Genetics exam 2
If the sequence of an RNA molecule is 5'-GGCAUCGACG-3', what is the sequence of the nontemplate (aka coding) strand of DNA? 'A) 5'-GGCATCGACG-3 B) 3'-GGCATCGACG-5' C) 5'-CCGTAGCTGC-3' D) 3'-CCGTAGCTGC-5' E) 3'-CGTCGATGCC-5'
'A) 5'-GGCATCGACG-3
An operon is: A) A set of related genes in bacteria that are transcribed as a single unit. B) A non-coding sequence that interrupts the open reading frame of proteins C) The coding sequence in the open reading frame of eukaryotic proteins D) The site where repressor proteins bind to decrease transcription E) None of the above
A) A set of related genes in bacteria that are transcribed as a single unit.
In which functional site of the ribosome do newly incoming tRNAs carrying amino acids enter (with the exception of the first amino acid)? A) A site B) P site C) E site D) T site E) None of the above
A) A site
The human gene encoding for calcitonin contains six exons and five introns and is located on chromosome 11. The pre-mRNA transcript from this gene can generate either calcitonin or calcitonin gene related peptide (CGRP) in a tissue-specific manner. Calcitonin produced from the thyroid gland is 32 amino acids long and functions to regulate the calcium while CGRP, which contains 37 amino acids, is produced by the brain cells and involved in transmission of pain. Which of the following processes makes production of two functionally and structurally different proteins from the same gene possible? A) Alternative splicing of the calcitonin gene B) 5' capping of only calcitonin C) Only CGRP contains AU-rich elements D) Riboswitch located upstream of the calcitonin gene E) RNA interference
A) Alternative splicing of the calcitonin gene
Which of the following are generally collinear with regards to gene expression? A) Bacterial structural genes B) Eukaryotic structural genes C) Both bacterial and eukaryotic structural genes D) Neither bacterial nor eukaryotic structural genes
A) Bacterial structural genes
A helix-turn-helix motif is found in general as well as regulatory transcription factors. This structural motif helps these proteins do which of the following? A) Bind DNA B) Interact with other proteins C) Bind aptamers D) Dissociate the RNA-DNA hybrid to end transcription E) Interact with the ribosome
A) Bind DNA
How would you expect deletion of a checkpoint protein such as brca1 to contribute to cancer development? A) Cancer would proliferate easier as DNA damage would not be detected prior to cell division B) Cancer would cease to spread as the cell would stop dividing C) Deletion of a checkpoint protein would most likely have no effect on cancer development
A) Cancer would proliferate easier as DNA damage would not be detected prior to cell division
Which of the following is the best example of a metastasis? A) Colorectal cancer spreads to the liver and lungs, resulting in liver and lung cancer B) Breast cancer begins as a one tumor cell but then invades healthy breast tissue C) One brain cell undergoes a genetic change D) Bone cancer stops spreading following chemotherapy treatment
A) Colorectal cancer spreads to the liver and lungs, resulting in liver and lung cancer
A DNA sequence is exposed to X-rays during interphase (after synthesis, prior to mitosis), resulting in DNA breaks. Which of the following systems could be used to repair this type of mutation? A) Homologous recombination repair B) Non-homologous end joining C) DNA mismatch repair D) Base excision nucleotide repair E) None of the above
A) Homologous recombination repair
Which of the following scenarios would represent a repressible gene under positive control? A) Inducer molecule binding to a repressor protein, resulting in its inactivation B) Co-repressor molecule binding to a repressor protein, allowing it to decrease gene expression of its target operon C) Inducer molecule binding to an activator protein, allowing it to increase gene expression of its target operon D) Inhibitor molecule binding to an activator protein, resulting in its inactivation E) None of the above
A) Inducer molecule binding to a repressor protein, resulting in its inactivation
The genetic code is said to be degenerate, which means: A) More than one codon can specify a single amino acid B) More than one amino acid can specify a single codon C) More than one stop codon can be used D) The start codon is almost always the same, AUG E) Over time, the DNA sequence of an individual mutates until it is not functional
A) More than one codon can specify a single amino acid
Luke Gigord and colleagues studied flower color polymorphism in Elderflower orchids. Some flowers are purple and some are yellow, normally at about 50% of each in a given population. The fitness of yellow flowers was highest when purple flowers were common, and vice-versa. This is an example of: A) Negative frequency-dependent selection B) Disruptive selection C) Bottleneck effect D) Stabilizing selection E) Directional selection
A) Negative frequency-dependent selection
