Question 1

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?

Accepted Answer

The fact that similar numbers of genes were transcribed at a particular time in development among species with different genome sizes suggests that the number of genes transcribed is tightly regulated and independent of genome size. This means that nuclear DNA complexity is not necessarily related to the complexity of mRNAs transcribed during development. It does not necessarily mean that some species retain unused DNA or that genome size has nothing to do with physical complexity.

Question 2

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

Accepted Answer

Both changes in when developmental genes are expressed and where they are expressed can lead to significant morphological changes during evolution. Alterations in the timing of gene expression can result in changes in the duration and rate of development, potentially leading to new or modified morphological features. Changes in spatial expression patterns can result in the emergence of new developmental pathways or alterations to existing ones, also leading to significant morphological changes. Both of these types of developmental changes have been observed and studied in numerous examples of evolutionary change.

Question 3

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

Accepted Answer

The study of how shared pattern-formation gene complexes function in evolution is a key aspect of evolutionary developmental biology, also known as evo-devo. This field focuses on how changes in developmental processes contribute to the evolution of new traits and forms in organisms. The other answer choices do not accurately describe this specific area of study.

Question 4

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?

Accepted Answer

The ventral axis runs towards the organism's belly, while the dorsal axis runs towards its back. The posterior axis runs towards the organism's tail, and the anterior axis runs towards its head.

Question 5

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

Accepted Answer

Embryonic stem cells are not terminally differentiated, meaning they have not yet become specialized cells like muscle or nerve cells. They have the potential to become any type of cell in the body, making them valuable for medical research and potential therapies.

Question 6

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

Accepted Answer

Dolly the sheep was cloned by using a differentiated somatic cell from a Finn Dorset sheep, which was fused with an enucleated egg cell from a Scottish Blackface sheep, effectively making her genetically identical to the somatic cell donor, not the egg-cell donor. This process demonstrated that a differentiated cell could reprogram to an embryonic state and develop into a new organism.

Question 7

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

Accepted Answer

Lou Gehrig's disease, also known as ALS, is a neurodegenerative disease that results in the death of motor neurons and muscle weakness, but it is not an example of the normal process of apoptosis during organ and tissue development. The other options listed (B, C, and D) are all examples of apoptosis occurring naturally during development or growth of organisms.

Question 8

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?

Accepted Answer

The answer of During development, what a cell differentiates into...

Question 9

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

Accepted Answer

Duplication of Hox genes allowed for the evolution of novel forms because it provided extra genetic material that could be modified and mutated without disrupting the original functioning of the gene. This allowed for the development of new structures and body plans that contributed to the diversification of animal life.

Question 10

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?

Accepted Answer

The sperm nucleus does not provide regulatory signals in animal development. It only contributes genetic information to the zygote. Nearby cells, the extracellular matrix, and the oocyte cytoplasm all provide important regulatory signals in animal development.

Question 11

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

Accepted Answer

In plants, undifferentiated cells that continue to proliferate throughout an individual's life are referred to as meristems. In animals, they are referred to as stem cells. Therefore, option B, meristems and stem cells, is the correct choice.

Question 12

Cellular differentiation results from

Accepted Answer

Cellular differentiation results from differential gene expression, meaning that different genes are activated or expressed in different cells, leading to different functions and characteristics. This gene expression is regulated by various mechanisms such as the binding of regulatory proteins and epigenetic modifications, without changes in the actual genetic makeup or DNA sequence of the cells. Mutations in DNA can also lead to changes in gene expression, but they are not the primary mechanism for cellular differentiation.

Question 13

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?

Accepted Answer

The short lifetimes of mRNAs coding for pair-rule regulatory elements suggests that the developmental plan of an animal body requires a sequence of steps that are precisely timed. This is necessary for the proper initiation and patterning of each segment in a very short period of time. The timing of pair-rule sequence determination and spatial signaling are both important factors in this process. The general finding that mRNAs have short lifetimes is not particularly relevant to the question.

Question 14

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?

Accepted Answer

The Bicoid gene product is a morphogen that specifies anterior structures in Drosophila embryos. Injecting it into the posterior end would lead to the formation of anterior structures at both ends of the embryo.

Question 15

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

Accepted Answer

All human cells contain the same set of genes, including the gene for alcohol dehydrogenase. The difference in cell function is due to which genes are expressed, not which genes are present.

Question 16

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

Accepted Answer

Adult stem cells are said to be multipotent because they can only divide and develop into a limited number of related cell types. This means that their potential to differentiate is restricted compared to pluripotent stem cells, which can develop into any type of cell in the body.

Question 17

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?

Accepted Answer

A multipotent cell can divide and differentiate into a limited number of cell types in a multicellular organism. Pluripotent cells can differentiate into almost any cell type, and totipotent cells can differentiate into any cell type plus extraembryonic cells.

Question 18

What does the term "genetic equivalence" refer to?

Accepted Answer

Genetic equivalence refers to the fact that all cells in an organism contain the same genetic information. While cells differentiate and specialize in their functions, they do not lose any genes. Therefore, differentiated cells of a plant contain the same genes as other cells in the same plant.

Question 19

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?

Accepted Answer

Evo-devo emphasizes the role of changes in gene expression, rather than mutations in the actual genetic sequence, as the major source of phenotypic variation and evolutionary change. This is because most developing animal bodies share a core set of genes, but the timing and location of their expression can vary greatly, leading to diverse morphologies.

Quiz 21: Gene Structure and Development