.Which of the following is NOT a source of regulatory signals in animal development?

A)oocyte cytoplasm
B)sperm nucleus
C)nearby cells
D)extracellular matrix

Question 39

Which of the following terms refers to a cell that is capable of dividing and developing into a limited number of cell types in a multicellular organism?

A)multipotent
B)pluripotent
C)totipotent