General Biology

Cytoplasmic determinants __________.

Cells can influence each other's development by a process known as __________.

Instead of developing a head and a tail, an abnormal Drosophila embryo develops two tails. This is most likely due to __________.

Cell differentiation is first observable when __________.

During the process of differentiation, cells __________.

__________ can give rise to any type of cell whereas __________ can give rise to a subset of cell types.

The similarity of the homeobox in many different kinds of organisms is evidence __________.

The highly conserved sequence element present within homeotic genes is called the __________.

What are the two main genetic and cellular mechanisms that underlie differentiation?

Which of the following statements is true?

Which of the following statements is true?

The products of Hox genes __________.

Scientists have recently developed a process by which a skin cell from a human can be triggered to develop into a human heart muscle cell. This is possible because                   . a. most cells in the human body contain the genetic instructions for making all types of human cells; b. a skin cell is produced when all genes in the cell are expressed; turning off some genes in the cell results in a heart cell; c. scientists can add new genes to old cells to make them take different forms; d. a skin cell expresses only recessive alleles, so it can be triggered to produce dominant heart cell alleles; e. it is easy to mutate the genes in skin cells to produce the alleles required for other cell types

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of a. the influence of environment on development. b. paedomorphosis. c. a change in a developmental gene or in its regulation that altered the spatial organization of body parts. d. heterochrony.

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene a. normally leads to formation of head structures. b. normally leads to formation of tail structures. c. is transcribed in the early embryo. d. is a protein present in all head structures.

Cell differentiation always involves a. transcription of the myoD gene. b. the movement of cells. c. the production of tissue-specific proteins. d. the selective loss of certain genes from the genome.

What is the connection between genetic regulatory cascades and the observation that differentiation is a step-by-step process?

A friend is interested in isolating genes that are expressed solely in liver cells but only has access to skin cells. She asks you for advice on whether to start her studies. What will you say?

Which of the following provides the strongest evidence for the conservation of tool-kit genes? a. Bicoid moved from one fly embryo into the posterior of another fly embryo causes the formation of two head regions. b. Mutation of an unrelated gene in another species of fly has a similar effect to mutation of bicoid in Drosophila. c. A mouse Hox gene can be used to take over the function of a mutated Drosophila Hox gene. d. Sheep can be cloned by fusing a differentiated adult cell with an enucleated egg.

The following predictions ask you to consider how genetic regulatory cascades provide positional information. Select True or False for each statement. T/F Mutation of a gene at one level of a regulatory cascade will affect the expression of genes at all levels of the cascade. T/F Mutation of a gene that is expressed later in a regulatory cascade will affect a smaller region of the body than mutation of gene that is expressed early in the cascade. T/F In the regulatory cascade used by Drosophila, a gene at one level of the cascade will be controlled only by genes at the level immediately above it. T/F Genes that control the largest regions of the Drosophila embryo are not transcribed in the embryo.

Some stickleback fish develop protective spines, and other stickleback fish are spineless. Spine development is controlled by the expression of a gene known as Pitx1. The spineless phenotype is due to a mutation in Pitx1 that results in no expression of Pitx1 during development in regions where spines would otherwise form. When scientists compared the Pitx1 coding sequence in spined and spineless fish, they found this sequence was the same in both types of fish. Propose plausible hypotheses for the location of this mutation and for how it alters spine development.

Imagine a situation in which a morphogen has its source at the posterior end of a Drosophila embryo. Every 100 µm from the posterior pole, the morphogen concentration decreases by half. If a cell required 1/16th the amount of morphogen found at the posterior pole to form part of a leg, how far from the posterior pole would the leg form? a. 100 μm b. 160 μm c. 400 μm d. 1600 μm

What is apoptosis? a. an experimental technique used to kill specific cells b. programmed cell death that is required for normal development c. a pathological condition observed only in damaged or diseased organisms d. a developmental mechanism unique to the roundworm C. elegans

Type I diabetes is a form of diabetes that is due to the loss of insulin-producing cells of the pancreas. The potential of stem cells—in particular, induced pluripotent stem (iPS) cells—for therapy has gotten a lot of press. If researchers were attempting to stimulate the differentiation of iPS cells, which of the following would they most likely add to the cell-culture medium (the liquid surrounding the cells)? a. activin A, an extracellular signal protein b. Sox-2, a transcription factor active in early development c. Grb-2, an intracellular signal transduction protein d. lactase, an enzyme that catalyzes the breakdown of lactose

Type I diabetes is a form of diabetes that is due to the loss of insulin-producing cells of the pancreas. The potential of stem cells—in particular, induced pluripotent stem (iPS) cells—for therapy has gotten a lot of press. What are iPS cells? a. cells taken from early human embryos b. cells taken from the pancreas of people without diabetes c. cells derived by de-differentiating specialized adult cells d. cells derived by differentiating pancreas precursor cells

In adult animals,            are a source of undifferentiated cells that can divide to produce cells that can specialize.