Polyribosomes that allow for coupling of transcription and translation occur in: A) Prokaryotes only B) Eukaryotes only C) Both prokaryotes and eukaryotes D) Neither prokaryotes nor eukaryotes
A) Prokaryotes only
In eukaryotes, which of the following is located in the core promoter, allowing for basal transcription? A) TATA box B) Silencer C) Enhancers D) Sine-DelGarno sequence E) All of the above
A) TATA box
In a cloning experiment, you insert a target gene into a vector containing a lacZ gene such that the lacZ gene is disrupted. If the transformed cells are grown on X-Gal and IPTG, which colonies would contain the recombinant vector? A) The white colonies B) The blue colonies C) Half of the total colonies D) Both the white and the blue colonies E) None of the colonies
A) The white colonies
Viral integration enhances the expression of nearby proto-oncogene myc. How would you expect this event to contribute to cancer development? A) This event would promote cancer B) This event would decrease the instance of cancer C) This event would have no effect on cancer development
A) This event would promote cancer
A 2+3 stem-loop in the trpL mRNA (leader peptide) would allow for which of the following? A) Transcription of the trp structural genes when tryptophan is absent B) Transcription of the trp structural genes when tryptophan is present C) Attenuation of the trp structural genes when tryptophan is absent D) Attenuation of the trp structural genes when tryptophan is present E) No effect, as 2+3 stem-loop does not affect transcription of the trp operon in Escherichia coli
A) Transcription of the trp structural genes when tryptophan is absent
The allele frequency for a given gene is 1.0. True or False, the given gene is a monomorphic gene. A) True B) False
A) True
True or False, a cancerous growth is considered to be clonal. A) True B) False
A) True
True or False, monozygotic twins are more likely to share a genetic disease than dizygotic twins. A) True B) False
A) True
True or False, most cancers involve multiple genetic changes. A) True B) False
A) True
Which of the following is an example of bioremediation? A) Using Deinococcus radiodurans can cleanup toxic radioactive waste B) Using Agrobacterium radiobacter to prevent crown gall disease caused by Agrobacterium tumefaciens C) Using Escherichia coli to synthesize human insulin D) Using Bacillus thuringiensis toxins to kill plant pests such as caterpillars and beetles E) Spraying plants with genetically-modified bacteria that produce ice crystals as a way to reduce frost damage
A) Using Deinococcus radiodurans can cleanup toxic radioactive waste
Which of the following best describes the role of mediator? A) A protein complex that scans the DNA and binds to the promoter to initiate transcription in prokaryotes B) A protein complex that moderates the interaction between regulatory transcription factors and RNA polymerase II in eukaryotes C) A protein complex that allows for the termination of translation in eukaryotes D) A protein complex that allows for the termination of transcription in prokaryotes E) A protein complex that allows for the termination of translation in prokaryotes
B) A protein complex that moderates the interaction between regulatory transcription factors and RNA polymerase II in eukaryotes
In the E. coli lac operon, which of the following molecules binds directly to the lac repressor protein, thus serving as an inducer molecule? A) Lactose B) Allolactose C) cAMP D) CRP E) Tryptophan
B) Allolactose
Which of the following mechanisms regulates genes at the level of translation (i.e. it can prevent or allow for translation to start)? A) Attenuation B) Antisense RNA C) Feedback inhibition D) ATP-dependent remodeling complex E) All of the above
B) Antisense RNA
Huntington disease can strike at an earlier age and bring about a more rapid degeneration and death in successive generations within a family. This phenomenon can be explained by which mechanism? (Hint: Close inspection of the mutated Huntington protein shows protein aggregation due to an increased number of lysines within the coding sequence.) A) Chronic exposure to mutagens in the environment B) Expansion of a trinucleotide repeat in the coding sequence of the gene C) Somatic cell mutation D) Absence of a gene product that is involved in DNA repair E) Reversion
B) Expansion of a trinucleotide repeat in the coding sequence of the gene
True or False, beneficial mutations are the most common type of mutation. A) True B) False
B) False
True or False, genetic drift affects large and small populations equally. A) True B) False
B) False
True or False, methylation of DNA sequences called CpG islands typically increases transcription. A) True B) False
B) False
True or False, molecular pharming is the process by which DNA is harvested from organisms for the purpose of designing pharmaceutical drugs tailored for an individual's need. A) True B) False
B) False
