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Biology & Life Science
Q:
Which human condition is caused by unrepaired UV-induced lesions?
Q:
Recombinational repair is activated when damaged DNA has escaped repair and the distortion disrupts the process of replication. Which gene is responsible recombinational repair?
Q:
The process of error correction of mismatched bases carried out by DNA polymerases is called ________.
Q:
What is meant by the term photoreactivation repair?
Q:
Three human disordersfragile X syndrome, myotonic dystrophy, and Huntington diseaseare conceptually linked by a common mode of molecular upset. Describe the phenomena that link these disorders.
Q:
In a survey of 240,000 human births, six achondroplastic births were recorded to parents who were unaffected. Given that this form of dwarfism is caused by a fully penetrant, dominant, autosomal gene, what is the mutation rate?
Q:
Under certain conditions, the rate of mutation of a particular gene may be determined in humans. What three properties of the mutation would favor the most direct determination of mutation rate in humans?
Q:
It has been found that a particular "+ " combination of frameshift mutations in gene X gives a wild-type phenotype, whereas a " +" combination gives a mutant phenotype, even though the sites of insertion/deletion are the same. How might these results be explained?
Q:
Recent discoveries on causes of fragile X syndrome, myotonic dystrophy, and Huntington disease indicate which type of genetic alteration?
Q:
Assuming one mutational event in a gene, on average, which of the following mutagens or mutational conditions would be expected to cause the most damage to a protein synthesized by such a mutagenized gene: 5-bromouracil, 2-amino purine, ethylmethane sulfonate, or frameshift?
Q:
When X-rays penetrate cells, electrons are ejected from atoms of molecules. Stable molecules can be transformed into which two types of hazardous materials?
Q:
What is the common influence of ultraviolet light on DNA?
Q:
Considering the electromagnetic spectrum, identify likely mutagens from the following list: radio waves, microwaves, infrared, ultraviolet, X-rays, gamma rays, cosmic rays.
Q:
Some mutagens cause genetic changes that can be "corrected" by reexposing cells to the same mutagen. Other mutagens do not behave in this way. Provide one example of each of these two types of agents and describe the mutational changes caused in DNA. Explain why some mutagens behave in one way, while others do not.
Q:
Describe the mutagenic action of the following two mutagens: 5-bromouracil and ultraviolet light.
Q:
A mutation that occurs naturally, without exposure to a known mutagen, is called a(n) ________.
Q:
Apurinic sites (AP sites) involve a spontaneous loss of a(n) ________ in an intact double-helix DNA molecule.
Q:
DNA may be damaged from the by-products of normal cellular aerobic respiration. Name three of these electrophilic oxidants that are generally classified as reactive oxidants.
Q:
In general, mutation rates in humans occur in the range of ________ (frequency) per gamete per generation.
Q:
One type of mutation involves the replacement of a purine with a purine, while another causes the replacement of a pyrimidine with a purine or the reverse. What general terms are associated with these two mutational phenomena?
Q:
Assume that a new mutation occurs in the germ line of an individual. What finding would suggest that the new mutation is dominant rather than recessive?
Q:
Three major types of RNAs are mRNA, rRNA, and tRNA. For each of the conditions below predict the consequences in terms of the population of proteins being synthesized in a particular cell. What qualitative and quantitative changes, if any, are expected in the individual protein involved (if one is involved) and in the population of proteins produced in that cell?
a) A frameshift mutation in mRNA. The condition is heterozygous in the involved cell.
b) A deletion (homozygous) that removes approximately half of the rRNA genes.
Q:
How was it determined that X-rays are mutagenic?
Q:
Mutations may exert a variety of effects on living systems. List at least three categories of mutations based on their biological effects.
Q:
Under which condition(s) might one have an amino acid substitution in a protein that does not result in an altered phenotype?
Q:
List five general categories of mutation.
Q:
Barbara McClintock discovered mobile elements in corn by analyzing the genetic behavior of two elements, Ds and Ac. The interplay between these two elements has become one of the most interesting stories of discovery in the field of genetics. How do Ds and Ac interact?
A) Ds causes a deletion next to the insertion site of Ac.
B) Ac causes a deletion next to the insertion site of Ds.
C) While Ds moves only if Ac is present in the genome, Ac is capable of autonomous movement.
D) The movement of Ac is dependent on two forms of Ds.
E) Both elements can move only within chromosome 9.
Q:
Some bacterial transposons, known as Tn elements, are larger than insertion sequences (IS elements) and contain protein-coding genes that have human health significance. What might such a bacterial transposon contain?
