BIO CHAPTER 10

Question 1

1) Which of the following statements regarding viruses is false?
A) A virus is generally considered to be alive because it is cellular and can reproduce on its own.
B) The host cell provides most of the tools and raw materials for viral multiplication.
C) Once a person is infected with the herpesvirus, the virus remains permanently latent in the body.
D) Viruses can enter a host cell when the protein molecules on the outside of the virus fit into receptor molecules on the
outside of the cell.
E) Herpesviruses and the virus that causes AIDS can remain latent inside our cells for long periods of time.

Answer 1

A) A virus is generally considered to be alive because it is cellular and can reproduce on its own.

Question 2

2) Which of the following people conducted the experiments that demonstrated that DNA is the genetic material of bacteriophages? 
A) Watson and Crick 
B) Hershey and Chase 
C) Franklin 
D) Griffith 
E) Pauling

Answer 2

B) Hershey and Chase

Question 3

3) One type of virus that infects bacteria is called a 
A) phage. 
B) mage. 
C) rhinovirus. 
D) filovirus. 
E) coronavirus.

Answer 3

A) phage.

Question 4

4) When a T2 bacteriophage infects an Escherichia coli cell, which part of the phage enters the bacterial cytoplasm?
A) the whole phage
B) only the RNA
C) only the DNA
D) the protein “headpiece” and its enclosed nucleic acid
E) the tail fibers

Answer 4

C) only the DNA

Question 5

5) The way that genetic material of a bacteriophage enters a bacterium is most like the way that
A) a drug is injected with a hypodermic needle.
B) a person swallows a pill.
C) skin lotion is rubbed onto the hands.
D) sugar dissolves in water.
E) water soaks into a sponge.

Answer 5

A) a drug is injected with a hypodermic needle.

Question 6

6) The monomers of DNA and RNA are 
A) amino acids. 
B) monosaccharides. 
C) nucleotides. 
D) fatty acids. 
E) nucleic acids.

Answer 6

C) nucleotides.

Question 7

7) Which of the following statements regarding DNA is false?
A) DNA uses the sugar deoxyribose.
B) DNA uses the nitrogenous base uracil.
C) DNA is a nucleic acid.
D) One DNA molecule can include four different nucleotides in its structure.
E) DNA molecules have a sugar-phosphate backbone.

Answer 7

B) DNA uses the nitrogenous base uracil.

Question 8

8) Which of the following statements regarding RNA is false?
A) RNA uses the sugar dextrose.
B) RNA uses the nitrogenous base uracil.
C) RNA is a nucleic acid.
D) One RNA molecule can include four different nucleotides in its structure.
E) RNA molecules have a sugar-phosphate backbone.

Answer 8

A) RNA uses the sugar dextrose.

Question 9

9) Which of the following statements regarding the structure of DNA is false?
A) The DNA molecule has a uniform diameter.
B) In a DNA molecule, adenine bonds to thymine and guanine to cytosine.
C) The DNA molecule is in the form of a double helix.
D) Watson and Crick received a Nobel Prize for their description of the structure of DNA.
E) The sequence of nucleotides along the length of a DNA strand is restricted by the base-pairing rules.

Answer 9

E) The sequence of nucleotides along the length of a DNA strand is restricted by the base-pairing rules.

Question 10

10) How would the shape of a DNA molecule change if adenine paired with guanine and cytosine paired with thymine?
A) The DNA molecule would be longer.
B) The DNA molecule would be shorter.
C) The DNA molecule would be circular.
D) The DNA molecule would have regions where no base-pairing would occur.
E) The DNA molecule would have irregular widths along its length

Answer 10

E) The DNA molecule would have irregular widths along its length

Question 11

11) The shape of a DNA molecule is most like 
A) a set of railroad tracks. 
B) a diamond ring. 
C) a twisted rope ladder. 
D) a gold necklace. 
E) the letter X.

Answer 11

C) a twisted rope ladder.

Question 12

12) Which of the following statements regarding a DNA double helix is always true?
A) The amount of adenine is equal to the amount of uracil, and the amount of guanine is equal to the amount of cytosine.
B) The amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of uracil.
C) The amount of adenine is equal to the amount of guanine, and the amount of thymine is equal to the amount of
cytosine.
D) The amount of adenine is equal to the amount of cytosine, and the amount of guanine is equal to the amount of
thymine.
E) The amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of
cytosine.

Answer 12

E) The amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of
cytosine.

