Deck 14: Genes, Development, and Evolution

Question 1

The process by which the developmental fate of a cell is established is called

A) determination.
B) morphogenesis.
C) differentiation.
D) induction.
E) totipotency.

Answer 1

A

Question 2

You are working with salamander embryos in the early gastrula stage and transplant cells destined to become neural tissue to a region that would normally form epidermis.As the embryo develops further,you find that the transplanted cells form epidermis instead of neural tissue.You repeat the experiment on a late-stage gastrula and find that as the embryo develops further,the transplanted cells form neural tissue.From these results,you can conclude that the cells being transplanted

A) were differentiated prior to the time they were transplanted in each experiment.
B) were determined to form neural tissue prior to the early gastrula stage.
C) underwent morphogenesis between the early and late gastrula stages.
D) became determined to become neural tissue between the early and late gastrula stages.
E) differentiated into neural tissue between the early and late gastrula stages.

Answer 2

D

Question 3

Which series represents the correct chronological order of the developmental stages in animals such as the sea urchin?

A) Embryo,larva,zygote
B) Embryo,zygote,larva
C) Zygote,larva,embryo
D) Zygote,embryo,larva
E) Larva,embryo,zygote

Answer 3

D

Question 4

Before a differentiated plant cell can become totipotent,it must

A) be induced to dedifferentiate.
B) undergo morphogenesis.
C) be transplanted into a gastrula.
D) form a root.
E) be transplanted to the soil.

Question 5

Which stage in plant development most closely resembles the blastula stage in animal development?

A) Eight-celled embryo
B) Globular embryo
C) Heart embryo
D) Torpedo embryo
E) Gastrula

Question 6

Which statement about the processes of development is true?

A) Morphogenesis occurs prior to gastrulation.
B) Determination occurs prior to differentiation.
C) Morphogenesis does not occur before the adult stage.
D) Morphogenesis occurs prior to determination.
E) Differentiation occurs prior to determination.

Question 7

If a cell that has been isolated from the root of a carrot is given the appropriate nutrients and cues,it will give rise to a mass of undifferentiated cells,which can go on to develop into a

A) clone of the original carrot.
B) different species of carrot.
C) carrot that is genetically distinct from the original.
D) carrot embryo called a callus.
E) root of a carrot that is genetically distinct from the original.

Question 8

Which statement about developmental processes is true?

A) Biologists usually can observe determination in cells through microscopic studies.
B) Differentiation of cells cannot occur unless morphogenesis has first occurred.
C) Differentiation consists of the actual biochemical,structural,and functional changes of a cell.
D) In an embryo,determination begins after the larval stage.
E) Differentiation occurs in animal embryos but not in plant embryos.

Question 9

Which technique or study would be most useful in testing the hypothesis that "the fate of the cells in an early fish embryo is irrevocably determined"?

A) Transplanting cells from one region to another
B) Monitoring gene expression in the cells and looking for differences in different regions
C) Examining structural differences among cells in different regions by means of a light microscope
D) Using nuclear transfer procedures
E) Observing whether the cells are undergoing apoptosis

Question 10

Which of the following would provide the best evidence for genomic equivalence of all cells within an organism?

A) Observations of determination in an undifferentiated cell
B) Microarray studies showing changes in gene expression
C) Evidence that environmental signals cause differentiation in stem cells
D) Observations of polarity in an early embryo
E) Demonstration of totipotency from a somatic cell

Question 11

A cell that is able to give rise to every cell in the adult body is called a _______ cell.

A) determined
B) pluripotent
C) totipotent
D) multipotent
E) differentiated

Question 12

Which type of cell is most likely to be totipotent?

A) Stem cell from bone marrow
B) Liver cell
C) Larval gut cell
D) Late gastrula cell
E) Early-stage cleavage cell

Question 13

Which type of cell is most likely to be unipotent?

A) Early-stage cleavage cell
B) Pancreatic insulin secreting cell
C) Mesenchymal stem cell
D) Early gastrula cell
E) Stem cell from bone marrow

Question 14

Which statement about cloned animals is true?

