Deck 19: The Genetic Analysis of Development

Question 1

In primary mutant screens,

A)mutant flies are identified by morphology and then the mutant genes are isolated and studied.
B)mutant flies are created by RNAi using random RNA sequences and then the genes affected identified.
C)mutant flies are created by gain-of-function expression of random genes.
D)two mutant flies are mated to determine if there is an effect on morphology.

Answer 1

A

Question 2

Which of the following is the least important characteristic that geneticists look for in a model organism?

A)ease of cultivation
B)rapid reproduction
C)small size
D)small genome

Answer 2

D

Question 3

The presence of a homeodomain in a protein suggests what about its function?

A)It has kinase activity.
B)It is a membrane bound receptor.
C)It is a secreted protein.
D)It is a transcription factor.

Answer 3

D

Question 4

In Drosophila, two maternal transcripts that are distributed evenly throughout the oocyte prior to fertilization are

A)caudal and knirps.
B)bicoid and nanos.
C)caudal and hunchback.
D)sevenless and even-skipped.

Question 5

The observation that ________ provides evidence that all living forms are related.

A)some organisms use mosaic determinism, whereas others use regulative determinism
B)only histone genes are conserved
C)many genes and genetic pathways are conserved
D)sex determination occurs by different mechanisms in many species

Question 6

A temperature-sensitive (ts)mutation is often due to a ________ mutation that affects protein folding or activity.

A)null
B)nonsense
C)missense
D)silent

Question 7

Which of the choices gives the correct sequence of early embryonic development in Drosophila?

A)zygote, syncytial blastoderm, multinucleate syncytium, cellular blastoderm
B)zygote, cellular blastoderm, syncytial blastoderm, multinucleate syncytium
C)zygote, multinucleate syncytium, syncytial blastoderm, cellular blastoderm
D)syncytial blastoderm, multinucleate syncytium, zygote, cellular blastoderm

Question 8

Which statement best describes the limitations of using of humans in genetic studies of developmental biology?

A)The variation in human development between individuals is too large for genetic studies.
B)It is impractical and unethical to conduct experimental manipulation or targeted mutagenesis of humans to examine the role of genes in development.
C)It is impractical and unethical to examine and describe abnormalities of human development, such as birth defects.
D)Genetic studies of human development are not necessary, because most problems in human development are due to environmental influences and not genetics.

Question 9

Nurse cells surround Drosophila oocytes and produce maternal mRNA and proteins that are deposited into the egg.Which of the following products would be produced by nurse cells?

A)bicoid mRNA
B)Antp mRNA
C)Caudal protein
D)Hedgehog protein

Question 10

What is the most significant advantage of using RNAi to study development?

A)Geneticists have only been able to identify a subset of the genes involved in development.
B)Genetic studies of a single gene can be completed without creating new mutant organisms.
C)RNA is easy to isolate.
D)RNAi causes phenotypes not typical of in vivo development.

Question 11

Maternal effect mutations can be identified when

A)homozygous mutant females exhibit an abnormal phenotype, whereas mutant males appear wild-type.
B)homozygous mutant females can develop normally, but their offspring exhibit a mutant phenotype.
C)heterozygous mutant females can develop normally, but their offspring exhibit a mutant phenotype.
D)any aspect of embryonic development is abnormal.

Question 12

The Aniridia gene in humans is involved in eye formation.Although eye development is very different in flies, this gene is highly conserved.What is the Drosophila homolog of Aniridia?

A)eyeless
B)Pax-6
C)noeye
D)ommatidia

Question 13

A researcher performs RNAi against a gene that is required for viability in C.elegans embryos and 70% of the embryos die during development.Some of the embryos may have survived because

A)RNAi did not eliminate the mRNA (and protein)of the gene completely.
B)the dsRNA was used to translate additional proteins to compensate for the mRNA that was degraded.
C)RNAi eliminated the protein product of the gene.
D)of issues related to fertilization.

Question 14

A molecule whose concentration determines the developmental fate of a cell is called

A)monomorphic.
B)a maternal effect gene.
C)a signaling molecule.
D)a morphogen.

Question 15

What is a major advantage of using a modifier screen as opposed to a primary screen?

