Biology 1050 Exam 2

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1. Which of the following is TRUE about DNA?

a) All living organisms carry DNA in practically ever cell in their bodies.
b) DNA can serve as an "individual identifier."
c) DNA carries instructions for the functions of every cell and enzyme in living organisms.
d) DNA carries a record of evolutionary history.
e) All of the above are true.
e) All of the above are true.
Why has DNA analysis been effective recently at overturning faulty criminal convictions?

a) Genetic evidence can determine if an individual is predisposed to criminal behavior.
b) Scientific evidence was not admissible in U.S. courts until just recently.
c) DNA evidence is a more reliable individual identifier compared to eyewitness testimony.
d) Juries have tended to exhibit biases against DNA evidence in the past; however, that trend is now changing.
e) Scientists only discovered in 2005 that each individual's DNA is unique.
c) DNA evidence is a more reliable individual identifier compared to eyewitness testimony.
3. The Russian-American biochemist Phoebus Levene was the first to determine that nucleotides may contain one of four different nitrogen-containing bases. Levene believed that the nitrogen-containing bases occurred in equal amounts in DNA. What is the actual proportion of these bases?

a) All four do actually occur in equal amounts. Levene was right.
b) DNA contains equal amounts of adenine and guanine, and equal amounts of thymine and cytosine.
c) DNA contains equal amounts of guanine and thymine, and equal amounts of adenine and cytosine.
d) DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine.
e) DNA contains twice as much adenine and thymine as guanine and cytosine.
d) DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine.
4. Double-stranded DNA that contains a high G-C content requires a higher temperature in order to separate the two DNA strands. This is because:

a) high G-C content makes the DNA less flexible.
b) DNA with a high G-C content forms a tighter double helix.
c) G-C base pairing involves three hydrogen bonds, whereas A−T pairing involves only two.
d) All of the above are correct.
e) Only a and b are correct.
c) G-C base pairing involves three hydrogen bonds, whereas A−T pairing involves only two.
5. In any DNA molecule, the number of guanine bases will:

a) always be equal to the number of adenine bases.
b) always be equal to the number of thymine bases.
c) sometimes be equal to the number of cytosine bases and will sometimes be equal to the number of adenine bases.
d) sometimes be equal to the number of thymine bases and will sometimes be equal to the number of adenine bases.
e) always be equal to the number of cytosine bases.
e) always be equal to the number of cytosine bases.
6. DNA is a macromolecule that stores information. Which component of the DNA is the source of this information?

a) the phosphate group
b) the sugar
c) the base
d) the histone
e) the ladder
c) the base
. The human genome is composed of approximately how many base pairs?

a) 3 billion
b) 10 billion
c) 30 billion
d) 100 billion
e) 1 trillion
a) 3 billion
8. Alternate versions of a gene are called _______________. They can code for different ________________ of the same character.

a) alleles; traits
b) bases; chromosomes
c) bases; alleles
d) alleles; bases
e) chromosomes; traits
a) alleles; traits
The expression of a gene to form a polypeptide occurs in two major steps. What are these two steps in their correct chronological order?

a) transcription and then replication
b) translation and then transcription
c) transcription and then translation
d) replication and then translation
e) replication and then transcription
c) transcription and then translation
To get from a gene to a protein, two processes must occur: transcription, in which a copy of ______________, and translation, in which that copy is used to direct the production of a(n) _______________.

a) a protein's sequence of bases is made; amino acid
b) the gene's sequence of bases is made; genome
c) the gene's sequence of bases is made; protein
d) a protein's sequence of amino acids is made; gene
e) the gene's sequence of bases is made; amino acid
c) the gene's sequence of bases is made; protein
From DNA to protein involves which series of events?

a) transcription, translation
b) reverse-transcription, translation
c) translation, transcription
d) transduction, translation
e) translocation, transcription
a) transcription, translation
Transcription is like copying a recipe onto a notecard, EXCEPT:

a) you write all the letters upside down.
b) the copy is made in code.
c) you have to copy using your left hand (unless you're left-handed, then you have to copy using your right hand).
d) the notecard is black and the letters are white.
e) None of the above is correct; transcription is just like copying a recipe onto a notecard.
b) the copy is made in code.
A given section of DNA with the sequence AATGGCTAT is transcribed. What is the corresponding sequence on the mRNA transcription?