A) Cloning of extinct animals has been used to resurrect the wooly mammoth.
B) Cloning has been used to preserve endangered species.
C) Cloning of the sheep "Dolly" demonstrated the efficiency of this method of reproduction,in that all embryos transferred to a surrogate mother survived to birth.
D) Cloning by transferring a nucleus from an embryo into an enucleated egg is less effective than transferring a nucleus from a mammary gland.
E) The cloned sheep named "Dolly" was a clone of the Scottish blackface sheep that gave birth to Dolly.

Question 15

Which statement about development is true?

A) Cell death does not play a role in morphogenesis.
B) Differential gene expression plays an important role in determining cell fate.
C) Throughout development,especially in animals,the range of possible cell fates becomes progressively less restricted.
D) The developmental potential of early embryonic cells is narrower than the potential of cells from more advanced embryos.
E) Cell fate is determined only by informational molecules within a cell and not by signals from surrounding cells.

Question 16

Which is the correct ranking of stem cells with respect to the number of cell types into which they can differentiate (from greatest to least)?

A) Multipotent > pluripotent > totipotent
B) Pluripotent > totipotent > multipotent
C) Pluripotent > multipotent > totipotent
D) Totipotent > pluripotent > multipotent
E) Totipotent > multipotent > pluripotent

Question 17

Hematopoietic stem cell transplantation (HSCT)can be used for cancer patients receiving cancer treatments that kill hematopoietic stem cells.If a patient is going to receive HSCT,

A) hematopoietic stem cells are removed from the patient prior to cancer treatment and transplanted back into the patient following treatment.
B) the patient is treated for cancer,and then hematopoietic stem cells are harvested,grown in culture,and returned to the patient.
C) the patient's own hematopoietic stem cells are treated with radiation to clear them of cancer cells and are then transplanted back into the patient.
D) cancer cells are removed from the patient and grown with hematopoietic stem cells to sensitize the stem cells to the cancer.These cells are then transplanted back into the patient.
E) hematopoietic stem cells from a donor are transplanted into the patient prior to cancer treatment.

Question 18

Which statement about the cloning of Dolly the sheep is true?

A) It established the totipotency of germ cells.
B) Dolly,like all cloned animals,was sterile.
C) Three different sheep were involved;one provided the nuclear material,one supplied the egg,and one served as the surrogate mother.
D) The process involved inducing a mammary gland cell to give rise to a complete embryo.
E) It verified that nuclei from differentiated animal cells carry different DNA than the nucleus of the original zygote from which the animal developed.

Question 19

If you observed the epithelial lining of a developing salivary gland forming a branching tree of ducts and blind-ending sacs,you would know this structure was undergoing

A) gastrulation.
B) determination.
C) apoptosis.
D) induction.
E) morphogenesis.

Question 20

Imagine you are working on a sea urchin embryo after gastrulation has begun.You isolate some of the cells that are inside the blastula.They look unspecialized,but when you culture them in a dish outside of the embryo,they secrete skeletal spicules similar to those they would have eventually formed if they had remained in the embryo.From these results,you could propose that when you isolated these cells,they were already

A) differentiated.
B) undergoing apoptosis.
C) totipotent.
D) fully grown.
E) determined.

Question 21

Different results are achieved when an eight-cell sea urchin embryo is bisected horizontally as opposed to when it is bisected vertically.This observation supports which statement?

A) Cellular determinants are equally distributed in the embryo.
B) Differentiation has occurred by the eight-cell stage.
C) Inducers have determined cell fate by the eight-cell stage.
D) Polarity exists in the embryo by the eight-cell stage.
E) All cells of the eight-cell stage are totipotent.

