Gene Regulation and Development

Expression of a liver gene requires a transcription factor that is also required for expression of an eye gene. If liver cells and eye cells have the same transcription factor, why isn't the liver gene expressed in your eye cells? A. Expression of each gene requires a unique combination of multiple transcription factors. B. Your brain "tells" your eye cells not to make liver proteins. C. Your liver cells "tell" your eye cells not to make liver proteins. D. The liver operon is turned off in your eyes. E. Genes for liver proteins are missing from the genomes of the cells of your eyes.

A

In general, the most important step of gene expression for gene regulation in eukaryotes is A. transcription. B. RNA processing. C. translation. D. degradation (break down) of mRNAs. E. degradation (break down) of proteins

A

The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____. A. abdomen B. male flowers C. thorax D. head E. female flowers

A (The abdomen develops where there is a low concentration of bicoid protein.)

Mark ALL answers that apply. Even single-celled organisms like bacteria need to regulate expression of their genes because A. some genes in a bacterium's genome may have opposing functions. B. not all functions of all genes are needed at one time. C. they live in variable environments.

A. X B. X C. X

A hypothetical man has brown hair on the top of his head, yet the hair in his beard is red. The best explanation for this is that cells on his face have _____________ that are different from those in the cells on the top of his head. A. genomes B. transcription factors C. genes D. enhancers and promoters E. numbers of chromosomes

B

Coordinate control (turning multiple genes with related functions on or off at the same time) is important in A. bacteria only. B. bacteria and eukaryotes. C. eukaryotes only. D. no organisms. E. animals but not plants or bacteria.

B

Operons in bacteria and master regulatory genes in eukaryotes are similar in that both A. are always turned on by default. B. enable an organism to turn on multiple genes simultaneously. C. are turned on by activator proteins bound to enhancers. D. produce proteins that are transcription factors. E. consist of multiple genes located next to one another on the same chromosome.

B

What would you expect to see involved in transcription of a gene in eukaryotes but NOT in bacteria? A. a promoter B. a combination of about 10 transcription factors C. RNA polymerase D. RNA nucleotides E. a DNA template

B

Disruption of the gradient of an inducer (i.e., an inductive signal) during an animal's development would NOT be expected to result in A. altered pattern formation. B. altered development along one of the body axes. C. increased numbers of mutations in the animal's DNA. D. abnormal gene regulation in some of the animal's cells. E. missing body parts.

C

Pax-6 is a gene that is involved in eye formation in many invertebrates, such as Drosophila. Pax-6 is found as well in vertebrates. A Pax-6 gene from a mouse can be expressed in a fly and the protein (PAX-6) leads to a compound fly eye. This information suggests which of the following? A. PAX-6 from a mouse can function in a fly, but a fly's Pax-6 gene cannot function in a mouse. B. PAX-6 proteins have identical amino acid sequences. C. Pax-6 is highly conserved and shows shared evolutionary ancestry. D. Pax-6 genes are identical in nucleotide sequence. E. PAX-6 proteins are different for formation of different kinds of eyes.

C

Which of the following do not associate with (i.e., bind to) transcription factors during transcription initiation in eukaryotes? A. enhancers B. promoters C. ribosomes D. additional transcription factors E. RNA polymerase

C

Which of the following does NOT require regulation of gene expression? A. having different cells with different functions B. the development of distinct organs within the body C. turning the synthesis of a protein on and off as needed D. expressing a gene all the time, regardless of conditions E. making the protein hemoglobin only in cells that need to transport oxygen

D

Which of the following is the earliest time when molecules are put in place that can set up major body axes? A. after many cell divisions B. just after fertilization C. after the first cell division of the zygote D. during formation of the egg (before fertilization) E. once the organism has a recognizable adult shape

D

_____ bind(s) to DNA enhancer regions. A. RNA polymerase B. Promoters C. Introns D. Activators E. Exons

D (Activators are a type of transcription factor that bind to enhancer regions.)

The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo. A. the establishment of the right-left axis B. vulval development C. flower development D. the establishment of the anterior-posterior axis E. apoptosis

D (The concentration gradient of bicoid protein determines the anterior-posterior axis of a developing Drosophila.)

Differential gene expression can be established and maintained in an organism by A. cytoplasmic determinants that are distributed unevenly in the unfertilized egg. B. inductive signals from one cell to another. C. gradients of molecules in developing tissues. D. the products of regulatory genes. E. all of these.

E

Genes that are organized in an operon A. are served by one promoter. B. can all be turned on or off at the same time. C. encode proteins with complementary functions. D. are transcribed in one large mRNA. E. all of these answers are correct.

E

If an important cytoplasmic determinant were missing from an animal zygote, what would you expect to happen as the zygote developed into a multicellular organism? A. The animal would lack certain amino acids. B. The animal would lack ribosomes. C. DNA polymerase would be unable to replicate the animal's genome. D. The animal would develop normally. E. One of the animal's major body axes would fail to develop normally.

E