Question 13

13) DNA replication
A) occurs through the addition of nucleotides to the end of the DNA molecule.
B) results in the formation of four new DNA strands.
C) produces two daughter DNA molecules that are complementary to each other.
D) uses each strand of a DNA molecule as a template for the creation of a new strand.
E) begins when two DNA molecules join together to exchange segments.

Answer 13

D) uses each strand of a DNA molecule as a template for the creation of a new strand.

Question 14

14) If one strand of DNA is CGGTAC, the corresponding strand would be 
A) GCCTAG. 
B) CGGTAC. 
C) GCCAUC. 
D) TAACGT. 
E) GCCATG.

Answer 14

E) GCCATG.

Question 15

15) The copying mechanism of DNA is most like
A) using a photographic negative to make a positive image.
B) mixing flour, sugar, and water to make bread dough.
C) joining together links to make a chain.
D) carving a figure out of wood.
E) threading beads onto a string.

Answer 15

A) using a photographic negative to make a positive image.

Question 16

16) When one DNA molecule is copied to make two DNA molecules, the new DNA contains 
A) none of the parent DNA. 
B) 25% of the parent DNA. 
C) 50% of the parent DNA. 
D) 75% of the parent DNA. 
E) 100% of the parent DNA

Answer 16

C) 50% of the parent DNA.

Question 17

17) Multiple origins of replication on the DNA molecules of eukaryotic cells serve to
A) remove errors in DNA replication.
B) create multiple copies of the DNA molecule at the same time.
C) shorten the time necessary for DNA replication.
D) reduce the number of “bubbles” that occur in the DNA molecule during replication.
E) assure the correct orientation of the two strands in the newly growing double helix.

Answer 17

C) shorten the time necessary for DNA replication.

Question 18

Which of the following enzymes catalyzes the elongation of a new DNA strand? 
A) helicase 
B) primase 
C) ligase 
D) single-stranded binding protein 
E) DNA polymerase

Answer 18

E) DNA polymerase

Question 19

Why does a DNA strand grow only in the 5’ to 3’ direction?
A) because DNA polymerases can only add nucleotides to the 3’ end of the growing molecule
B) because DNA polymerases can only add nucleotides to the 5’ end of the growing molecule
C) because mRNA can only read a DNA molecule in the 5’ to 3’ direction
D) because the DNA molecule only unwinds in the 5’ to 3’ direction
E) because DNA polymerase requires the addition of a starter nucleotide at the 5’ end

Answer 19

A) because DNA polymerases can only add nucleotides to the 3’ end of the growing molecule

Question 20

Which of the following options best depicts the flow of information when a gene directs the synthesis of a cellular component? 
A) RNA → DNA → RNA → protein 
B) DNA → RNA → protein 
C) protein → RNA → DNA 
D) DNA → amino acid → RNA → protein 
E) DNA → tRNA → mRNA → protein

Answer 20

B) DNA → RNA → protein

Question 21

The transfer of genetic information from DNA to RNA is called 
A) translation. 
B) transcription. 
C) initiation. 
D) elongation. 
E) promotion.

Answer 21

B) transcription.

Question 22

The “one gene-one polypeptide” theory states that
A) the synthesis of each gene is catalyzed by one specific enzyme.
B) the synthesis of each enzyme is catalyzed by one specific gene.
C) the function of an individual gene is to dictate the production of a specific polypeptide.
D) each polypeptide catalyzes a specific reaction.
E) the function of each polypeptide is to regulate the synthesis of each corresponding gene.

Answer 22

C) the function of an individual gene is to dictate the production of a specific polypeptide.

Question 23

Experiments have demonstrated that the “words” of the genetic code (the units that specify amino acids) are
A) single nucleotides.
B) two-nucleotide sequences.
C) three-nucleotide sequences.
D) nucleotide sequences of various lengths.
E) enzymes.

Answer 23

C) three-nucleotide sequences.

Question 24

The directions for each amino acid in a polypeptide are indicated by a codon that consists of \_\_\_\_\_\_\_\_ nucleotide(s) in an RNA molecule. 
A) 5 
B) 4 
C) 3 
D) 2 
E) 1

Answer 24

C) 3

Question 25

We would expect that a 15-nucleotide sequence will direct the production of a polypeptide that consists of 
A) 2 amino acids. 
B) 3 amino acids. 
C) 4 amino acids. 
D) 5 amino acids. 
E) 6 amino acids.

Answer 25

C) 4 amino acids.