Question 22

In their studies to create induced pluripotent stem cells,Yamanaka and his coworkers used microarrays in order to

A) reveal DNA sequences that differ between embryonic stem cells and nonstem cells.
B) reveal DNA sequences that differ between hematopoietic stem cells and nonstem cells.
C) reveal gene expression differences between embryonic stem cells and nonstem cells.
D) reveal gene expression differences between hematopoietic stem cells and nonstem cells.
E) induce gene expression in stem cells.

Question 23

In your own body,which tissue is likely to contain the highest amount of multipotent stem cells?

A) Bone marrow
B) Epidermis of the skin
C) Inner lining of the stomach
D) Nerves
E) Muscle

Question 24

Within an egg,there is usually an asymmetry in the distribution of yolk and other factors.This asymmetry indicates that the egg

A) is pluripotent.
B) is determined.
C) has undergone pattern formation.
D) has polarity.
E) has unipotency.

Question 25

The process of cytoplasmic segregation would help to answer which question?

A) How can one reset a differentiated cell such that it can produce many different cell types?
B) How can more than one cell type arise from the single egg cell?
C) What roles do transcription factors play in controlling cell differentiation?
D) How can a skin cell be induced to form a pluripotent stem cell?
E) When is the genome of the embryo activated during development?

Question 26

In your own body,which tissue is likely to contain the least amount of stem cells?

A) Bone marrow
B) Epidermis of the skin
C) Inner lining of the stomach
D) Inner lining of the intestine
E) Nerves

Question 27

The process by which signaling molecules from one tissue (or group of cells)affect the development of adjacent tissue is called

A) cytoplasmic segregation.
B) morphogenesis.
C) transplantation.
D) differentiation.
E) induction.

Question 28

The segregation of cytoplasmic determinants to certain regions within the sea urchin egg cytoplasm is aided in part by

A) induction by cells surrounding the ovulated egg.
B) gene expression in the egg immediately prior to fusion of the egg and sperm.
C) gene expression within the zygote.
D) microfilaments having a growing (plus)end.
E) transport of yolk to the animal half of the egg.

Question 29

Refer to the figure below showing the distribution of cytoplasmic determinants within an embryo undergoing cleavage.If the cells are separated from one another,which cell or combination of cells will most likely to be able to form a complete but smaller than normal embryo?

A) Cell 1
B) Cell 3
C) Cells 1 and 2 combined
D) Cells 3 and 4 combined
E) Cells 1 and 3 combined

Question 30

Refer to the diagram showing the sequence of inductions in the embryonic development of the nematode Caenorhabditis elegans.According to the diagram,you could most likely convert a cell that was supposed to be a secondary vulval precursor cell into an epidermal cell by

A) adding primary inducer.
B) reducing the amount of primary inducer.
C) adding secondary inducer.
D) reducing the amount of secondary inducer.
E) adding a second anchor cell.

Question 31

Which event(s)lead(s)to distinct patterns of gene expression within different cells of an embryo?

A) Unequal distribution of genes among different cells,followed by induction
B) Cytoplasmic segregation and induction
C) Segregation of different chromosomes to different cells
D) Genomic equivalence among all the cells and morphogenesis
E) Segregation of yolk to the animal hemisphere

Question 32

The primary inducer of the vulva in the embryo of the nematode C.elegans is secreted by the _______ cell.

A) primary vulval precursor
B) anal
C) homeotic
D) anchor
E) epidermal

Question 33

If the anchor cell is destroyed in the embryo of the nematode Caenorhabditis elegans,the most likely outcome will be that

A) no vulva will form.
B) no anchorettes will form.
C) secondary vulval precursors will become primary vulval cells.
D) another cell will differentiate into an anchor cell.
E) signals from the nematode's environment will direct epidermal cells to become a vulva.

Question 34

In plants,the cells at the tips of growing roots and stems contain meristems,which are _______ cells.

A) differentiated
B) dedifferentiated
C) pluripotent
D) unipotent
E) multipotent

Question 35

If you were to block expression of the LIN-3 gene in the early embryonic development of the nematode C.elegans,what would be the most likely result?

