Bio Test 2

Imagine that you've located a yeast mutant that contains histones resistant to acetylation. What phenotype would you predict for this mutant?

The mutant will show decreased levels of gene expression

What type of mutation would convert a proto-oncogene into an oncogene?

a mutation that greatly increases the amount of the proto-oncogene protein

What methods are utilized by eukaryotes to control their gene expression that is different from the type of control found in bacteria?

control of both RNA splicing and chromatin remodeling

The fact that plants can be cloned from somatic cells demonstrates that

differentiated cells retain all the genes of the zygote

tumor suppressor genes

encode proteins that help prevent uncontrolled cell growth

DNA methylation and histone acetylation are examples of what process?

epigenetic regulation

Forms of the Ras protein found in tumors usually cause what event to occur?

excessive cell division

Oncogenes

genes that cause cancer by blocking the normal controls on cell reproduction

What is the difference between euchromatin and heterochromatin?

heterochromatin is tightly coiled DNA and euchromatin is uncoiled DNA

In the figure at the arrow marked ll, what enzyme is being utilized?

host cell DNA polymerase

What type of bonding is responsible for maintaining the shape of the tRNA molecule?

hydrogen bonding between base pairs

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of cytosine (C) nucleotides in the DNA of promoters of a mammalian system. What result would she most likely see?

inactivation of the selected genes

What is the function of a signal peptide?

it helps target a protein to the ER

What function does the product of the p53 gene carry out?

it inhibits the cell cycle

Under what conditions does the trp repressor block transcription of the trp operon?

when the repressor binds to tryptophan

P-site

where the polypeptide chain is. After the chain on the P-site cleaves and transfers the chain to the A-site (new p-site) the p-site becomes the e-site

Epigenetic control of gene expression at the chromatin level

Acetylation of histones causes chromatin to become loosely coiled, increasing transcription Phosphorylation of histones

What type of molecule is a prion?

A misfolded protein

Which of the following processes correctly describes alternative RNA splicing? A) It can allow the production of proteins of different sizes and functions from a single mRNA B) it can allow the production of similar proteins from different RNAs C) It is a mechanism for increasing the rate of translation D) It increases the rate of transcription

A) It can allow the production of proteins of different sizes and functions from a single mRNA

Which of the following DNA mutations is most likely to damage the protein it specifies? A) a base-pair deletion B) a codon deletion C) a substitution in the last base of a codon D) an addition of three nucleotides

A) a base-pair deletion

Control of gene expression at the RNA level

Alternative RNA splicing produces different mRNAs that will in turn code for different proteins or transcription could stop miRNAs can degrade the mRNA

The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, what would occur?

Anterior structures would form in both ends of the embryo

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true? A) Dna was the first genetic material B) A gene from an organism can theoretically be expressed by any other organism. C) Different organisms have different types of amino acids D) The same codons in different organisms translate into different amino acids

B) A gene from an organism can theoretically be expressed by any other organism.

Which of the following conditions is most likely to cause the lactose operon to be transcribed? A) There is glucose but no lactose in the cell B) The cyclic AMP and lactose levels are both high within the cell C) The cAMP level is high and the lactose level is low D) There is more glucose in the cell than lactose

B) The cyclic AMP and lactose levels are both high within the cell

which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-ile- Val A) 3' -AAA-AAT-ATA-ACA-5' B)3'-AAA-GAA-TAA-CAA-5' C)5'-TTG-CTA-CAG-TAG-3' D)5'-AUG-CTG-CAG-TAT-3'

B)3'-AAA-GAA-TAA-CAA-5'

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, what would be likely?

Beta galactosidase will not be produced

Post-translational modifications of proteins may include which of the following processes? A) addition of a 5' cap B) removal of introns C) addition of carbohydrates to form a glycoprotein D) addition of a poly-A tail

C) addition of carbohydrates to form a glycoprotein

In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated? A) genes coding for enzymes that act in the colon B) genes of the bacteria, which are abundant in the colon C) genes involved in control of the cell cycle D) genes that are especially susceptible to mutation

C) genes involved in control of the cell cycle

Example of a prion associated disease

Cruezfeldt Jakob disease

Which of the following characteristics is typical of the lytic cycle of a bacteriophage? A) the viral genome replicates without destroying the host B) the virus-host relationship usually lasts for generations C) Viral DNA is incorporated into the host genome D) A large number of phages are released at a time

D) A large number of phages are released at a time

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following processes would you expect her to find to have occurred? A) The cell adds a new poly-A tail B) The mRNA attaches to a ribosome and is translated, but more slowly C) The mRNA is quickly converted into a ribosomal subunit D) The molecule is digested by enzymes because it is not protected at the 5' end

D) The molecule is digested by enzymes because it is not protected at the 5' end

Control of gene expression at the protein level

Degradation of proteins get rid of the protein altogether Localization of protein will move the protein to another part of the cell

What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'

Met-Ser-Ser-Leu-Ser-Leu

The genetic code is redundant. What is meant by this statement?

More than one codon can specify the addition of the same amino acid

Will treating a viral infection with antibiotics affect the course of the infection?

No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes

What would be the consequence of a mutation in a bacterial cell that produces a defective aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA?

Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU

Provide three ways that pre-mRNA is modified prior to translation. What is the importance of each modification?

RNA splicing removes introns and puts the exons together so that the mRNA strand will code for the right protein A poly-A tail is added to the 3' end so that the mRNA will not be destroyed by enzymes A 5' cap is added so that the mRNA will not be destroyed by enzymes

Why do RNA viruses appear to have higher rates of mutation?

Replication of their genomes does not involve proofreading

Would heterochromatin or euchromatin be more likely to contain genes that are transcriptionally active?

The euchromatin because transcription will happen faster than when DNA is tightly packed

HIV is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?

The flu virus can be transmitted more easily from person to person than HIV

Why are BRCA1 and BRCA2 considered to be tumor-suppressor genes?

Their normal products participate in repair of DNA damage

What are vaccines are how do they help prevent viral infection?

Vaccines are inactive versions of a virus that stimulate an immune reaction in a person

A-site

a tRNA docks with an amino acid. The anticodon of the tRNA binds to the codon of the mRNA. The A site amino acid forms a peptide bond with the polypeptide chain on the P-site. The peptide chain cleaves and moves to the A-site, which then becomes the new p-site.

Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival by ___?

allowing an organism to adjust to changes in environmental conditions

What are prions?

misfolded versions of normal proteins that can cause disease

What are the three sites on a ribosome that can be occupied by tRNA

p-site e-site a-site

The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.

sets of regulatory proteins

E-site

the tRNA exits the ribosome

Gene expression is often assayed by measuring the level of mRNA produced from a gene. What level of the control of gene expression can be analyzed by this type of assay?

transcriptional control