Biology chapter 6
What percentage of our genome actually accounts for all the differences we observe among members of the human genome?
.5%
How many more nucleotides does the human genome have when compared to the chimpanzee?
100 million
If thymine makes up 20% of the bases in a DNA double helix, what percentage of the bases is guanine?
30%
How many genes does rice have in its genome? Does it seem that there is a relationship between the complexity of an organism and the number of genes in its genome? Briefly explain your answer.
42,000. No, there is no relationship between the number of genes in an organism's genome and its complexity, because rice has twice as many genes as us and most people would consider rice to be less complex than humans.
Place the following events of signal transduction in order: activated protein travels inside the nucleus; a new protein is made; a cell sends a signal molecule; a couple of cytoplasmic proteins relay the message; a receptor in the cell's membrane binds the signal molecule; a gene is turned on.
A cell sends a signal molecule, a receptor in the cell's membrane binds the signal molecule, a couple of cytoplasmic proteins relay the message, activated protein travels inside the nucleus, a gene is turned on, and a new protein is made.
Sometimes humans are born with some of their fingers or toes fused together. This condition is known as syndactyly. What is a possible explanation for this occurrence?
A possible explanation for this is that induction failed to occur properly.
If three DNA bases of the template strand are AGT, what is the anticodon of the tRNA that brings the amino acid?
AGU
STR analysis relies on A) thirteen sites within the human genome. B) an STR of four nucleotides repeated from 3 to 50 times. C) PCR to increase the DNA at the STR sites. D) all of the above.
All of the above
Scientists have been able to do which of the following as a result of manipulating DNA? A) Create genetically modified organisms B) Identify disease-causing genes C) Create artificial life forms D) All of the above
All of the above
Suppose that a mistake during DNA replication results in the mRNA below being changed to have an A at position number 6 instead of a G (AUGUGGAAUCCACUGUGA-> AUGUGAAAUCCACUGUGA). This A) is considered a mutation. B) changes at least one of the amino acids. C) results in a polypeptide that is shorter than it should be. D) results in all of the above.
All of the above
Which of the following RNA molecules is involved in the process of translation? A) mRNA B) rRNA C) tRNA D) All of the above
All of the above
Propose an explanation for how the human genome contains only 21,000 genes but ultimately codes for 100,000 proteins
Alternate gene splicing during RNA splicing after transcription would account for this situation.
A scientist begins a PCR with 10 picograms of DNA and allows it to go through three cycles. How much DNA, in picograms, does the scientist have at the end of three cycles?
At the end of three cycles the scientist has 80 picograms of DNA.
The inactive X chromosome in a human female cell condenses into what structure?
Barr body
List three examples of genetically modified crops.
Bt corn, golden rice, and ring spot resistant papaya
Cancer usually takes a while to develop. People have multiple proto oncogenes with overlapping areas of control over cell division. Use these two pieces of information to propose an explanation about why cancer takes a while to develop.
Cancer usually takes a while to develop because it takes time to accumulate mutations in enough proto oncogenes in order for the cell to lose control over cell division.
What basic principle makes a nucleic acid probe possible?
Complementary base pairing
The molecule of heredity is
DNA
Correct the following: RNA-> protein-> DNA
DNA --->RNA---> Protein
A scientist uses techniques that allow her to determine that a person left DNA at a crime scene. The scientist used
DNA profiling
The process by which a molecule of DNA is copied is known
DNA replication
Two types of nucleic acids that are found in all cells are ___ and ___.
DNA, RNA
Place the following steps of DNA replication in the proper order: DNA fragments are fused together; double helix is pulled apart; new strands of DNA are synthesized.
Double helix is pulled apart, new strands of DNA are synthesized, and DNA fragments are fused together
What codon does every mRNA molecule have in common? What amino acid begins every polypeptide?
Every mRNA molecule will have AUG (the start codon). Every amino acid will begin with methionine.