A) Cells that normally would differentiate into the anus would remain epidermis.
B) More cells than normal would differentiate into the anus.
C) More cells than normal would become anchor cells.
D) Cells that normally would differentiate into epidermis would become vulval precursors.
E) Cells that normally would differentiate into vulval precursors would become epidermis.

Question 36

The "top" of a zygote is often referred to as the _______ pole;the "bottom" is often referred to as the _______ pole.

A) dorsal;animal
B) dorsal;vegetal
C) animal;dorsal
D) animal;ventral
E) animal;vegetal

Question 37

In a hypothetical developmental biology experiment,researchers place a nonporous barrier between the alpha ludens (a made-up structure)and tissues that are supposed to develop into the beta ludens (also a made-up structure).If the beta ludens _______,it is most likely that signals from the alpha ludens are acting as _______ of the beta ludens.

A) develops;inducers
B) develops;microfilaments
C) does not develop;microfilaments
D) develops;transcription factors
E) does not develop;inducers

Question 38

Which statement best describes the differences between embryonic and induced pluripotent stem (iPS)cells?

A) Embryonic stem cells are totipotent,whereas iPS cells are not.
B) IPS cells are totipotent,whereas embryonic stem cells are not.
C) Only iPS cells carry a vector containing extra copies of genes found within the cells.
D) Only embryonic stem cells can be made to match the genome of the patient.
E) IPS cells created from the patient's cells provoke an immune response,whereas donated embryonic stem cells do not.

Question 39

In amphibian eggs,yolk is concentrated in the vegetal half of the fertilized eggs,and the presence of this yolk slows down cell division.Based on this observation,which statement is most likely to be true?

A) Cells in the vegetal half of the embryo will be larger than those in the animal half.
B) Cells in the vegetal half of the embryo will be smaller than those in the animal half.
C) Cells in the animal half and vegetal half of the embryo will be the same size.
D) Amphibian eggs lack polarity.
E) Only the animal half of the egg will go through cell division;the vegetal half will remain undivided.

Question 40

If an eight-cell sea urchin embryo is bisected horizontally,relative to its animal-vegetal axis,

A) both halves will develop into normal,but small,sea urchins.
B) the top half will not develop,while the bottom half will produce a small sea urchin.
C) the top half will not develop,while the bottom half will produce an abnormal half sea urchin.
D) the bottom half will not develop,while the top half will produce an abnormal sea urchin.
E) the bottom half will not develop,while the top half will produce a small,but normal,sea urchin.

Question 41

Use the following to answer questions :
Refer to the figure below showing a stage in limb development in a human embryo.
If the ZPA secreted more morphogen than normal,the most likely result would be

A) two thumbs.
B) five thumbs.
C) five digits but no thumb.
D) no little finger.
E) no digits.

Question 42

If a human fetus is exposed to chemicals that lead to the overexpression of Sonic hedgehog in the ZPAs of the developing arms,the baby will most likely have

A) webbed fingers.
B) two thumbs on each hand.
C) two "little fingers" on each hand.
D) elongated arms.
E) shortened arms.

Question 43

The differentiation of whorls in the flower-forming region of the plant Arabidopsis thaliana is regulated by _______ genes.

A) organ identity
B) dimer
C) whorl locator
D) caspase
E) central axis control

Question 44

In the nematode C.elegans embryo,an overabundance of active ced-3 in cells of the mid region would most likely lead to which result?

A) The cells in that region would become more like those in a more anterior region.
B) The cells in that region would become more like those in a more posterior region.
C) There would be greater apoptosis in that region,which would lead to an overabundance of cells.
D) There would be greater apoptosis in that region,which would lead to a deficiency of cells.
E) There would be less cell death in that region,which would lead to an overabundance of cells.

Question 45

In normal development of the plant Arabidopsis,four whorls of cells create the organs of the flowers.The outermost whorl (whorl 1)produces

A) carpels.
B) petals.
C) stamens.
D) sepals.
E) sepals and stamens.