a) UUACCGAUA
b) UUGAACGUA
c) GGTAACTGT
d) TTACCGATA
e) CCGTTAGCT
a) UUACCGAUA
During transcription, at the point where the DNA strand being copied has an adenine, a(n)_______________ is added to the mRNA.

a) uracil
b) tRNA
c) adenine
d) cytosine
e) thymine
a) uracil
One of the four nucleotide bases in DNA is replaced by a different base in RNA. Which base is it, and what is it replaced by?

a) thymine, replaced by uracil
b) guanine, replaced by cytosine
c) adenine, replaced by uracil
d) thymine, replaced by guanine
e) cytosine, replaced by guanine
a) thymine, replaced by uracil
Which of the following is the primary site of protein assembly within eukaryotic cells?

a) the smooth endoplasmic reticulum
b) the ribosomes
c) the peroxisome
d) the Golgi apparatus
e) the vesicles
b) the ribosomes
Which of the following can be said about a frameshift mutation?

a) It must involve the insertion or deletion of nucleotides.
b) It changes the reading frame of the protein coding sequence.
c) It usually doesn't change the amino acid sequence very drastically.
d) Only a and b are correct.
e) None of the above is correct
d) Only a and b are correct.

a) It must involve the insertion or deletion of nucleotides.
b) It changes the reading frame of the protein coding sequence.
Mutation rates:

a) are generally unimportant in evolution.
b) can be affected by environmental factors.
c) are equal in all species—this is why we can accurately calibrate a molecular clock.
d) tend to be higher in E. coli than in Homo sapiens.
e) can be synonymous or non-synonymous
b) can be affected by environmental factors.
If the probability of a point mutation in a species were 10−8 per base pair per generation and each gamete in that species contained 3 10−8 base pairs, how many new point mutations would you expect per gamete per generation?

a) 10−8
b) 3 × 10−8
c) 3
d) 6
e) 1
c) 3
After amplifying one gene of interest using PCR (polymerase chain reaction), you pour your DNA sample into a gel to ensure that the reaction worked. To your surprise, two bands are present on the gel instead of a single band. What is a likely explanation for this outcome?

a) Two alleles exist for the gene and they vary in size.
b) The gene is co-dominant.
c) The gene contains a mutation.
d) The DNA sample was derived from a diploid individual.
e) The DNA sample was derived from a haploid individual
a) Two alleles exist for the gene and they vary in size.
Bacteria use restriction enzymes to:

a) destroy foreign protein.
b) synthesize protein.
c) synthesize RNA.
d) destroy foreign DNA.
e) synthesize DNA.
d) destroy foreign DNA
Which of the following is a symptom of vitamin A deficiency?

a) blindness
b) blood doping
c) severe combined immunodeficiency disease (SCID)
d) anemia
e) diabetes
a) blindness
22. Tomato plants that have pest-resistance genes inserted into the genome can be called:

a) cloned organisms.
b) genetically engineered organisms.
c) transgenic organisms.
d) Only b and c are correct.
e) All of the above are correct.
d) Only b and c are correct.
Bt corn is a genetically engineered plant. What feature gives it value as a crop plant?

a) The plant grows significantly larger ears of corn.
b) The plant produces better tasting fruits.
c) The plant produces a toxin designed to kill corn borers.
d) The plant produces a toxin designed to kill monarch butterflies.
e) The plant produces a toxin designed to kill competing plants (also known as weeds).
c) The plant produces a toxin designed to kill corn borers.
The loss of genetic diversity in crop plants can become disastrous. The Irish Potato Famine is an example of this problem. Which of the following is NOT a correct statement about the Irish Potato Famine?