True or False, reproductive cloning is a strategy used to produce large amounts of mammalian proteins from the mammary glands of transgenic agricultural animals such as cattle. A) True B) False
B) False
True or False, the majority of cancers are inherited. A) True B) False
B) False
True or False, the mutation rate of a given gene is constant, and cannot be changed even in the presence of mutagens. A) True B) False
B) False
Following cellular damage (such as double strand breaks), p53 activates all of the following genes except? A) Genes encoding DNA repair enzymes B) Genes encoding cellular growth factors C) Genes encoding caspases D) p53 activates all of these genes E) p53 does not activate any of the above genes
B) Genes encoding cellular growth factors
Which of the following is/are a valid concern(s) to the liposome-method of delivery for gene therapy? A) Liposomes elicit an immune response B) Liposomes have a low efficiency for gene delivery C) Liposomes can transform proto-oncogenes into oncogenes D) Liposomes can proliferate after entry into host cells E) All of the above are valid concerns
B) Liposomes have a low efficiency for gene delivery
Which of the following chemical mutagens is an alkylating agent? A) Nitrous acid B) Nitrogen mustard C) Proflavin D) 5-bromouracil E) Acridine dyes
B) Nitrogen mustard
Suppose a research study shows that people who suffer from severe depression are homozygous for a mutation in the hypothetical DEP gene. Individuals without this form of depression have the following template sequence at the beginning of the translated region of their DEP genes Normal: 3-TAC TGC AAA CTT TAA GTC AGA TCT -3. Affected individuals have the following template sequence Affected: 3-TAC TGC AAA CTT TAA ATC AGA TCT-3. Using the codon table below, the mutation identified is a: A) Missense mutation B) Nonsense mutation C) Silent mutation D) Frameshift E) Deletion
B) Nonsense mutation
Which of the following statements is FALSE concerning the modern definition of natural selection? A) Individuals with beneficial alleles are more likely to survive and reproduce B) Over the course of a single generation, allele frequencies will change through natural selection C) Some alleles encode proteins that increase an individual's survival or reproductive capacity D) Distinct alleles may encode proteins of differing functions E) Within a population, there is allelic variation arising from various factors such as mutations causing different DNA sequences
B) Over the course of a single generation, allele frequencies will change through natural selection
In eukaryotes, which RNA polymerase transcribes the genes that encode proteins? A) RNA polymerase I B) RNA polymerase II C) RNA polymerase III D) RNA polymerase IV E) RNA polymerase V
B) RNA polymerase II
What is the function of DNA N-glycosylases? A) Recognize and cleave phosphodiester bonds in DNA B) Recognize and remove modified bases from the sugar component of DNA C) Reattach the two parts of DNA that result from double-strand breaks D) Remove pyrimidine dimers from DNA of E. coli that result from exposure to UV light E) Prevent strand slippage during DNA replication
B) Recognize and remove modified bases from the sugar component of DNA
An in vitro transcription system transcribes an Escherichia coli gene but transcription terminates inefficiently. Which component is likely missing from the in vitro system? A) Sigma factor B) Rho factor C) Mediator D) TATA-binding protein E) Release factor
B) Rho factor
Human birth weights have evolved over time to a medium weight of 7.5 pounds. This is due to the fact that extreme birth weights are often associated with higher instance of infant mortality; babies of low birth weight lose heat more quickly and get ill from infectious diseases more easily whereas babies of large body weight are more difficult to deliver through the pelvis. What mechanism of natural selection has allowed for the abundance of babies born around 7.5 pounds? A) Directional selection B) Stabilizing selection C) Disruptive selection D) Balanced polymorphism E) Negative frequency-dependent selection
B) Stabilizing selection
In the absence of tryptophan, what happens to the genes within the trp operon in Escherichia coli? A) The presence of tryptophan decreases cAMP which prevents CAP from binding to the CAP site, decreasing gene expression B) The inactive repressor cannot bind to the operator and the structural genes get transcribed C) Lack of tryptophan increases the level of cAMP high, which leads to activation of CAP protein and gene expression D) The active repressor binds to the operator and genes do not get transcribed E) None of the above; tryptophan does not have an affect on the expression of the operon
B) The inactive repressor cannot bind to the operator and the structural genes get transcribed
The Hardy-Weinberg equilibrium requires all of the following assumptions EXCEPT: A) Mating is random. B) The population is small. C) No selection is taking place. D) There is no immigration. E) Actually, it requires all of these assumptions.