Question 46

Use the following to answer questions :
Refer to the figure below showing a stage in limb development in a human embryo.
The substance secreted by the ZPA is _______ and the concentration of this is lowest at the region labeled _______.

A) the protein Sonic hedgehog;2
B) the Shh gene;2
C) the transcription factor that turns on the Shh gene;1
D) the ZPA1 protein;2
E) the protein product of the zone of polarizing activity;1

Question 47

Which statement about the organ identity genes in Arabidopsis thaliana is true?

A) They stimulate production of the LEAFY gene.
B) They code for subunits of transcription factors.
C) The products of the genes are only active when three monomers make up a trimer.
D) A loss-of-function mutation in the LEAFY gene results in the formation of more flowers.
E) A loss-of-function mutation in a class A gene causes leaves to form instead of flowers.

Question 48

An increase in the concentration of MyoD would most likely lead to a(n)_______ of p21 expression,which would _______ the activity of cyclin-dependent kinases (CDKs).

A) increase;increase
B) decrease;decrease
C) decrease;increase
D) decrease;have no effect on
E) increase;decrease

Question 49

Which of the following is a Drosophila maternal effect gene?

A) Hunchback
B) Shh
C) Antennapedia
D) Bithorax
E) Bicoid

Question 50

Suppose a laboratory is engaged in genetically modifying a plant to increase the size of its fruit (its carpels).Assuming that organ identity genes play the same roles in this plant that they do in Arabidopsis,_______ the domain of expression of genes in class _______ would most likely yield an increase in fruit size.

A) increasing;A
B) decreasing;A
C) increasing;B
D) decreasing;B
E) decreasing;C

Question 51

Which statement about pattern formation in an embryo is true?

A) It is a process found in animal embryos but not in plant embryos.
B) It involves the French flag protein.
C) It is a pattern imposed on cells after they differentiate.
D) It can involve programmed cell death.
E) It involves transcription factors but does not involve inducers.

Question 52

Lowering the expression of the MyoD gene would tend to _______ the activity of cyclin-dependent kinases (CDKs).This activity would tend to _______ differentiation of muscle cells.

A) increase;enhance
B) increase;retard
C) decrease;enhance
D) decrease;retard
E) decrease;have no effect on

Question 53

In the normal course of development in Arabidopsis,a particular group of cells should develop into carpel tissue.If the expression of class B genes were also induced in those cells,they would develop into _______ tissue.

A) carpel
B) petal
C) stamen
D) sepal
E) carpel and stamen

Question 54

The process that results in spatial organization of an organism or a tissue is called

A) induction.
B) differentiation.
C) apoptosis.
D) determination.
E) pattern formation.

Question 55

In the diagram below,the cell(s)being induced is/are labeled _______ and the inducer is labeled _______.

A) 1;4
B) 3;6
C) 2;4
D) 2 and 3;4
E) 2 and 3;6

Question 56

As the plant Arabidopsis develops,four whorls of cells create the organs of the flowers.The innermost whorl (whorl 4)produces

A) carpels.
B) petals.
C) stamens.
D) sepals.
E) petals and stamens.

Question 57

If a fly embryo has a mutation in one of its _______ genes,this mutation is unlikely to affect its development.

A) gap
B) pair rule
C) maternal effect
D) Hox
E) segment polarity

Question 58

Which statement about development in the fruit fly Drosophila is true?

A) The fates of cells in different segments of the larva are determined before morphological differences are apparent.
B) Cell membranes impede the diffusion of morphogens in the early embryo.
C) Wings develop from segments in the abdomen.
D) The abdomen is more anterior than the thorax.
E) The fate of all cells forming adult structures is determined in the pupal stage.

Question 59

Which statement about the gene MyoD is true?

A) It codes for a transcription factor.
B) It is involved in the differentiation of both animal and plant cells.
C) It is not found in stem cells of adult muscle tissue.
D) It directly inhibits cell division.
E) It induces cell division in muscle stem cells.

Question 60

Which statement about apoptosis is true?