True or false: DNA profiling relies on matching entire genomes. If false, make it a true statement
False, DNA profiling relies on matching only small sequences.
True or false: A tumor is a group of cells in which cell division is still controlled. If false, make it a true statement.
False, a tumor is a group of cells in which cell division is no longer controlled.
True or false: DNA is directly responsible for producing your characteristics. If false, make it a true statement.
False, proteins are directly responsible for producing your characteristics, whereas DNA contains the information to make those proteins.
True or false: Scientists have not manipulated DNA due to moral and ethical concerns. If false, make it a true statement.
False, scientists have been manipulating DNA for some time.
True or false: The first organism to have its genome sequenced was Staphylococcus aureus. If false, make it a true statement.
False, the first organism to have its genome sequenced was Haemophilus influenzae.
True or false: The terminator is the sequence of DNA in front of the gene that tells the RNA polymerase where to begin transcription. If false, make it a correct statement.
False, the terminator is the sequence of DNA at the end of the gene that tells the RNA polymerase to stop transcription.
True or false: The process of translation occurs within the cytoplasm on a cellular structure known as the mitochondrion. If false, make it a true statement.
False, translation occurs on a ribosome.
True or false: Nucleic acids store the information to make carbohydrates. If false, make it a true statement.
False; nucleic acids contain the information to make polypeptides.
What role does heating and cooling play in PCR?
Heating the DNA allows the double helix to be unwound. Cooling allows the double helix to reform.
Certain viruses, like HIV, actually contain RNA. When a virus of this type takes over a host cell, it makes DNA from its RNA. The viral DNA is then used to make an RNA copy, which is used to make viral proteins. In all cells, the flow of genetic information is from DNA à RNA à proteins. Explain how this differs from viruses (which are not considered cells) like HIV.
In a virus like HIV, the virus will make DNA from its RNA and then proceed through a path familiar to our own (DNA à RNA à Protein). Specifically, it is the addition of that extra step at the beginning, which makes it different.
Place the following steps of translation in order: elongation, termination, and initiation.
Initiation, elongation, and termination
Are introns and exons found in DNA or RNA?
Introns and exons are found in RNA.
Place the following steps of gene therapy into the proper order: make an RNA copy of the gene; isolate the target gene from a healthy person; convert the normal RNA into DNA by the virus; inject the genetically modified cell back into the patient; put the RNA copy of the gene into a retrovirus; remove a cell from the patient; the normal DNA now inserts itself into the genome; the retrovirus infects the patient cell.
Isolate the target gene from a healthy person, make an RNA copy of the gene, put the RNA copy of the gene into a retrovirus, the retrovirus infects the patient cell, convert the normal RNA into DNA by the virus, the normal DNA now inserts itself into the genome, inject the genetically modified cell back into the patient, remove a cell from the patient
Describe the cancer treatment regimen of "slash, burn, and poison."
It involves surgery (slash), radiation (burn), and chemotherapy (poison).
You are a genetic researcher who studies development in fruit flies. One day you notice a fly that has the head and abdomen sections switched. You eventually identify the gene and its mutation that was responsible. What kind of gene was this? Briefly explain your answer.
It was likely a mutation in a homeotic gene because those genes tend to be involved in overall structural patterning of the organism.
A drug that changes the AUG codon to UAC would most likely have what effect on translation? Be brief but specific in your answer.
It would have a definite negative impact because the drug has changed the start codon.
Would X chromosome inactivation occur in human males? Briefly explain your answer either way.
No, X chromosome inactivation cannot occur in males because males have only one X chromosome.
Would gene therapy be an effective treatment for a non-genetic disease, like a staph infection caused by Methicilin-resistant Staphylococcus aureus (MRSA)?
No, gene therapy would not be effective because gene therapy only solves situations caused by inheritance of a faulty gene.
