Ch 18 Part 4

Front 1

Formation of the pole cells (the four sequestered cells) demonstrates the role of
A) segmentation genes.
B) homeotic genes.
C) maternal effect genes.
D) zygotic genes.
E) all of the above.

Back 1

maternal effect genes.

Front 2

The next step after the embryo is formed would be
A) division of the embryo into five broad regions.
B) use of pair-rule genes to divide the embryo into stripes, each of which will become two segments.
C) use of zygotic segment polarity genes to divide each segment into anterior and posterior halves.
D) enclosure of the nuclei in membranes, forming a single layer over the surface.
E) separation of head, thoracic, and abdominal segments of the embryo.

Back 2

enclosure of the nuclei in membranes, forming a single layer over the surface.

Front 3

The developmental stages described for Drosophila illustrate
A) a hierarchy of gene expression.
B) homeotic developmental control.
C) the blockage of cell-to-cell communication.
D) homeotic developmental control and the blockage of cell-to-cell communication.
E) a hierarchy of gene expression and the blockage of cell-to-cell communication.

Back 3

a hierarchy of gene expression

Front 4

If she moves the promoter for the lac operon to the region between the beta galactosidase gene and the permease gene, which of the following would be likely?
A) Three structural genes will no longer be expressed.
B) RNA polymerase will no longer transcribe permease.
C) The operon will no longer be inducible.
D) Beta galactosidase will be produced.
E) The cell will continue to metabolize but more slowly.

Back 4

Beta galactosidase will be produced.

Front 5

If she moves the operator to the far end of the operon (past the transacetylase gene), which of the following would likely occur when the cell is exposed to lactose?
A) The inducer will no longer bind to the repressor.
B) The repressor will no longer bind to the operator.
C) The operon will never be transcribed.
D) The structural genes will be transcribed continuously.
E) The repressor protein will no longer be produced.

Back 5

The structural genes will be transcribed continuously.

Front 6

If she moves the repressor gene (lac I), along with its promoter, to a position at some several thousand base pairs away from its normal position, which will you expect to occur?
A) The repressor will no longer be made.
B) The repressor will no longer bind to the operator.
C) The repressor will no longer bind to the inducer.
D) The lac operon will be expressed continuously.
E) The lac operon will function normally.

Back 6

The lac operon will function normally.

Front 7

If she moves the operator to a position upstream from the promoter, what would occur?
A) The lac operon will function normally.
B) The lac operon will be expressed continuously.
C) The repressor will not be able to bind to the operator.
D) The repressor will bind to the promoter.
E) The repressor will no longer be made.

Back 7

The lac operon will be expressed continuously.

Front 8

Which of the following is a likely explanation for the lack of transgene expression in the fifth cell line?
A) A transgene integrated into a heterochromatic region of the genome.
B) A transgene integrated into a euchromatic region of the genome.
C) The transgene was mutated during the process of integration into the host cell genome.
D) The host cell lacks the enzymes necessary to express the transgene.
E) A transgene integrated into a region of the genome characterized by high histone acetylation.

Back 8

A transgene integrated into a heterochromatic region of the genome.

Front 9

Of the lines that express the transgene, one is transcribed but not translated. Which of the following is a likely explanation?
A) no promoter
B) no AUG in any frame
C) no compatible ribosome
D) high histone acetylation
E) missing transcription factor

Back 9

no AUG in any frame

Front 10

In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes

Back 10

decreased chromatin condensation

Front 11

In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes

Back 11

increased chromatin condensation

Front 12

One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes

Back 12

inactivation of the selected genes

Front 13

She tried decreasing the amount of methylation enzymes in the embryonic stem cells and then allowed the cells to further differentiate. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) abnormalities of mouse embryos
D) decreased binding of transcription factors
E) inactivation of the selected genes

Back 13

abnormalities of mouse embryos

Front 14

Within the first quarter hour, the researcher sees that the intact RNA is found in the cells. After 3 hours, she is not surprised to find that
A) Dicer enzyme has reduced it to smaller double-stranded pieces.
B) the RNA is degraded by 5' and 3' exonucleases.
C) the double-stranded RNA replicates itself.
D) the double-stranded RNA binds to mRNAs to prevent translation.
E) the double-stranded RNA binds to tRNAs to prevent translation.

Back 14

Dicer enzyme has reduced it to smaller double-stranded pieces.

Front 15

Some time later, she finds that the introduced strand separates into single-stranded RNAs, one of which is degraded. What does this enable the remaining strand to do?
A) attach to histones in the chromatin
B) bind to complementary regions of target mRNAs
C) bind to Dicer enzymes to destroy other RNAs
D) activate other siRNAs in the cell
E) bind to noncomplementary RNA sequences

Back 15

bind to complementary regions of target mRNAs

Front 16

In addition, she finds what other evidence of this single-stranded RNA piece's activity?
A) She can measure the degradation rate of the remaining single strand.
B) She can measure the decrease in the concentration of Dicer.
C) The rate of accumulation of the polypeptide to be translated from the target mRNA is reduced.
D) The amount of miRNA is multiplied by its replication.
E) The cell's translation ability is entirely shut down.

Back 16

The rate of accumulation of the polypeptide to be translated from the target mRNA is reduced.

Front 17

The researcher in question measures the amount of new polypeptide production in embryos from 2—8 hours following fertilization and the results show a steady and significant rise in polypeptide concentration over that time. The researcher concludes that
A) his measurement skills must be faulty.
B) the results are due to building new cell membranes to compartmentalize dividing nuclei.
C) the resulting new polypeptides are due to translation of maternal mRNAs.
D) the new polypeptides were inactive and not measurable until fertilization.
E) polypeptides were attached to egg membranes until this time.

Back 17

the resulting new polypeptides are due to translation of maternal mRNAs.

Front 18

The researcher continues to study the reactions of the embryo to these new proteins and you hypothesize that he is most likely to see which of the following (while embryonic genes are still not being expressed)?
A) The cells begin to differentiate.
B) The proteins are evenly distributed throughout the embryo.
C) Larval features begin to make their appearance.
D) Spatial axes (anterior → posterior, etc.) begin to be determined.
E) The embryo begins to lose cells due to apoptosis from no further gene expression.

Back 18

Spatial axes (anterior → posterior, etc.) begin to be determined.

Front 19

Which of the following would be his most logical assumption?
A) The substance has moved quickly from region 5 to region 1.
B) Some other material in the embryo is causing accumulation in region 1 due to differential binding.
C) The cytosol is in constant movement, dispersing the polypeptide.
D) The substance is produced in region 1 and diffuses toward region 5.
E) The substance must have entered the embryo from the environment near region 1.

Back 19

The substance is produced in region 1 and diffuses toward region 5.

Front 20

Which of the following best describes this phenomenon?
A) inherited cancer taking a few years to be expressed
B) embryonic or fetal cancer
C) inherited predisposition to mutation
D) inherited inability to repair UV-induced mutation
E) susceptibility to chemical carcinogens

Back 20

inherited inability to repair UV-induced mutation