Deck 21: Gene Structure and Development

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.

Answer 1

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.

Answer 2

B

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.

Answer 3

B

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.

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.

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

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.

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

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

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.

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.

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.

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.

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.

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

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

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.

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.

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.

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.

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) Nuclear DNA complexity is unrelated to the complexity of mRNAs transcribed during development.
D) Genome size has nothing to do with the physical complexity of the species.

Question 22

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

Question 24

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) ventral
B) dorsal
C) posterior
D) anterior

Question 25

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

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

Question 26

Which of the following is true of the cloning experiment that resulted in Dolly the sheep?

A) Dolly was genetically identical to the egg- cell donor.
B) Dolly was cloned by fusing the nuclei from two separate eggs harvested from the same individual.
C) Dolly was cloned by fusing an egg with an embryonic stem cell.
D) Dolly was infertile, which indicated incomplete nuclear reprogramming.
E) Dolly was cloned by using a differentiated cell fused to an egg from another breed of sheep.

Question 27

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

A) Lou Gehrig's disease
B) leaves falling off trees in the fall
C) petals falling off flowers after pollination
D) death of cells between the toes in chicken embryos

Question 28

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) ventral
B) dorsal
C) anterior
D) posterior

Question 29

The duplication of homeotic Hox) genes has been significant in the evolution of animals because it

A) reduced morphological diversity into simpler forms of life.
B) caused the extinction of major groups.
C) allowed animals to survive on significantly fewer calories.
D) permitted the evolution of novel forms.

Question 30

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

Question 31

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 stem cells
C) meristems and meristems
D) stem cells and meristems

Question 32

Cellular differentiation results from

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

Question 33

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) Timing of pair- rule sequence determination is not as important as spatial signaling.
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) mRNAs in general have short lifetimes; this is not a surprising finding.

Question 34

The Bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?

A) Anterior structures would form in both ends of the embryo.
B) The embryo would probably show no anterior development and die.
C) The embryo would grow extra wings and legs.
D) The embryo would develop normally.
E) The embryo would grow to an unusually large size.

Question 35

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 36

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

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

Question 37

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) pluripotent
B) totipotent
C) multipotent

Question 38

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) During development, sending and receiving of signals via cell- cell interactions makes the cells involved more equal.
D) Differentiated animal cells can share gene products with each other, resulting in a balance of products among the cells.

Question 39

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