A student is given a sequence of DNA as follows: AACTAGCTAGCT, and is asked to provide the mRNA copy that would be made from that sequence during transcription. The student provides the following sequence: TTGATCGATCGA. Is this the correct sequence? If not, explain why it is incorrect and fix it.
No, it is not correct; the student gave the complementary DNA sequence. The correct sequence would be UUGAUCGAUCGA.
Are the two individuals shown here a match for the number of repeats at the STR site
No, one has 4 and one has 3.
List four methods of cancer prevention.
Not smoking, a healthy diet, sunscreen, and exercise
A brand new graduate student in biology is running a PCR experiment. After the PCR is running on the thermal cycler, he realizes that he forgot to add the free nucleotides. Briefly explain what the result will be.
Nothing will happen because there are no nucleotides from which to synthesize the new DNA.
Which of the following is used to construct a molecule of DNA?
Nucleotides
Place the following steps to the shotgun sequencing method in order: DNA sequencing, computer alignment of overlapping sequences, obtain DNA, upload the DNA into a database, cut the DNA with restriction enzymes.
Obtain DNA, cut the DNA with restriction enzymes, DNA sequencing, computer alignment of overlapping sequences, and upload the DNA into a database.
A method for quickly increasing the number of copies of a piece of DNA is called
PCR (polymerase chain reaction).
You are a biochemist and have been given a test tube containing a small amount of nucleic acid. You have been asked to determine whether it is DNA or RNA. Which of the following would be a characteristic that indicates RNA?
Presence of uracil, but no thymine Presence of ribose, but no deoxyribose
Why does a scientist not simply replace a defective protein with a normal protein? Why must a cell's genes be replaced?
Proteins have a finite lifetime and you would need to replace the gene in order to have a continuous supply of functional proteins.
List the following steps of transcription in order: RNA polymerase makes RNA; mRNA leaves the nucleus; RNA polymerase binds the promoter; RNA splicing
RNA polymerase binds the promoter, RNA polymerase makes RNA, RNA splicing, and mRNA leaves the nucleus
Translation converts the information stored in ____ into ______.
RNA; a protein
___________ ___________ can make DNA from RNA.
Reverse transcriptase
The use of the retrovirus is important because retroviruses contain an enzyme called reverse transcriptase. What
Reverse transcriptase is important because it is able to make DNA from RNA.
A scientist cuts a large amount of DNA using a restriction enzyme that she believes will produce a range of DNA pieces that are relatively similar in size. Scientists can vary the density of the agar gels by varying the amount of agar in the gel. Would she want to make an agarose gel with a higher or lower amount of agarose in order to get the DNA bands to separate? A higher amount of agarose in the gel makes it stiffer. Briefly explain your answer.
She would want a higher concentration of agarose because it would allow for better separation of the similar sized bands.
If a strand of DNA has the sequence AAGCTC, transcription will result in which of the following?
Single RNA strand with the sequence UUCGAG
If one polynucleotide strand of DNA has ACTTGACTAGCTA as its sequence of bases, what would be the sequence of bases on the opposing strand?
TGAACTGATCGAT
A scientist isolates an mRNA from the cytoplasm of a cell. He then uses it to make a cDNA copy from it. How does the cDNA differ from the original DNA of the gene?
The cDNA will be the sequence of DNA minus the introns.
The following diagram uses colors to illustrate the replication of a chromosome. Use your knowledge of DNA replication to determine whether or not the illustration is accurate. If it is not accurate, briefly explain how to make it correct.
The diagram is not accurate because it suggests that after replication, you end with entirely new and original DNA molecules. In reality, the two new DNA molecules would consist of one original strand of DNA and one new strand of DNA.
Is the following diagram a nucleotide of DNA, RNA, or could it be either one? Briefly explain your answer.
The diagram would have to be a nucleotide of RNA because the sugar is ribose and the pictured base is uracil. Both of those are only found in RNA.
What is the relationship between a genome and a genomic library?
The genomic library was created from the genome.
