Deck 21: Principles of Development

Question 1

Modern cloning techniques have demonstrated that the vast majority of differentiated cells are genetically equivalent to developing cells in the embryo.What example below 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.

Answer 1

B

Question 2

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

Answer 2

D

Question 3

The protein of the bicoid gene in Drosophila determines the _____ of the embryo.

A)anterior-posterior axis
B)anterior-lateral axis
C)posterior-dorsal axis
D)posterior-ventral axis

Answer 3

A

Question 4

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 5

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 in an animal's genome produce a wider variety of morphological structures and patterns.

Question 6

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.

Question 7

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 8

The predominant mechanism driving cellular differentiation is the difference in gene _____.

A)expression
B)sequences
C)order
D)replication

Question 9

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 10

Programmed cell death,apoptosis,plays a major role in all of the following developmental situations except:
_____.

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

All of the following characteristics are shared between plant and animal development except:

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.

Question 12

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

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

Question 13

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 14

When the Bicoid protein is expressed in Drosophila,the embryo is still syncytial (divisions between cells are not yet fully developed).This information 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 15

Which observation below provides 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)Not all mature cells are capable of differentiation.

Question 16

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 17

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 is 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 18

What was the experimental purpose of the preliminary genetic screening performed in which Nüsslein-Volhard and Wieschaus exposed adult fruit flies to treatments that would cause mutations in their offspring?

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 19

Cloning of plants from cuttings demonstrates that _____.

A)an individual plant cell cannot de-differentiate and then redifferentiate
B)differentiated plant cells may contain embryonic mRNAs
C)plants can reverse the differentiation process
D)mature plant cells retain genetic information

Question 20

Suppose the protein specified by bicoid was 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 21

In snake populations,rare individuals are found that have well-developed hind limbs,but are normal in all other respects.These unusual snakes suggest 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)mutations in genes that repress expression of hindlimb organizer genes can cause a snake to have limbs
D)All of the above might explain this rare condition.

Question 22

Animal species exhibit an enormous diversity of genetic information contained in nuclear DNA.This difference in DNA may be reflected in very different genome sizes.Scientists investigating the possibility that animals with more complex morphological structures might express greater numbers of different types of mRNAs during development found that similar numbers of genes were transcribed at a particular time in development in species whose genome sizes 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,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 23

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 24

All of the following are true of embryonic stem cells except _____.

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

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.