The development of a zygote into a blastula is called __________.

Which stage of development is common in amphibians but not seen in mammals?

Which of the following describes the correct sequence of stages during embryogenesis?

A sea urchin sperm penetrates the jelly coat of an egg and adheres to receptor proteins on the egg's surface as a result of __________.

How does a zygote differ from an ovum?

After a sperm penetrates an egg, a fertilization envelope forms. This envelope __________.

The period of repeated cell divisions without significant cell growth results in formation of the blastula and is called __________.

During cleavage the single large zygote is converted into a __________.

How is the animal hemisphere of a frog blastula different from the vegetal hemisphere?

What is the most likely trigger of egg activation?

Which of the following is true of meroblastic cleavage?

As an animal develops, organs form and the body transforms into a shape typical of the species in a process called __________.

People with Kartagener's syndrome suffer from a variety of ailments, including the intriguing condition known as situs inversus, a reversal of the abdominal and thoracic organs. This condition occurs because of __________.

The digits of a developing vertebrate limb respond to molecules that establish an anterior-posterior axis. These molecules originate in __________.

In an experiment on eye development, a thin piece of aluminum foil was placed between the bulging wall of the brain and the overlying ectoderm where the eye normally forms. Wherever the foil was placed, the lens failed to develop because the foil __________.

Up to the eight-cell stage, the blastomeres of a mouse embryo can each form a complete embryo if isolated. This indicates that __________.

What primitive feature forms during gastrulation?

The primitive streak of a bird embryo is the functional equivalent of the __________ in a frog.

What is the embryonic origin of the lining of the digestive tube?

One difference between the blastula and gastrula stages of development is that __________.

Which of the following events occurs only during organogenesis?

In humans, the skeleton and muscles develop from the embryonic __________.

The human brain develops from __________.

Which of the following extraembryonic membranes functions in gas exchange and encloses a chamber for the deposition of wastes of a bird embryo?

In mammals, the __________ facilitates implantation in the uterine wall.

Evidence suggests that folic acid may help prevent the development of spina bifida, a common disabling birth defect. It is recommended that women increase their folic acid intake during pregnancy, especially in the first three months. Why is the timing of the folic acid intake relevant?

If you wanted to examine the extraembryonic membranes surrounding a lizard or mouse embryo, you would first have to cut through which of the following to see all the others?

During the development of most animals, cleavage leads to __________.

Which of the following correctly lists the embryonic stages in the order that they develop?

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were a. totipotent. b. determined. c. differentiated. d. mesenchymal.

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water? a. extraembryonic membranes b. yolk c. cleavage d. gastrulation

The archenteron develops into a. the mesoderm. b. the endoderm. c. the placenta. d. the lumen of the digestive tract.

If an egg cell were treated with EDTA, a chemical that binds calcium and magnesium ions, a. the acrosomal reaction would be blocked. b. the fusion of sperm and egg nuclei would be blocked. c. the fast block to polyspermy would not occur. d. the fertilization envelope would not form.

The cortical reaction of sea urchin eggs functions directly in a. the formation of a fertilization envelope. b. the production of a fast block to polyspermy. c. the generation of an electrical impulse by the egg. d. the fusion of egg and sperm nuclei.

In humans, identical twins are possible because a. extraembryonic cells interact with the zygote nucleus. b. convergent extension occurs. c. early blastomeres can form a complete embryo if isolated. d. the gray crescent divides the dorsal-ventral axis into new cells.

Which of the following is common to the development of both birds and mammals? a. holoblastic cleavage b. epiblast and hypoblast c. trophoblast d. gray crescent

A region of dividing cells in a plant is called a __________.

During normal development, Acacia koa plants first produce compound juvenile leaves and later produce adult sickle-shaped leaves. Which of the following statements is correct?

The homeotic gene GLABRA-2 controls cellular differentiation in the root epidermis of Arabidopsis. Which of the following statements is/are correct?

In a young cell just produced by mitosis, the cellulose microfibrils are arranged in horizontal rings. Which of the following accurately explains how the cell will grow longer?

Which example below is the site of primary growth that results in the plant’s increasing in height?