A) drug resistance
B) oncogene
C) pseudogene
D) proto-oncogene
E) dissociation element
Q:
All insertion sequences (IS elements) contain two structural elements that are essential for their movement. What are these two elements?
A) transposase and inverted terminal repeats
B) integrase and pseudogenes
C) integrase and oncogenes
D) proto-oncogenes and oncogenes
E) transposase and oncogenes
Q:
Transposons, or jumping genes, are DNA elements that move within the genome. In which organismic groups are transposons found?
A) bacteria
B) eukaryotes
C) mammals
D) ancient bacteria
E) all organismic groups
Q:
Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates. Such individuals are likely to suffer from ________.
A) xeroderma pigmentosum
B) SCID
C) phenylketonuria
D) muscular dystrophy
E) Huntington disease
Q:
Which of the following name two mutagens that would be classified as base analogs?
A) acridine orange and proflavine
B) ethylmethane sulfonate and ethylmethylketone peroxide
C) ultraviolet light and cosmic radiation
D) 5-bromouracil and 2-amino purine
E) hydroxyurea and peroxidase
Q:
Mutations that arise in nature, from no particular artificial agent, are called ________.
A) oblique mutations
B) induced mutations
C) spontaneous mutations
D) chromosomal aberrations
E) cosmic mutations
Q:
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.
A) base analogs and frameshift
B) error prone and spontaneous
C) transversions and transitions
D) euchromatic and heterochromatic
E) sense and antisense
Q:
A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?
A) base analog
B) transversion
C) transition
D) frameshift
E) recombinant
Q:
Conditional mutations are more likely to result from a mutation caused by which of the following alterations to the coding region of a gene?
A) four bases added within a short region of a gene
B) base addition
C) X-rays
D) deletion
E) tautomeric shift
Q:
Nutritional mutations can be defined as ________.
A) those mutations that do not allow a bacterium or fungus to grow on minimal medium but do allow growth on complete medium
B) those mutations that change the composition of the medium
C) those mutations belonging to the group called prototrophs
D) those mutations caused by site-specific mutagenesis
E) all strains that are not auxotrophic
Q:
Exon shuffling is a term used to describe the movement of modular protein domains during protein evolution. As a result different genes specify similar domains.
Q:
Different domains in proteins impart different functional capabilities.
Q:
The primary structure of a protein is composed of the sequence of amino acids in that protein.
Q:
The secondary structure of a protein is dependent on polar interactions among the side chains of the amino acids.
Q:
Proteins are composed of strings of nucleotides connected together by 5-²-3-² phosphodiester bonds.
Q:
Sickle-cell anemia is caused by the absence of the alpha chain of hemoglobin.
Q:
When a metabolic block occurs in a biochemical pathway, it is common for amount of the substance immediately prior to that block to increase.
Q:
Prokaryotic and eukaryotic ribosomes are structurally and chemically identical.
Q:
rDNA is the portion of a genome that is involved in the production of ribosomal RNA.
Q:
The ribonucleic acid components known to exist in eukaryotic ribosomes are the following: 5.8S, 18S, 28S, and 5S.
Q:
Which class of protein functions primarily by lowering the energy of activation during a reaction?
Q:
List at least three posttranslational modifications known to occur as a newly synthesized protein matures.
Q:
Considering the types of side chains on amino acids and their relationship to protein structure, where are the amino acids with hydrophobic side chains most likely to be located?
Q:
Regarding the protein structure, how are β-pleated sheets arranged and stabilized?
Q:
Assuming that an amino acid sequence is 250 amino acids long, how many different molecules, each with a unique sequence, could be formed?
Q:
Below are several phenomena relating to protein structure. Clearly describe each phenomenon, the conditions under which each occurs, and the probable influence each has on protein structure.
(a) hydrophobic interactions
(b) hydrogen bonds
(c) disulfide bridges
Q:
In what ways do the amino acid side chains interact to influence protein function?
Q:
What is the structure of fetal hemoglobin (HbF)?
Q:
What is the general ethnic distribution of the sickle-cell gene?
Q:
Describe the basic structure of normal adult hemoglobin and the abnormality observed in sickle-cell hemoglobin.
Q:
Electrophoretic separation of HbA from HbS is based on a difference in their ________.
Q:
A procedure that is often used to separate molecules by using their molecular charges is called ________.
Q:
Studies of Neurospora led to the ________ statement, whereas studies of human hemoglobin led to the ________ statement.