a) Most of the potatoes in Ireland were propagated from cuttings of the same plant.
b) In the mid-1800s, much of the population of Ireland depended on potatoes.
c) The potato originated in Ireland.
d) When the crops were infected by a rot-causing mold, all of the potato plants were susceptible and most were wiped out.
e) Most of the potatoes in Ireland were genetically the same.
c) The potato originated in Ireland.
Transgenic bacteria are bacteria:

a) that have a sequence of DNA from another organism inserted into them.
b) that only have trans-DNA.
c) that have hybridized with other species of bacteria.
d) found in the DNA of other organisms.
e) that produce genes used in recombinant DNA technology.
a) that have a sequence of DNA from another organism inserted into them.
26. Diabetes is a chronic disease in which the body cannot produce ________________, a chemical that allows cells to take up and break down sugar from the blood.

a) insulin
b) erythropoietin
c) human growth hormone
d) polysaccharide
e) aldehyde dehydrogenase
a) insulin
Gene therapy involves:

a) the replacement of organs from patients with genetic disorders by transplantation.
b) drug treatment of patients with genetic disorders at specific times that correspond with cell division.
c) no controversial or ethical questions.
d) introducing non-defective genes into the cells of an individual with a genetic disorder.
e) All of the above are correct
d) introducing non-defective genes into the cells of an individual with a genetic disorder.
Which of the following is TRUE about cloning?

a) Cloning specifically refers to creation of new individuals with the exact genome as a donor individual.
b) Hans Spemann successfully cloned the first animal in 1938.
c) The only successfully cloned animals have been sheep.
d) Cloning refers to a variety of techniques, ranging from whole organism cloning to tissue and organ cloning.
e) Scientists have successfully cloned a dinosaur from DNA fragments found in preserved fossils.
d) Cloning refers to a variety of techniques, ranging from whole organism cloning to tissue and organ cloning.
You are cloning a sheep. You have just implanted the nucleus from a mammary cell from one sheep into an egg cell from another. What is the next step?

a) inducing cell division
b) isolating an egg cell from one sheep and a mammary cell from another
c) growing the embryo in culture
d) transplanting the embryo into the uterus of a surrogate mother sheep
e) removing the nucleus from the mammary cell
a) inducing cell division
Which of the following is NOT an example of a possible agricultural application for animal cloning?

a) cloning cows that produce more milk
b) cloning chickens that lay more eggs
c) cloning sheep that produce more wool at a younger age
d) cloning turkeys that have larger breast muscles
e) cloning hamsters to produce human erythropoietin (EPO).
e) cloning hamsters to produce human erythropoietin (EPO).
31. In order for a person's DNA to be used for his/her identification, which of the following tools/techniques must also be used in the process?

a) PCR
b) gel electrophoresis
c) restriction enzymes
d) All of the above techniques/tools must be used.
e) Only b and c must be used.
d) All of the above techniques/tools must be used.

a) PCR
b) gel electrophoresis
c) restriction enzymes
Microsatellites are short sequences of DNA that consist of several two- or three- nucleotide motifs repeated in tandem (e.g., AATAATAAT or GAGAGAGAGAGA). Each allele consists of a different number of repeats. Microsatellites are typically not under selection, and they are inherited through Mendelian inheritance. Given this information, which of the following questions might you answer with the use of microsatellites?

a) whether two puppies were sired by the same father
b) whether a gene is dominant or recessive
c) whether your child will be blonde- or brown-haired
d) whether a human fetus is male or female
e) whether your canary died of a viral or bacterial infection
a) whether two puppies were sired by the same father
All human DNA is nearly identical. Only about ____ of the DNA sequences of two people will differ. Even so, this difference still translates to roughly ______ base-pair differences.