Question 26

A base substitution mutation in a gene does not always result in a different protein. Which of the following factors could account for this?
A) the fact that the mutation affects only the sequence of the protein’s amino acids, so the protein stays the same
B) the double-ring structure of adenine and guanine
C) a correcting mechanism that is part of the mRNA molecule
D) the fact that such mutations are usually accompanied by a complementary deletion
E) the fact that some amino acids are specified from more than one codon

Answer 26

E) the fact that some amino acids are specified from more than one codon

Question 27

Which of the following enzymes catalyzes the linking together of RNA nucleotides to form RNA? 
A) RNA polymerase 
B) RNA ligase 
C) a ribozyme 
D) reverse transcriptase 
E) tRNA

Answer 27

A) RNA polymerase

Question 28

Which of the following occurs when RNA polymerase attaches to the promoter DNA?
A) elongation of the growing RNA molecule
B) termination of the RNA molecule
C) addition of nucleotides to the DNA template
D) initiation of a new RNA molecule
E) initiation of a new polypeptide chain

Answer 28

D) initiation of a new RNA molecule

Question 29

\_\_\_\_\_\_\_\_ marks the end of a gene and causes transcription to stop. 
A) RNA polymerase 
B) RNA ligase 
C) A terminator 
D) Reverse transcriptase 
E) Methionine

Answer 29

C) A terminator

Question 30

Where do transcription and translation occur in prokaryotic cells? 
A) on the plasma membrane 
B) in the nucleus 
C) in the cytoplasm 
D) in chromatophores 
E) in the cell wall

Answer 30

C) in the cytoplasm

Question 31

Which of the following statements about eukaryotic RNA is true?
A) Introns are added to the RNA.
B) Exons are spliced together.
C) A small cap of extra nucleotides is added to both ends of the RNA.
D) A long tail of extra nucleotides is removed from the 5’ end of the RNA.
E) The modified RNA molecule is transported into the nucleus.

Answer 31

B) Exons are spliced together.

Question 32

Which of the following takes place during translation?
A) the conversion of genetic information from the language of nucleic acids to the language of proteins
B) the conversion of genetic information from DNA nucleotides into RNA nucleotides
C) the addition of nucleotides to a DNA template
D) the conversion of genetic information from the language of proteins to the language of enzymes
E) DNA replication

Answer 32

A) the conversion of genetic information from the language of nucleic acids to the language of proteins

Question 33

Which of the following is a function of tRNA?
A) joining to several types of amino acid
B) recognizing the appropriate anticodons in mRNA
C) transferring nucleotides to rRNA
D) helping to translate codons into nucleic acids
E) joining to only one specific type of amino acid

Answer 33

E) joining to only one specific type of amino acid

Question 34

Which of the following is not needed in order for translation to occur?
A) DNA template
B) ribosomes
C) tRNA
D) various enzymes and protein “factors”
E) sources of energy, including ATP

Answer 34

A) DNA template

Question 35

Which of the following statements about ribosomes is false?
A) A ribosome consists of two subunits.
B) Subunits of RNA are made of proteins and ribosomal RNA.
C) The ribosomes of prokaryotes and eukaryotes are the same in structure and function.
D) Each ribosome has two binding sites for tRNA.
E) Ribosomes coordinate the functioning of mRNA and tRNA.

Answer 35

C) The ribosomes of prokaryotes and eukaryotes are the same in structure and function.

Question 36

Which of the following statements is false?
A) Translation consists of initiation, elongation, and termination.
B) During polypeptide initiation, an mRNA, the first amino acid attached to its tRNA, and the two subunits of a ribosome
are brought together.
C) An mRNA molecule transcribed from DNA is shorter than the genetic message it carries.
D) During the first step of initiation, an mRNA molecule binds to a small ribosomal subunit.
E) During the second step of initiation, a large ribosomal subunit binds to a small ribosomal subunit.

Answer 36

C) An mRNA molecule transcribed from DNA is shorter than the genetic message it carries.

Question 37

Which of the following options most accurately lists the sequence of events in translation?
A) codon recognition → translocation → peptide bond formation → termination
B) peptide bond formation → codon recognition → translocation → termination
C) codon recognition → peptide bond formation → translocation → termination
D) codon recognition → peptide bond formation → termination → translocation
E) peptide bond formation → translocation → codon recognition → termination

Answer 37

C) codon recognition → peptide bond formation → translocation → termination

Question 38

Which of the following statements regarding the flow of genetic information is false?
A) Polypeptides form proteins that determine the appearance and function of the cell and organism.
B) Eukaryotic mRNA is processed in several ways before export out of the nucleus.
C) The codons in a gene specify the amino acid sequence of a polypeptide.
D) Transcription occurs in the cytoplasm of eukaryotic cells.
E) Ribosomes function as factories that coordinate the functioning of mRNA and tRNA.