Q:
Nutritional mutants in Neurospora can be "cured" by treating the medium with substances in the defective metabolic pathway. What determines whether the mutant strain (auxotroph) is "cured" by a particular substance?
Q:
Much has been learned about the relationship between genes and gene products through the use of the mold Neurospora. What specific attributes make Neurospora a good organism for such studies?
Q:
The problem below relates to the synthesis of several intermediates in the citric acid cycle, which is essential in the production of ATP through aerobic respiration. A set of experimental results relating the growth (+) of Neurospora on several media is given in the table. Based on the information provided, present the biochemical pathway for the substances oxaloacetate, fumarate, malate, and succinate, and the locations of the metabolic blocks produced by the various strains.
Q:
The accompanying table is a set of experimental results relating the growth (+) of Neurospora on several media (MM = minimal medium). Based on the information provided, present the biochemical pathway and the locations of the metabolic blocks.
Q:
Describe the conceptual basis for constructing biochemical pathways using nutrient supplement experiments with Neurospora.
Q:
The following table presents the effect of different media on the growth response of tryptophan mutations in Salmonella typhimurium (+ = growth, - = no growth). (a) Construct the biochemical pathway for the compounds IGP, AA, IN, and TRY based on these data.
(b) Place strains of bacteria (mutations) in the appropriate steps in the pathway.
(c) In bacteria it is often possible to make partial diploid strains. Assume that a diploid strain was made containing the complete genomes of the trp-2 and trp-1 strains. Would this diploid strain be able to grow on the unsupplemented medium? Explain your answer.
Q:
Given the accompanying table: Where numbers 1 through 4 indicate four supplements that must be added to sustain growth of the organism. Determine a possible metabolic pathway that would give the results seen for the four mutant strains, A through D.
Q:
Early in the 1900s, Sir Archibald Garrod studied a number of metabolic defects in humans. One particular disorder involved the inability to metabolize homogentisic acid. What is the name of this disorder?
Q:
What are polyribosomes?
Q:
Three major types of RNAs are mRNA, rRNA, and tRNA. For each of the conditions below, predict the consequences in terms of the population of proteins being synthesized in a particular cell. What qualitative and quantitative changes, if any, are expected in the individual protein involved (if one is involved) and in the population of proteins in this cell?
(a) An acridine dye-induced mutation (adds or deletes single bases in DNA) leads to an mRNA for one protein-producing gene. The condition is heterozygous in the involved cell.
(b) A deletion (homozygous) that removes approximately half of the rRNA genes.
Q:
Knowing that the base sequence of any given messenger RNA is responsible for precisely ordering the amino acids in a respective protein, present two mechanisms by which intrinsic properties of mRNA may regulate the "net output" of a given gene.
Q:
The accompanying drawing represents simultaneous transcription and translation in E. coli. The direction of the RNA polymerase is given by the arrow.(a) Is the letter A nearer the 5-² or the 3-² end of the molecule?(b) Is the letter B nearer the 5-² or the 3-²' end of the molecule?(c) Is the letter C nearer the 5-² or the 3-²' end of the tRNA molecule?(d) What is the "S" value for the large rRNA that is closest to the letter D?(e) Which terminus (N or C) of the growing polypeptide chain is nearer to the letter E?
Q:
Draw and label the spatial and polarity relationships among the following translational components: ribosome (small and large subunits), growing polypeptide chains, amino acid attachment to tRNA, mRNA, codon, and anticodon.
Q:
During translation, which triplets signal chain termination?
Q:
Assume that a base addition occurs early in the coding region of a gene. Is the protein product of this gene expected to have more or fewer altered amino acids compared with the original gene with a base deletion late in the coding region?
Q:
Describe each of the following parameters that relate to the structure and function of tRNA:
(a) four functional domains
(b) Wobble hypothesis
Q:
Which protein class directly controls many of the metabolic reactions within a cell?
A) structural proteins
B) repressor proteins
C) operator proteins
D) enzymes
E) hydrophilic proteins
Q:
Side groups of amino acids are typically classified under which of the following?
A) polar, nonpolar
B) linear, circular
C) alpha, omega
D) long, short
E) primary, secondary
Q:
The secondary structure of a protein includes ________.A) gamma and deltaB) alpha and gammaC) -helix and -pleated sheetD) hydrophobic clustersE) disulfide bridges
Q:
The primary structure of a protein is determined by ________.
A) the sequence of amino acids
B) hydrogen bonds formed between the components of the peptide linkage
C) a series of helical domains
D) pleated sheets
E) covalent bonds formed between fibroin residues