a) 0.1%; 100
b) 0.1%; 1 million
c) 0.1%; 3 million
d) 1%; 3 million
e) 1%; 10 million
c) 0.1%; 3 million
Define these terms and describe the relationship among them: gene, chromosome, genome.
A gene is a specific sequence of DNA that contains the information necessary to produce all or part of a protein molecule. A chromosome is one or more unique pieces of DNA that make up an organism's genome. A genome is an organism's complete set of DNA. The relationship among these three terms is that the genome consists of chromosomes and individual genes are found on those chromosomes
Is the size of an organism's genome a clear indicator of its complexity? Why or why not?
There actually does not seem to be any relationship between the size of an organism's genome and its complexity! In humans, genes only make up about 2% of the DNA. A huge proportion of the base sequences in DNA do not code for proteins and have no known purpose; these are known as "non-coding" DNA. Some of this DNA is important in DNA regulation or may have a protective function
What is a mutation? What are the three ways mutations arise?
A mutation is an alteration in the sequences of bases in an organism's DNA. The three types of mutations are: spontaneous mutations, radiation-induced mutations, and chemical-induced mutations.
What is Bt corn? How has it led to reduced pesticide use by farmers?
Bt corn is corn engineered to contain spores of the bacterium Bacillus thuringiensis, a bacterium that kills insect pests, such as caterpillars, but does not harm humans. Bt crystals are produced by the engineered corn plant and are present in all of the plant's cells. Because Bt crystals are toxic to pests, farmers are able to reduce the amount of chemical pesticides they use.
Has gene therapy been successful? Why or why not?
More than 500 clinical trials for gene therapies have been conducted. These trials were designed to treat or cure a variety of diseases by inserting a functional gene into an individual's cells to replace a defective version of the gene; however, no clear successes have been achieved. This lack of success is due to a few known difficulties: difficulty getting the working gene into the specific cells where it is needed; difficulty getting the working gene into enough cells and at the correct rate to produce a physiological effect; difficulty arising from the transfer organism; and difficulty regulating gene expression.
What is a "DNA fingerprint"?
Short tandem repeats, or STRs, are sequences of DNA (four or five nucleotides) that repeat over and over again, occurring in some of the most highly variable regions of an individual's DNA. These STRs allow for a DNA fingerprint to be obtained by looking at the 13 different STR locations in an individual. For a single STR region, two numbers reflecting the number of STR repeats in the copies inherited from the mother and the father express an individual's genotype. The DNA fingerprint essentially is a string of 26 numbers that includes the 2 numbers for each of 13 STRs.
How similar are two people with respect to chromosomes, genes, and alleles?
Two people have the same number of chromosomes (46 for humans), and have the same genes arranged on these chromosomes; however, they have different alleles of many of these genes.
In a few sentences, summarize the four steps of transcription, in which an mRNA copy of a gene is produced.
The enzyme RNA polymerase binds to the promoter region at the beginning of a gene, after which it proceeds to assemble RNA nucleotides in an order dictated by the DNA sequence of the gene. This synthesis continues until the enzyme encounters a termination sequence at the end of the gene and detaches from the DNA. The newly synthesized mRNA molecule is then modified before being transported to the cytoplasm
Describe the three ways in which an initial mRNA molecule is modified before transport to the cytoplasm.
The initial RNA transcript is modified in three ways. Extra pieces of non-coding RNA (introns) that are within the gene are snipped out. Also, a cap is added to the beginning of the molecule, and a tail is added to the end of the molecule. Both of these additions protect the transcript and assist with the next process: translation.
Where does transcription take place in a eukaryotic cell? How about RNA editing? How about translation?
Answer: Both transcription and RNA editing occur in the nucleus of a eukaryotic cell, whereas translation occurs in the cytoplasm.
Both transcription and RNA editing occur in the nucleus of a eukaryotic cell, whereas translation occurs in the cytoplasm.
In approximately three sentences, summarize the three steps in translation, in which a protein is assembled as directed by the information in an mRNA molecule.
The subunits of a ribosome assemble around the start sequence (AUG) on an mRNA molecule. tRNA molecules connected to amino acids bind to codons on the mRNA molecule, and these amino acids are connected into a growing chain by the ribosome. The ribosome finally encounters the stop sequence, which signals the end of translation. During this process, the chain of amino acids folds up into the three-dimensional structure of the functional protein.
Are mutations helpful, harmful, or both? Explain.
Some mutations are helpful and some are harmful. Because more mutations are harmful than are helpful, mutations can be considered to be generally harmful at the level of the individual; however, mutations provide the raw material for evolutionary change and are very important in populations.