Biology Test 6: Protein Synthesis

the graph illustrates how

lens cells activate crystallin genes and not albumin genes

Which amino acid has the greatest number of codons?

leu (count)

where is the Exxon

1: line

where is the snRNA

2: tiny string

29-32 where is the splicesome

3 middle

where is the intron

4: 9

The diagram above shows a developing worm embryo at the four-cell stage. Experiments have shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from one another early during the four-cell stage, no intestine will form. Other experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the following is the most plausible explanation for these findings?*

A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.

A single substitution in the third position would have the greatest probability of mutational effect on the codon

AUG

Which structure represents the product of the trp operon?

B: square arrow

Which of the following best represents two different signaling pathways that share a second messenger?

C: X

The replacement of glutamic acid by valine at a specific position in the beta chains of hemoglobin leads to sickle cell anemia. This change represents which of the following mutational events?

DNA base-pair substitution

Some geneticists consider the third base of a codon to be less important than the first two bases as a code for a specific amino acid. All of the following observations would support this hypothesis EXCEPT:

Even though the A is replaced by a G, the triplet UAA will still terminate a polypeptide chain.

What is the best answer for why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged

GENE REGULATION

NEW TEST

Which of the following best describes an event during step 2 in the simplified model shown?

Noncoding sequences are removed from a newly synthesized RNA molecule.

The graph shows the percentage of nuclear transplants embryos that develop normally in relationship to the age of the donor. This graph supports the conclusion.

Older cells have their fates determined and unable to make functional tadpoles

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called

RNA interference

The transcription of DNA to RNA is accomplished by the enzyme

RNA polymerase

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?

Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

If a cell were unable to produce histone proteins, which of the following would be expected to occur?

The cell's DNA couldn't be packed into its nucleus.

Which of the following statements concerning the eukaryotic chromosome is false?

The number of genes on each chromosome is different in different cell types.

The area on a DNA that signals that a gene is near is the

promoter region

Given the codon chart listed below, what would be the effect of a mutation that deletes the G at the beginning of the DNA sequence GCC ...

The reading frame of the sequence would shift, causing a change in the amino acid sequence after that point.

A eukaryotic gene typically has all of the following features except

an operator

Which of the following would result in change in the DNA yet the protein itself is NOT changed?*

base substitution with a silent mutation

Where is tRNA found?

2

Where is a peptide bond made?

4: sun

where is the polypeptide found

5

Based on the information presented, which of the following genetic changes in an individual without diabetes is most likely to result in a disrupted cellular response to insulin signaling similar to that of an individual with type 2 diabetes?

A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein

The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway?

A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger.

DIAGRAM: Which of the following diagrams best represents lipid soluble hormone-activated gene expression?

A,, steroid hormone, recepter m

The first diagram below shows the levels of mRNA from two different genes (bicoid and caudal) at different positions along the anterior-posterior axis of a Drosophila egg immediately before fertilization. The second diagram shows the levels of the two corresponding proteins along the anterior-posterior axis shortly after fertilization. Which of the following conclusions is best supported by the data?

Bicoid protein inhibits translation of caudal mRNA

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP.

Living cells typically have biosynthetic pathways to synthesize at least some of the amino acids used in making proteins. Some strains of E. coli,a prokaryote, can synthesize the amino acid, tryptophan, while other E. coli strains cannot. Similarly, some strains of the yeast S. cerevisiae, a eukaryote, can synthesize, tryptophan, while other S. cerevisiae strains cannot.Which of the following describes the most likely source of genetic variation found in the tryptophan synthesis pathways of both species?

Errors in DNA replication lead to genetic variation.

The table below describes the action of two genes involved in the regulation of nervous system development in the nematode C. elegans. Which of the following claims is best supported by the data?

Gene A promotes neuron development; gene B promotes programmed cell death in neuronal precursors.

Which of the following statements accurately uses the information presented to support the hypothesis that interruption of M function in a single body cell can result in cancer?

Growth-factor signaling can trigger mitosis in cells that are in direct contact with other cells.

Based on the experimental results, which of the following describes the most likely defect in muscle cells of patients with type 2 diabetes?

IRS-1 activation is reduced at high insulin concentrations.

Examine the illustrations showed. What conclusion does this illustration support?

If cells are placed in another location in the organism, and the cells take on the identity of the surrounding tissue, then the cells have not been determined.

In animals, the hox genes encode a family of transcription factors that are important for proper development of embryonic segments and are widely conserved in organisms. The figure below shows the embryonic segments in which one such gene, Hoxc6 is expressed in the embryo of a mouse, a chick, and a goose. Embryonic segments are counted from the anterior end.During the formation of vertebrae, the most anterior embryonic segment that expresses Hoxc6 marks the end of the cervical (neck) vertebrae and the beginning of the thoracic (rib) vertebrae. All mammals have seven cervical vertebrae. Which of the following statements is most likely to be true?

The most anterior expression of Hoxc6 is the eighth vertebra in mammals.

Read the following and answer this question- Which of the following is a valid interpretation of the experimental results that explains how individuals with type 2 diabetes differ from individuals without diabetes?

The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that mobilization of GLUT4 to the cell surface is reduced in muscle cells of those individuals.

Which of the following is a correct statement about mutations?

They are a source of variation for evolution

What could happen to the target cells in an animal that lack receptors for local regulators?

They would not be able to multiply in response to growth factors from nearby cells.

In which of the following would you expect to find the most methylation of DNA?

inactivated mammalian X chromosomes

The fate of a cell during development is

influenced by cytoplasmic determinants.

The role of a metabolite or product that controls a REPRESSIBLE operon is to

bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.

In the yeast signal transduction pathway, after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells,

binding induces changes in the cells that lead to cell fusion.

Steroid hormones produce their effects in cells by

binding to intracellular receptors and promoting transcription of specific genes.

Which structure is needed for the transcription of the enzymes?

c: big circle

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

continuous transcription of the structural gene controlled by that regulator.

Which one of the following mutations would probably produce the greatest change in the activity of the protein for which this gene codes?

deletion of the C at position 5

the graph supports the conclusion

differential gene activation may depend on the presence of certain transcription factors.

Extending the bacterial operon model to developing eukaryotes is difficult because

genes for related function, are often located on different chromosomes.

Which of the following is false about transcription factors?

only prokaryotes employ transcription factors for transcription

One of the best pieces of evidence for the process of gene duplication and mutation is the occurrence of

pseudogenes

All of the following are made up of nucleic acid except a

repressor

The sugar lactose (or allolactose) induces synthesis of the enzyme lactase. What happens when an E. Coli runs out of lactose?

repressor protein binds to the operator

During development, individual cells of the same organism begin to produce different proteins because

specific genes are activated in the cells

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

the active site of an enzyme in the cytoplasm that binds to a specific substrate.

What does the operon model attempt to explain?

the coordinated control of gene expression in bacteria

The lactose operon is likely to be transcribed when

there is lactose but no glucose in the cell.

What is the function of the molecule shown?

to carry the correct amino acid to the mRNA

The tryptophan operon is a repressible operon that is

turned off whenever tryptophan is present in the growth medium.