Question 1

Suppose there was a mutation in the segment- polarity genes of Drosophila. What do you suppose might be the outcome?
A) Antennae will appear in a different part of their usual segment.
B) Legs will appear in the place of antennae.
C) Every other segment of the embryo will be missing.
D) Several segments of the embryo will be missing.

Accepted Answer

A

Question 2

The protein of the bicoid gene in Drosophila determines
A) the medial- lateral axis of the embryo.
B) the anterior- posterior axis of the embryo.
C) the number of segments in the embryo.
D) the ventral- lateral axis of the embryo.

Accepted Answer

The protein of the bicoid gene in Drosophila determines the anterior-posterior axis of the embryo, providing positional information that leads to the development of specific structures in the head and thorax.

Question 3

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

Accepted Answer

Cloning of plants from cuttings involves taking a piece of a mature plant and rooting it to grow a new, genetically identical plant. This demonstrates that genetic information is retained in mature plant cells and can be used to regenerate a whole new organism. This process does not involve embryonic mRNAs or reversing the differentiation process.

Question 4

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

Accepted Answer

The Bicoid protein, being expressed while the Drosophila embryo is still in a syncytial state (where cell divisions are not fully developed), allows for its diffusion throughout the embryo to form a concentration gradient. This gradient is crucial for anterior-posterior axis development, as discovered by Nüsslein-Volhard and Wieschaus.

Question 5

Suppose the pair- rule genes were inactivated in Drosophila embryos. What is the likely result of the experiment?
A) The embryos would have missing alternate segments.
B) The embryos would develop normally.
C) The embryos would have impaired anterior- posterior polarity.
D) The embryos would lack several segments.

Accepted Answer

Pair-rule genes in Drosophila are responsible for defining alternate segments during embryonic development. If these genes were inactivated, the embryos would indeed have missing alternate segments, leading to a segmented body plan that is incomplete.

Question 6

Gastrulation is an important event in early embryonic development. Which of the following is NOT a result of this process?
A) determination of cell types as a result of cell-cell interactions
B) movement and alignment of many embryonic cells
C) formation of three embryonic cell layers
D) formation of specialized plant tissues

Accepted Answer

Gastrulation is a process that occurs during the early stages of embryonic development in animals, and is responsible for the formation of the three germ layers (endoderm, mesoderm and ectoderm). This process involves the movement and alignment of many embryonic cells, and the determination of cell types as a result of cell-cell interactions. However, it is not involved in the formation of specialized plant tissues, which is a process that occurs only in plants, and not in animals.

Question 7

Cellular differentiation is usually produced by
A) morphogenesis.
B) differences in DNA sequences.
C) differences in gene expression.
D) differences in gene copy numbers.

Accepted Answer

Cellular differentiation is the process by which cells become specialized in structure and function. This differentiation is controlled by the expression of specific genes. As cells differentiate, certain genes become more or less active, leading to differences in the proteins that are produced and ultimately to differences in cellular structure and function. Therefore, differences in gene expression are the main reason for cellular differentiation.

Question 8

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

Accepted Answer

The answer of When is a cell considered differentiated?
A) when...

Question 9

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) destroying embryonic nerve cells as part of "wiring" an effective nervous system
C) elimination of dangerous immune cells
D) sculpting of digits in the developing hindlimb

Accepted Answer

Apoptosis plays a major role in the growth of nerves and blood vessels into a body segment, as well as in destroying embryonic nerve cells and eliminating dangerous immune cells. However, it likely would not play a major role in sculpting of digits in the developing hindlimb, as other processes such as cell differentiation and proliferation are more important for this developmental process.

Question 10

Which of the following would constitute evidence that differentiated cells retain all the genes of developing cells?
A) Differentiated cells lose their polarity if removed from the organism.
B) Developing cells have many mRNA transcripts that can hybridize with DNA from mature cells.
C) Nuclei from mature cells can direct the development of an entire individual.
D) Differentiated cells generally synthesize a specific group of proteins.

Accepted Answer

The fact that nuclei from mature, differentiated cells can direct the development of an entire individual provides strong evidence that the differentiated cells retain all the genes of developing cells. This is demonstrated by experiments where nuclei from differentiated cells are transplanted into an enucleated egg, and the resulting organism develops normally. This shows that the differentiated nucleus contains all the genetic information needed to generate an entire organism, indicating that the differentiated cells must retain all the genes of developing cells. Choice A is incorrect because the loss of polarity is not necessarily related to gene retention. Choice B is incorrect because the hybridization of mRNA with DNA does not necessarily demonstrate that all genes are retained. Choice D is incorrect because the synthesis of specific groups of proteins is related to the differentiation of cells and does not necessarily indicate that all genes are retained.

Question 11

Muscle cells differ from nerve cells mainly because they
A) use different genetic codes.
B) express different genes.
C) have unique ribosomes.
D) contain different genes.
E) have different chromosomes.