A gene is a specific section of DNA that contains the instructions to make a protein. If all molecules of DNA contain a phosphate group, a deoxyribose, and a base, propose an explanation for how the information to make a protein is coded within the DNA molecule.
The information to make a polypeptide is coded within the sequence of the bases.
You are a molecular biologist studying a defective human protein that is known to be a cause of a rare cancer. You isolate the suspected protein from a person with this cancer and compare it to the same protein in a person without the cancer. You discover that the protein isolated from the cancer patient is slightly smaller in size when compared to the protein from the unaffected patient. Furthermore, you discover that the protein from the cancer patient differs in almost every amino acid starting after the twenty third amino acid. What is the likely explanation?
The likely explanation is that there was an insertion or deletion that resulted in a frameshift mutation. The frameshift mutation also resulted in a stop codon appearing sooner than it normally should have, and this resulted in a shorter polypeptide.
A drug that inhibits DNA ligase but not DNA polymerase is added to a cell. Explain how DNA replication would be affected as a result of this drug.
The new DNA fragments would not be fused together and the backbone of the DNA would be incomplete.
The sequences and locations of short tandem repeats (STRs) are identical from person to person. What actually varies?
The number of times the sequence repeats is what varies.
A person suffering from cystic fibrosis is enrolled in an experimental program where the defective gene that causes the disease is replaced with the normal human gene. Is this person a GMO, transgenic organism, or both? Briefly explain your answer
The person would be a GMO because the inserted gene is still a human gene.
Overall, a molecule of DNA has a negative charge. Which component of DNA gives it this charge?
The phosphate group gives DNA its negative charge.
You are a graduate student at the University of Iowa and working as a teaching assistant for a freshman introductory biology course. Two of your students have come to you with a question about the sequence of an mRNA transcribed from a gene. The original DNA sequence from which the mRNA was transcribed reads: TGACGATCGTA. The students were asked to provide the sequence of bases in the mRNA and came up with the following mRNA sequence: ACTGCTAGCAT. They are confused because their answer does not match the answer in the book. Briefly explain the very common mistake they made and what the correct sequence would be.
The students gave you the complementary DNA sequence and not the complementary RNA sequence. The correct sequence should be as follows: ACUGCUAGCAU
How many codons are in the following mRNA sequence? AUGGGGCAGGUAUGA
There are 5 codons in that sequence.
Use the information from question 11 to determine how many amino acids would be in the polypeptide produced from that mRNA.
There would be four amino acids in that polypeptide. The 5th one is a stop codon and does not code for an amino acid.
Control of gene expression is analogous to controlling a radio. Briefly explain why this is a good analogy.
This is a good analogy because the expression of a gene can be turned on or off. Additionally, if a gene is turned on, it can also be turned up or down.
Briefly explain why a molecule of tRNA makes a good translator during the process of translation.
This is because the tRNA molecule attaches to both the amino acid and the mRNA.
What is the point of creating strands of DNA with "sticky" ends?
This is done in order to insert a gene into a plasmid. If the ends of the cut gene match the cut plasmid, then the two pieces of DNA can be "pasted" together.
Diabetic humans inject themselves with human insulin. However, the human insulin is made by a bacterium called Escherichia coli (E. coli). This is a result of which method of DNA manipulation?
This result would come from genetic engineering.
List three ways in which mRNA is modified after transcription
Three modifications include: addition of a cap, addition of a tail, and RNA splicing.
_________ is the process by which information stored in DNA is copied into mRNA.
Transcription
True or false: Ribosomes are part of the cytoplasm. If false, make it a true statement.
True
A patient's oncologist tells him that the biopsy of his brain tumor shows cell markers that are found only on lung cells. What has most likely happened?
What has most likely happened is that the cancer has metastasized.
Is a transgenic organism a GMO? Briefly explain your answer.