B) The population is small.
In the fictional land of Westeros, beyond the Wall, the small population of individuals at Craster's keep is well known to engage in incestuous breeding over several generations. Based on this information, which of the following statements is TRUE? A) This population is an example of outbreeding B) This population is an example of positive assortative mating C) The overall Darwinian fitness of the population will increase over time D) All of the above statements are true E) None of the above statements are true
B) This population is an example of positive assortative mating
DNA ligase is needed in a cloning experiment for what reason? A) To proofread the vector for mistakes B) To covalently link the sugar-phosphate backbone of the DNA molecule C) To allow the vector to enter the cell D) It serves as a selectable marker E) To cut both the target molecule and the vector
B) To covalently link the sugar-phosphate backbone of the DNA molecule
Unmethylated cytosine is deaminated to form ________. The __________ system would be used to repair the mutated nucleotide. A) Thymine; direct repair B) Uracil; base excision repair C) Thymine; mismatch repair D) Uracil; non-homologous end joining repair E) Uracil; homologous recombination repair
B) Uracil; base excision repair
Which of the following describes the role of glucose in catabolite repression of the lac operon in Escherichia coli? A) When glucose levels are high, cAMP levels are high, allowing cAMP to bind to CAP and activate transcription of the lac operon B) When glucose levels are low, cAMP levels are high, allowing cAMP to bind to CAP and activate transcription of the lac operon C) When glucose levels are high, cAMP levels are high, allowing cAMP to bind to the lac repressor and decrease transcription of the lac operon D) When glucose levels are low, cAMP levels are high, allowing cAMP to bind to the lac repressor and decrease transcription of the lac operon E) None of the above, glucose does not play a role in catabolite repression in the lac operon of E. coli
B) When glucose levels are low, cAMP levels are high, allowing cAMP to bind to CAP and activate transcription of the lac operon
Which of the following is a type of RNA that gets translated? A) rRNA B) mRNA C) tRNA D) miRNA E) A, B, and C all get translated
B) mRNA
If there are two alleles, A and a, in a population and the population is at Hardy-Weinberg equilibrium, which frequency of A would produce the greatest frequency of heterozygotes? A) 0.1 B) 0.25 C) 0.5 D) 0.75 E) All of the above would have the same frequency of heterozygotes
C) 0.5
You have discovered a gene from a new bacterium Kingus midas that enables organisms to accumulate gold by concentrating trace amounts found in normal soil. You want to introduce this gene into Agrobacterium tumefaciens, a soil bacterium, using a Ti plasmid that has an ampicillin resistance selectable marker. List the order of steps (left to right) that would be needed to accomplish this task. (Note: not all steps for cloning may be shown below). 1. Transform the Ti plasmid into Agrobacterium tumefaciens 2. Amplify the gold gene from Kingus midas using polymerase chain reaction (PCR) 3. Identify bacterial cells that have the recombinant plasmid by plating the cells on growth media containing ampicillin 4. Digest both the gold gene from Kingus midas and the Ti plasmid with the same, appropriate restriction enzyme A) 1, 2, 3, 4 B) 2, 3, 1, 4 C) 2, 4, 1, 3 D) 2, 4, 3, 1 E) 4, 2, 1, 3
C) 2, 4, 1, 3
Tay-Sachs disease is caused by loss-of-function mutations in a gene on chromosome 15 that encodes a lysosomal enzyme. Tay-Sachs is inherited as an autosomal recessive condition. Among Ashkenazi Jews of Central European ancestry, about 1 in 3600 children are born with the disease. What percentage of individuals in this population are carriers? A) 1.7% B) 98.3% C) 3.3% D) 0.03% E) 96.6%
C) 3.3%
Blue eyes are recessive to brown eyes in humans. If the frequency of blue-eyed individuals in a population is 16%, we can calculate that the frequency of the allele for blue eyes is: A) 16%. B) 32% C) 40% D) 48% E) None of the above.