Accepted Answer

Muscle cells and nerve cells have different functions and therefore express different genes to carry out these functions. While they may have some differences in their genetic code, ribosomes, and chromosomes, these differences are not the main reason for their functional differences.

Question 12

Suppose you found several Drosophila mutants that possessed additional legs growing out of the head segments. The probable mutation would be found in
A) homeotic genes.
B) gap genes.
C) pair- rule genes.
D) segment- polarity genes.

Accepted Answer

Homeotic genes determine the identity of each segment in an organism's body plan, and therefore mutations in these genes can lead to abnormal development of body structures. In the case of Drosophila mutants that possess additional legs growing out of the head segments, a mutation in homeotic genes is the most likely explanation. The formation of additional legs suggests a transformation of head segments into thoracic segments, where legs are normally found.

Question 13

In combination, what do the products of gap genes, pair- rule genes, and segmentation polarity genes of fruit flies do?
A) They direct cell movements during differentiation.
B) They trigger the reorganization of the larval body into an adult body.
C) They define the segmented body plan of the embryo.
D) They set up the back- to- belly axis of the larval body.

Accepted Answer

The products of gap genes, pair-rule genes, and segmentation polarity genes work together to define the segmented body plan of the fruit fly embryo. Gap genes create broad regions along the anterior-posterior axis, pair-rule genes divide those into segments, and segmentation polarity genes further refine the segmentation and establish polarity within each segment. They do not direct cell movements during differentiation, trigger the reorganization of the larval body into an adult body, or set up the back-to-belly axis of the larval body.

Question 14

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

Accepted Answer

Bicoid is a protein that functions as a morphogen in Drosophila (fruit flies), crucial for the early determination of the embryo's anterior region. If bicoid were present in high concentrations throughout the embryo, it would interfere with the normal gradient necessary for specifying posterior regions, potentially leading to embryos lacking proper development of those posterior regions.

Question 15

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

Accepted Answer

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

Question 16

What was the experimental focus of the preliminary genetic screening performed by Nüsslein- Volhard and Wieschaus?
A) to discover the bicoid gene
B) to generate two- tailed fruit- fly embryos
C) to identify fruit flies with mutations in genes that control fruit- fly development
D) to evaluate the mutagenic properties of varied treatments

Accepted Answer

The preliminary genetic screening performed by Nüsslein-Volhard and Wieschaus aimed to identify fruit flies with mutations in genes that control fruit-fly development. They wanted to find genes that are important for proper embryonic development and used mutagens to induce random mutations in the flies. This allowed them to study the effects of specific genes on development.

Question 17

What is common to gap genes, segment- polarity genes, and homeotic genes?
A) They are unique to Drosophila embryos.
B) They act independently of one another.
C) They can be activated at any time during development.
D) They code for transcription regulatory factors.

Accepted Answer

All three types of genes (gap genes, segment-polarity genes, and homeotic genes) code for transcription regulatory factors. Gap genes and segment-polarity genes are involved in establishing the initial segmentation pattern in the embryo, while homeotic genes determine the identity of each segment and the structures that develop from them. This is true not only in Drosophila, but also in other organisms that undergo similar processes of segmentation and body patterning during development.

Question 18

Communication within and between cells of an embryo can include all of the following EXCEPT
A) increased concentration of signaling molecules.
B) changes in gene transcription.
C) changes in gene sequences.
D) changes in binding to regulatory sequences.

Accepted Answer

Changes in gene sequences do not occur during communication within and between cells of an embryo. Rather, communication involves changes in the concentration of signaling molecules, changes in gene transcription, and changes in binding to regulatory sequences.

Question 19

During Drosophila development, there is a regulatory cascade of gene activation. The proper sequence for this cascade is
A) bicoid, pair- rule genes, gap genes, and segment polarity genes.
B) bicoid, segment- polarity genes, gap genes, and pair- rule genes.
C) bicoid, gap genes, segment polarity genes, and pair- rule genes.
D) bicoid, gap genes, pair- rule genes, and segment polarity genes.

Accepted Answer

The correct sequence in Drosophila development starts with maternal effect genes like bicoid, followed by gap genes that define broad areas, then pair-rule genes that refine the pattern into segments, and finally segment polarity genes that detail the anterior-posterior axis within each segment.

Question 20

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

Accepted Answer

In plants, many cell types have the ability to dedifferentiate and re-differentiate into other cell types, allowing for more plasticity in development. Animal cell types, once determined, generally cannot change their differentiated characteristics.

Quiz 21: Gene Structure and Development

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

The protein of the bicoid gene in Drosophila determines

Cloning of plants from cuttings demonstrates that

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?

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

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

Cellular differentiation is usually produced by

When is a cell considered differentiated?

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

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

Muscle cells differ from nerve cells mainly because they

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

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

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?

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?

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

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

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

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

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?