Yes, a transgenic organism is a GMO because a transgenic organism has DNA from two different species, which can only occur through genetic modification.
Is a normal tumor-suppressor gene considered a proto oncogene? Briefly explain your answer.
Yes, because the loss of function in such a gene would lead to a failure to properly regulate the cell cycle.
It is safe to assume that identical twins will show the same results from an STR analysis. However, can you propose a mechanism that would explain differing results? Hint: Use information from a previous module in this chapter.
Yes, if a mutation occurred at an STR site, this would cause the STR site to vary.
The template strand is the DNA strand directly used by the RNA polymerase to make the RNA copy. You are given the following mRNA sequence: AUGCUGAUU. Are you able to determine the sequence of bases on the DNA strand that was not transcribed? Briefly explain your answer either way.
Yes, you can determine the sequence, because the mRNA sequence will be complementary to the template strand, which, in turn, will be complementary to the DNA strand that was not transcribed.
According to the table of the genetic code shown here, changing the second base of the codon
always changes the amino acid that is encoded.
If a cell has one or more proto oncogenes mutate into oncogenes, that cell has begun to develop into
cancer
Cell division is controlled through a mechanism known as
cell cycle control system.
A series of three nucleotides that specifies an amino acid is a(n)
codon
A set of three nucleotides that specifies an amino acid is called a(n)
codon
Translation takes place in the ______ on a _________.
cytoplasm; ribosome
Which of the following describes the process by which an animal grows from an embryo into an adult?
development
___________ is the process by which a gene is found and many copies of it are made by using organisms that reproduce quickly.
gene cloning
The mechanism by which cells turn on and off specific genes is known as
gene expression
Changing a person's genes to treat an illness is known as
gene therapy
An organism that has acquired one or more genes as a result of artificial methods is a(n
genetically modified organism
An organism's entire set of DNA is called its
genome
_________ is the study of an organism's genome and the interactions of the genes within it.
genomics
Briefly explain why you think "mRNA" is a good name for the RNA copy made from DNA.
mRNA is a good name because it contains the "message," or code, for how to make a protein, and transfers it from the nucleus to the ribosomes in the cytoplasm.
________ is any change in the DNA's nucleotide sequence.
mutation
DNA is attracted to the positive pole because ________ electrical charges attract.
opposite
Which of the following is found in all nucleotides?
phosphate group
A gene has a sequence of DNA in front of it that directs the RNA polymerase where to begin transcription. This sequence of DNA is the ______________________.
promoter
Which of the following RNA molecules is a component of ribosomes?
rRNA
Mutation to a stop codon _______.
results in a shorter polypeptide chain
_________ is a series of molecular relays that bring a message from outside the cell to the nucleus. This signal conveys a message that usually results in one or more genes being turned on or off.
signal transduction pathway
True or false: A cell that divides constantly has undergone transformation. If false, make it a true statement.
true
True or false: A mutation can be a single nucleotide or groups of them. If false, make it a true statement.
true
True or false: A scientist can insert recombinant plasmids into crops and create transgenic plants. If false, make it a true statement.
true
True or false: A teenage girl who begins smoking reduces her life expectancy by 14 years. If false, make it a true statement.
true
True or false: Cell-to-cell signaling plays a key role in how your cells perform critical functions within tissues and organs. If false, make it a true statement.
true
True or false: DNA must be precisely copied prior to being passed on to the next generation. If false, make it a true statement
true
True or false: Gel electrophoresis is the visualization of DNA using an applied electrical current. If false, make it a true statement.
true
True or false: Gene expression refers to making a finished protein from DNA. If false, make it a true statement.
true
True or false: If a criminal leaves behind even a single cell at the crime scene, a scientist can make many copies of specific DNA sequences from that cell. If false, make it a true statement.
true
True or false: Recombinant DNA contains DNA from at least two sources. If false, make it a true statement.
true
A method for quickly sequencing a genome is called the
whole-genome shotgun cloning method.