A) It is part of nematode development but not human development.
B) Despite more than 600 million years of evolutionary divergence,humans and nematodes share similar apoptosis pathways.
C) Because apoptosis genes kill cells,evolution selects against apoptosis pathways.
D) Caspases prevent protein degradation that would otherwise lead to cell death.
E) It is the mechanism determining the types of digits that form in the vertebrate limb.

Question 61

Which gene provides an example of the phenomenon of heterochrony?

A) A gene whose expression causes legs to form
B) A gene whose expression inhibits the formation of legs
C) A gene whose expression causes one segment to start growing sooner than it would in the absence of that gene expression
D) A gene whose expression affects more than one module
E) A gene that is expressed in a larger number of cells,causing a larger structure to form

Question 62

Which statement is a general principle of evolutionary developmental biology (evo-devo)?

A) Each group of animals is distinct in the regulatory molecules controlling the animals' development.
B) Embryonic development is protected from environmental influences.
C) A change in the timing of expression of particular genes during development is always lethal and is therefore not a mechanism for evolutionary change.
D) A change in the location of expression of particular genes during development can be a mechanism for evolutionary change.
E) Evolution does not act at the level of the embryo.

Question 63

Mutations in the disheveled gene in Drosophila can lead to various defects in the hairs of the thorax of adult flies,along with misshapen wings.These morphological abnormalities arise because of improper determination of the boundaries of individual segments during the fly's early development.Based on this information,disheveled is most likely a _______ gene.

A) maternal effect
B) gap
C) pair rule
D) segment polarity
E) Hox

Question 64

Which of the following would most likely lead to the development of two heads in a Drosophila embryo,one at each end?

A) Injecting Nanos protein into the posterior region of the egg
B) Knocking out the expression of the bicoid gene in the anterior region of the egg
C) Knocking out the expression of the bicoid gene in the posterior region of the egg
D) Injecting the posterior region of the egg with cytoplasm from the anterior region of another wild-type egg
E) Injecting the anterior region of the egg with cytoplasm from the posterior region of another wild-type egg

Question 65

Female Drosophila that are homozygous for a mutant form of the bicoid maternal effect gene produce eggs that,when fertilized,develop into larvae with no head or thorax.Which procedure would most likely lead to restoration of normal development in one of these mutant eggs?

A) Adding cytoplasm from the anterior end of a normal egg to the anterior end of the mutant egg
B) Adding cytoplasm from the posterior end of a normal egg to the posterior end of the mutant egg
C) Disrupting expression of the mutant bicoid gene in the egg
D) Forcing expression of the nanos gene in the egg
E) Knocking out expression of the nanos gene in the egg

Question 66

Which statement about Hox genes is false?

A) They are part of the so-called genetic toolkit.
B) They are expressed in similar patterns in the embryos of both mice and flies.
C) They are arranged in similar clusters of genes in both mice and flies.
D) Because of their important functional roles,they evolved rapidly in both mammals and flies.
E) They include a conserved region of base pairs called the homeobox.

Question 67

The process by which the relative timing of different developmental processes is altered is called

A) heterotopy.
B) homeosis.
C) developmental plasticity.
D) heterochrony.
E) homeostasis.

Question 68

If Ubx were expressed in the second thoracic segment in Drosophila,the fly would likely develop _______ on the second segment.

A) a new set of wings
B) a larger set of wings
C) a set of halteres
D) eyes
E) antennae

Question 69

Which statement about Hox genes is true?

A) They are a group of maternal effect genes.
B) In Drosophila,inappropriate expression of Antennapedia can cause legs to grow on the head.
C) They code for structural proteins.
D) They are found only in Drosophila and a few closely related genera of flies.
E) Mutations in these genes cause reversal of the anterior-posterior polarity in the early embryo.

Question 70

If you know that the Hox gene AbdB is expressed in the most posterior part of the abdomen in a Drosophila embryo,which conclusion about a homologous gene in humans would most likely be correct?

