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.

Accepted Answer

In the immune system, DNA sequences can rearrange to create diverse antibodies, making these cells genetically different from their embryonic counterparts.

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

Accepted Answer

Changes in gene sequences cannot occur during embryonic development because the genetic material is already determined and passed down from the parents. The other options are all examples of communication within and between cells of an embryo.

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

Accepted Answer

The bicoid gene in Drosophila plays a crucial role in determining the anterior-posterior axis of the embryo. The protein encoded by the bicoid gene is localized at the anterior end of the developing egg cell and establishes this axis by activating the transcription of target genes in a concentration-dependent manner. The bicoid protein gradient is essential for the proper development of the head and thorax of the fly, as well as for the placement of the germ cells. Therefore, the correct answer is A) anterior-posterior axis.

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

Accepted Answer

A cell is considered differentiated when it manufactures proteins specific to a particular cell type, indicating it has acquired specialized functions.

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.

Accepted Answer

Evo-devo emphasizes that changes in the expression of similar genes found in most developing animal bodies can lead to phenotypic variation. These changes can be brought on by alterations to the timing and location of when these genes are expressed, rather than by changes in the genetic code itself.

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.

Accepted Answer

Gap genes, segment-polarity genes, and homeotic genes all code for transcription regulatory factors that control gene expression during development in Drosophila embryos. These genes are critical for establishing the body plan and segmentation of the embryo.

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.

Accepted Answer

The segment-polarity genes control the positioning of structures within each segment of the Drosophila embryo. A mutation in these genes could result in the development of structures in the wrong place within their respective segments. Therefore, the appearance of antennae in a different part of their usual segment is the most likely outcome.

Question 8

The predominant mechanism driving cellular differentiation is the difference in gene _____.
A)expression
B)sequences
C)order
D)replication

Accepted Answer

Cellular differentiation involves the activation or suppression of specific genes within a cell's genome, resulting in a unique pattern of gene expression that distinguishes it from other cell types. While differences in gene sequences may contribute to cellular differentiation, it is primarily gene expression that dictates a cell's identity and function. Gene order and replication are not directly related to cellular differentiation.

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

Accepted Answer

The correct sequence for gene activation during Drosophila development starts with the maternal effect gene bicoid, followed by the activation of gap genes, then pair-rule genes, and finally segment-polarity genes. This sequence is crucial for the proper segmentation and development of the embryo.

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

Accepted Answer

Growth of nerves and blood vessels actually involves branching and pruning, not apoptosis. Apoptosis is involved in the other three options listed.

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.

Accepted Answer

While all other options are characteristics shared by both plant and animal development, the ability for cell types to change their differentiated characteristics is unique to plant development due to the presence of totipotent cells, which can differentiate into any cell type. In animal development, cells typically lose the ability to differentiate into any cell type once they have taken on a specific differentiated state.

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

Accepted Answer

Homeotic genes control the development of body structures and determine segment identity. Mutations in these genes can lead to abnormal or extra body parts in insects, including additional legs growing out of the head segment in Drosophila mutants.

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.

Accepted Answer

The answer of Suppose the pair-rule genes were inactivated in...

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.

Accepted Answer

The observation by Nüsslein-Volhard and Wieschaus was the presence of a concentration gradient of the Bicoid protein in the syncytial embryo. The fact that the embryo is still syncytial indicates that the divisions between cells are not yet fully developed, and the presence of a concentration gradient suggests that the Bicoid protein is diffusing throughout the embryo. Therefore, choice B is the best answer.

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.

Accepted Answer

The observation that nuclei from mature (differentiated) cells can direct the development of an entire organism provides evidence that differentiated cells retain all the genes of developing cells. This is because for an entire organism to develop from the nucleus of a single differentiated cell, that cell must have contained all of the genetic information needed for the organism's development. Options A and B do not provide evidence that differentiated cells retain all the genes of developing cells, and option D is not relevant to the question.

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.

Accepted Answer

The products of gap genes, pair-rule genes, and segmentation polarity genes work together to define the segmented body plan of the Drosophila embryo. Gap genes establish broad regions of the embryo, pair-rule genes divide these regions into alternating segments, and segmentation polarity genes determine segment polarity and organize segments in the anterior-posterior axis. This process sets up the basic body plan of the developing fruit fly embryo.

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

Accepted Answer

Hox genes produce transcription factors that regulate the expression of downstream genes involved in developmental processes.

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

Accepted Answer

The purpose of the preliminary genetic screening was to identify fruit flies with mutations in genes that control fruit-fly development. By exposing adult fruit flies to mutagenic treatments, Nüsslein-Volhard and Wieschaus were able to generate offspring with random mutations. By analyzing the resulting embryos, they were able to identify fruit flies with mutations in genes involved in developmental processes.

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

Accepted Answer

The answer of Cloning of plants from cuttings demonstrates that...

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.

Accepted Answer

Bicoid is a protein that functions as a morphogen in Drosophila (fruit flies), crucial for the early development of embryos. It is normally concentrated at the anterior end of the embryo and establishes the anterior-posterior axis by activating the transcription of genes required for the development of anterior structures. If bicoid were present in high concentrations throughout the embryo, it would interfere with the normal gradient required for specifying the posterior regions, potentially leading to embryos that lack proper development of those posterior regions.

Quiz 21: Principles of Development

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?

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

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

When is a cell considered differentiated?

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

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

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

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

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

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

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

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

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?

Which observation below provides evidence that differentiated cells retain all the genes of developing cells?

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

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?

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?

Cloning of plants from cuttings demonstrates that _____.

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?