C) 40%
Which of the following base changes in DNA is an example of a transition? A) A-to-C B) G-to-C C) A-to-G D) Both answer choices A and B are examples of a transition E) None of the above
C) A-to-G
The hemoglobin gene exists in two forms: the sickle cell anemia allele and the normal allele. The sickle cell anemia allele can lead to sickle cell anemia (if two copies are inherited), but it can also provide resistance to malaria for the Subsaharan African population where malaria is prevalent. The normal allele does not lead to sickle cell anemia, but it also does not provide protection against malaria. The prevalence of both the sickle-cell anemia allele and the normal allele in the Sub-Saharan African population is an example of which of the following? A) Negative frequency-dependent selection B) Disruptive selection C) Balancing selection D) Random genetic drift E) Directional selection
C) Balancing selection
The role of sigma factors in bacterial transcription is to: A) Instruct the RNA polymerase where to stop transcription B) Unwind the DNA to initiate transcription C) Bind the consensus sequences to identify the start site for transcription D) Provide the first nucleotide in the synthesized RNA molecule E) None of the above
C) Bind the consensus sequences to identify the start site for transcription
A eukaryotic transcription factor's function can be modulated by all of the following EXCEPT? A) Binding of a small effector molecule (such as a hormone) to the transcription factor B) Protein-protein interaction between the transcription factor and another protein C) Binding of RNA polymerase directly to the transcription factor D) Covalent modification (i.e. phosphorylation) of the transcription factor
C) Binding of RNA polymerase directly to the transcription factor
What is one difference between chorionic villus sampling and amniocentesis? A) Chorionic villus sampling can only be performed on newborns, whereas amniocentesis can be performed on a developing fetus B) Amniocentesis can be performed earlier in fetal development than chorionic villus sampling C) Chorionic villus sampling can provide same-day results, while amniocentesis results take several weeks D) Amniocentesis poses a slights greater risk of miscarriage than chorionic villus sampling E) Only chorionic villus sampling requires that fetal cells be grown in cell culture
C) Chorionic villus sampling can provide same-day results, while amniocentesis results take several weeks
Which of the following testing methods for genetic abnormalities can be used to determine differences in gene expression levels as a result of cancer? A) Karyotype B) In situ hybridization C) DNA microarray D) RFLP analysis E) Biochemical (enzymatic) assay
C) DNA microarray
How do germ-line mutations differ from somatic mutations? A) Germ-line mutations involve small changes to DNA such as base-pair substitutions, while somatic mutations usually involve large deletions B) Germ-line mutations occur during DNA replication, while somatic mutations do not C) Germ-line mutations result in mutant gametes, while somatic mutations do not D) Germ-line mutations only affect a portion of the individual while somatic cell mutations affect the whole individual E) All of the above are correct
C) Germ-line mutations result in mutant gametes, while somatic mutations do not
The tryptophan repressor in Escherichia coli undergoes a mutation within the coding sequence such that the 44th amino acid is changed from threonine to methionine, rendering the protein inactive. A second mutation within the coding sequence of the gene mutates the 18th amino acid from glutamic acid to lysine, allowing the protein to be functional again. The second mutation is best described as? A) Intergenic suppressor mutation B) Nonsense mutation C) Intragenic suppressor mutation D) Silent mutation E) Lethal mutation
C) Intragenic suppressor mutation
Embryonic stem cells can give rise to a variety of cell types, but not a whole individual. This type of stem cell is classified as? (Hint: Yamanaka won the 2012 Nobel Prize for the ability reprogram cells into this form). A) Unipotent B) Totipotent C) Pluripotent D) Multipotent E) Polypotent
C) Pluripotent
Ultraviolet light causes what type of DNA lesion? A) Large deletions B) Deaminated cytosines C) Pyrimidine (i.e. thymine) dimers D) Mismatch bases E) Depurinations
C) Pyrimidine (i.e. thymine) dimers
What is the most likely result from mutating the Shine-DelGarno sequence in a prokaryotic cell? A) The first amino acid in the protein would be changed B) Transcription would not initiate C) The ribosome would not be able to bind to the mRNA D) The transcribed mRNA would be less stable E) None of the above, Shine DelGarno sequences are not found in prokaryotes
C) The ribosome would not be able to bind to the mRNA
You are observing transcription rates of a eukaryotic gene. After removing a DNA sequence near the gene of interest, you notice that the rate of transcription drastically increases. Which of the following sequences have you most likely removed? A) The operator B) The enhancer C) The silencer D) The promoter E) Removing any of the above would increase gene expression
C) The silencer
In four o'clock plants, two alleles (R, r) produce three petal colors. RR plants have red petals, Rr plants have pink petals, and rr plants have white petals. There is a population of four o'clock plants in which there are 40 plants with red petals, 50 plants with pink petals, and 10 plants with white petals. How many alleles total are there within this population? A) 50 B) 2,000 C) 100 D) 200 E) Cannot be determined from the information provided