A) There is no homologous gene in humans,because the evolutionary distance between humans and flies is so great.
B) The homologous gene in humans is expressed only in adults,not in human embryos.
C) The homologous gene is expressed in the head of human embryos.
D) The homologous gene is expressed throughout the human embryo in roughly equal amounts.
E) The homologous gene is expressed near the rump of the human embryo.

Question 71

The expression of hunchback in Drosophila is stimulated by _______ and inhibited by _______.

A) Nanos;Bicoid
B) Nanos;Antennapedia
C) Bicoid;Antennapedia
D) Bicoid;Nanos
E) Antennapedia;Bicoid

Question 72

A gene in Drosophila called even-skipped (eve)received its name because mutations in that gene often lead to embryos that are missing the even-numbered segments.Based on this information,even-skipped is most likely a _______ gene.

A) maternal effect
B) gap
C) pair rule
D) segment polarity
E) Hox

Question 73

Ubx expression _______ wing development and _______ haltere development in dipterans.

A) promotes;promotes
B) promotes;inhibits
C) has no effect on;promotes
D) inhibits;inhibits
E) inhibits;promotes

Question 74

Which statement best describes the relationship between modularity and heterochrony?

A) Heterochrony allows for modularity.
B) Heterochrony inhibits the evolution of modularity.
C) Modularity permits evolutionary changes that involve heterochrony.
D) Modularity inhibits evolutionary changes that involve heterochrony.
E) Modularity has no effect on the likelihood of evolution through heterochrony.

Question 75

In studies of gene expression,which observation would be the least likely?

A) As the result of radically different developmental processes within an insect species,some members of the species have a pair of wings that its conspecifics lack.
B) Expression of a gene that is important in developmental processes varies with temperature.
C) A species of fish is much larger than fish in a closely related species because a gene affecting bone growth is expressed earlier in development in the larger fish than in the related species.
D) The amino acid sequence of a Hox gene protein is extremely similar in nematodes and humans.
E) One rodent species has a narrower face than all others,because in that species the expression pattern of a gene that is important in development is more restricted in its spatial effects.

Question 76

Which sequence represents the correct cascade of gene action in determining the pattern of segmentation in Drosophila?

A) Segment polarity,pair rule,gap
B) Gap,segment polarity,pair rule
C) Gap,pair rule,segment polarity
D) Hox,pair rule,segment polarity
E) Segment polarity,pair rule,maternal effect

Question 77

The _______ thoracic segment of Drosophila bears small outgrowths called halteres that aid in _______.

A) first;balance
B) first;sensation
C) second;sensation
D) second;mating
E) third;balance

Question 78

Drosophila that are homozygous for a loss-of-function mutation of swallow develop normally.If a male that is homozygous for this mutant allele mates with a female that is homozygous for the normal allele,offspring of both sexes develop normally and survive to adulthood.In the reciprocal cross,offspring die before completing early embryonic development because their heads do not develop normally.From this information,one can infer that swallow is most likely a

A) maternal effect gene.
B) Hox gene that acts as a transcription factor to influence the expression of many other genes.
C) segment polarity gene.
D) gap gene that responds to concentrations of a maternal effect gene like bicoid or nanos.
E) pair rule gene.

Question 79

Which statement about Hox genes or their effects on Drosophila is false?

A) Homologous Hox genes encoding similar transcription factors are expressed in similar patterns along the anterior-posterior axes of humans.
B) Full-sized wings in Drosophila are normally produced on just the third thoracic segment.
C) Deletions of the Ubx gene in Drosophila convert the third thoracic segment into the second thoracic segment.
D) Ubx codes for a protein with a homeodomain that binds to the promoter region of target genes.
E) If Ubx is inactivated by a mutation,two sets of wings will develop in the fruit fly.

Question 80

Which class of pattern formation genes is responsible for organizing broad areas along the anterior-posterior axis in the Drosophila embryo?

A) Maternal effect genes
B) Gap genes
C) Pair rule genes
D) Segment polarity genes
E) Hox genes