A)Modifier screens can be used to identify pleiotropic genes.
B)Modifier screens are easier to perform.
C)Modifier screens use a random selection of flies based on their morphology and therefore should identify all genes involved in development.
D)Modifier screens are performed with chemically mutagenized flies so all genes that affect development should be identified more rapidly than screening for spontaneous mutants.

Question 16

How do genetic mosaics help determine the focus of action of a gene?

A)Mosaics are composed of cells with different genotypes, so the phenotype of the cells that lack a gene product can be compared to that of neighboring cells that have the gene product.
B)Mosaics are created by mating flies that are homozygous recessive for two different genes and the morphology of the double mutant progeny is studied.
C)Mosaics are created by mating two flies that carry homozygous gain-of-function mutations in different genes and the effects of the mutations on the morphology studied.
D)Mosaics are created by the Cre-loxP system which allows for the deletion of specific genes at controlled stages of development.

Question 17

How would you best follow the timing of expression of a given protein during development in a live animal?

A)in situ hybridization
B)RT-PCR
C)using a transgenic organism that expresses a GFP fusion protein
D)microarray analysis
E)using antibodies against the protein of interest

Question 18

A homeodomain is a region within a protein that

A)acts as a receptor.
B)has kinase activity.
C)binds to specific base pair sequences.
D)binds to transcription factors.

Question 19

Which of the following is a zygotic gap gene in Drosophila?

A)knirps (kni)
B)even-skipped (eve)
C)caudal (cad)
D)hedgehog (hh)

Question 20

RNAi

A)depletes the mRNAs of specific genes.
B)uses dsRNA to bind to transcription factors.
C)can be used to create functional knockin mutants.
D)is not useful for the study of development.

Question 21

Gene order can be inferred from gene expression patterns because

A)an upstream gene can affect downstream gene expression.
B)mRNAs for proteins in a pathway are produced at the same time, but then are translated only when the proteins are needed.
C)proteins in a pathway are produced at the same time but the proteins that are not needed are degraded.
D)mRNAs for proteins in a pathway are produced at the same time and those that are not needed are destabilized by miRNAs.
E)gene expression does not depend on upstream genes.

Question 22

How were mutants used to order the sevenless-Ras pathway?

A)Cells that expressed a constitutively active Ras mutant protein did not require Sevenless activation to become R7.
B)Cells that expressed a constitutively active Sevenless mutant protein did not require Ras activation to become R7.
C)Cells that expressed an inactive Ras mutant protein did not require Sevenless activation to become R7.
D)Cells that expressed a constitutively-inactive Sevenless mutant protein did not require Ras activation to become R7.

Question 23

The pattern of embryonic expression for a specific gene shown by RNA in situ hybridization and a GFP fusion protein will always be identical.

Question 24

Which statement describes a primary mutant screen?

A)A researcher uses CRISPR to create mutations in mouse homologs of three genes that function in heart development in the fruit fly.
B)A scientist uses RNAi to simultaneously knock down the expression of two genes in C.elegans to determine whether they function redundantly.
C)A scientist examines a large number of mutagenized zebrafish embryos for abnormalities in blood vessel formation.
D)A researcher treats a large number of Arabidopsis plants with different chemicals to determine which chemicals inhibit plant growth.

Question 25

Expression of homeotic genes

A)assigns a unique identity to each segment.
B)defines anterior and posterior ends of the fly.
C)controls the expression of the segment polarity genes.
D)subdivides the embryo into a precise number of segments.

Question 26

How are temperature sensitive mutants used to determine when genes act during development?

A)Embryos can be shifted to the restrictive temperature to inactivate the mutant gene and the effect of inactivation on subsequent stages can be observed.
B)Embryos can be shifted to the permissive temperature to inactivate the mutant gene and the effect of inactivation on subsequent stages observed.
C)Embryos can be incubated at the restrictive temperature for several hours.If the embryo develops normally, then the gene product is required during that period of development.
D)Embryos can be raised at the permissive temperature and if the embryo does not die, then the gene product is not required for development.

Question 27

What is the order of action of these classes of genes during Drosophila development?

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