D) 200
Which of the following could account for Species X having a higher Darwinian fitness than Species Z? A) Species X is more likely than species Z to survive predation B) Species X is more likely than species Z to mate C) Species X is more fertile than species Z D) All of the above could account for the higher Darwinian fitness value E) None of the above could account for the higher Darwinian fitness value
D) All of the above could account for the higher Darwinian fitness value
You are studying the frequency of alleles for a polymorphic gene within a population of ground finches on the island Daphne Major. Which of the following conditions would lead to a change in allele frequencies for the population of ground finches on Daphne Major? A) Migration between ground finches on the island Daphne Major and the nearby island Daphne Minor B) Increased reproductive success of ground finches due to a mutation that increases survival C) An earthquake killing most of the individuals on Daphne Major D) All of the above would lead to a change in the allele frequencies of the ground finch population E) None of the above would lead to a change in the allele frequencies of the ground finch population
D) All of the above would lead to a change in the allele frequencies of the ground finch population
Spontaneous mutations fall into different categories that can include all of the following except? A) Tautomeric shift B) Depurination C) Deamination D) Intercalating agent E) All of the above are types of spontaneous mutations
D) Intercalating agent
Which of the following is typically found on the primary product of transcription (the pre-mRNA) but not on a mature mRNA molecule? A) Start codon B) Promoter C) Exons D) Introns E) Stop codon
D) Introns
In which of the following scenarios would transcription of the lac operon in Escherichia coli be the highest? A) Lactose absent, Glucose absent B) Lactose absent, Glucose present C) Lactose present, Glucose present D) Lactose present, Glucose absent E) All of the above conditions would have the same level of transcription of the lac operon
D) Lactose present, Glucose absent
Which of the following is not needed during polymerase chain reaction (PCR)? A) DNA polymerase (i.e. Taq DNApolymerase) B) Deoxyribonucleotide triphosphates (dNTPs) C) Oligonucleotide primers D) Restriction endonuclease E) Target DNA
D) Restriction endonuclease
Which of the following types of mutations does NOT lead to a change in the amino acid sequence of the gene product? A) Missense B) Nonsense C) Neutral D) Silent E) Loss-of-function
D) Silent
Gene flow is best described as? A) The movement of genetic material from the nucleus to the cytoplasm B) The transmission of genetic information from the parent to the offspring C) The movement of genes from one chromosome to another D) The transfer of alleles from one population to another based on migration between populations E) The movement of genetic material from one microorganisms to another via a pilus
D) The transfer of alleles from one population to another based on migration between populations
Which of the following would NOT indicate that a disease has a genetic basis? A) Similar disease is seen in a mouse model B) Disease develops at a particular age of onset C) Disease is more likely to occur in blood relatives than in the general population D) A correlation is observed between the disease and a mutant human gene E) Actually, all of the above show that this disease has a genetic basis
E) Actually, all of the above show that this disease has a genetic basis
Which of the following is/are trait(s) that have been modified in transgenic plants? A) Resistance to insects B) Resistance to herbicides C) Improvement in storage (i.e. shelf life) D) Production of vaccines E) All of the above
E) All of the above
Which of the following is/are cloning vector(s)? A) pBluescript (a plasmid that can replicate in Escherichia coli) B) Escherichia coli (a model bacterium) C) SV40 (a virus that naturally infects mammalian cell) D) HaeIII (a restriction enzyme) E) Both answer choices A and C are vectors
E) Both answer choices A and C are vectors
Before the London Industrial Revolution, peppered moths were primarily white. This coloration enabled them to blend in with the bark from light-colored trees in the city and protect themselves from predators. Some moths had dark coloration, but this phenotype was less frequent. Over the course of several generations, the London air became polluted, and the bark of many light colored trees became covered with dark soot. As a result, in the moth population, the darker phenotype became more abundant. This is an example of? A) Balancing selection B) Disruptive selection C) Negative frequency dependent selection D) Stabilizing selection E) Directional selection
E) Directional selection
Which of the following statements is/are TRUE regarding restriction endonucleases? A) They are derived from humans as a protective mechanism against bacteria B) They are enzymes that cut RNA C) When restriction enzymes cut their target sequence, they always generate blunt ends D) All of the above are true E) None of the above are true
E) None of the above are true
Which of the following is a form of direct DNA repair? A) Base-excision repair B) Nucleotide excision repair C) Homologous recombination D) Mismatch repair E) Photoreactivation
E) Photoreactivation