Answer 38

D) Transcription occurs in the cytoplasm of eukaryotic cells.

Question 39

Any change in the nucleotide sequence of DNA is called 
A) a mutation. 
B) an advantage. 
C) a codon. 
D) a translation. 
E) an anticodon.

Answer 39

A) a mutation.

Question 40

Consider the following sentence: "The dog did not eat." Which of the following variations of this sentence is most like a base substitution mutation? 
A) The dog did not et. 
B) The dog dog did not eat. 
C) The did dog not eat. 
D) The doe did not eat. 
E) The dog did not.

Answer 40

D) The doe did not eat.

Question 41

Consider the following sentence: "The dog did not eat." Which of the following variations of this sentence is most like a reading frame mutation? 
A) The dog dog did not eat. 
B) The did dog not eat. 
C) The dod idn ote at. 
D) The did not eat. 
E) The dog did dog did not eat.

Answer 41

C) The dod idn ote at.

Question 42

A physical or chemical agent that changes the nucleotide sequence of DNA is called a(n) 
A) reverse transcriptase. 
B) terminator. 
C) transposon. 
D) mutagen. 
E) anticodon.

Answer 42

D) mutagen.

Question 43

A protein shell enclosing a viral genome is known as a(n) 
A) capsule. 
B) envelope. 
C) phage. 
D) capsid. 
E) prophage.

Answer 43

D) capsid.

Question 44

Which of the following features characterizes the lytic cycle of a viral infection?
A) The cycle typically ends when the host bacterium divides.
B) The cycle typically leads to the lysis of the host cell.
C) The viral DNA is inserted into a bacterial chromosome.
D) The virus reproduces outside of the host cell.
E) The viral genes typically remain inactive once they are inside the host cell.

Answer 44

B) The cycle typically leads to the lysis of the host cell.

Question 45

Which of the following statements is false?
A) Some prophage genes can cause the transformation of a nonpathogenic bacterium into a form that causes human
disease.
B) Sometimes an environmental signal can trigger a switchover from the lysogenic to the lytic cycle.
C) The lysogenic cycle always occurs inside of host cells.
D) The lysogenic cycle typically results in the rapid lysis of all infected cells.
E) During a lysogenic cycle, viral DNA replication typically occurs without destroying the host cell.

Answer 45

D) The lysogenic cycle typically results in the rapid lysis of all infected cells.

Question 46

Viral DNA incorporated into host cell DNA is known as a(n) 
A) capsid. 
B) prophage. 
C) envelope. 
D) phage. 
E) genome.

Answer 46

B) prophage.

Question 47

The envelope of a flu virus
A) helps the virus enter the cell.
B) is coded by viral genes.
C) helps the virus insert its DNA into the host cell genome.
D) changes rapidly, thereby helping the virus evade an immune system response.
E) accounts for viral resistance to antibiotics.

Answer 47

A) helps the virus enter the cell.

Question 48

Which of the following statements about herpesviruses is false?
A) Herpesviruses reproduce inside the host cell’s mitochondria.
B) Herpesviruses acquire their envelopes from the host cell nuclear membrane.
C) Herpesviruses are DNA viruses.
D) Herpesviruses may remain latent for long periods of time while inside the host cell nucleus.
E) Herpesviruses may cause cold sores or genital sores to appear during times of physical or emotional stress.

Answer 48

A) Herpesviruses reproduce inside the host cell’s mitochondria.

Question 49

Which of the following statements about plant viruses is false?
A) Once in a plant, a virus can spread from cell to cell through plasmodesmata.
B) The genetic material in most plant viruses is RNA.
C) Preventing infections and breeding resistant plants can control viral infection in plants.
D) To infect a plant, a virus must first get past the plant’s epidermis.
E) There are many successful ways to rid infected plants of a virus.

Answer 49

E) There are many successful ways to rid infected plants of a virus.

Question 50

Which of the following statements regarding viral diseases is false?
A) RNA viruses tend to have an unusually high rate of mutation because their RNA genomes cannot be corrected by
proofreading.
B) New viral diseases often emerge when a virus infects a new host species.
C) Very few new human diseases have originated in other animals because the genetic differences are too great.
D) Some new viral diseases arise as a result of a mutation of existing viruses.
E) AIDS was around for decades before

Answer 50

C) Very few new human diseases have originated in other animals because the genetic differences are too great.

Question 51

What will be the most likely cause of a new avian flu pandemic like the 1918-1919 flu pandemic that killed approximately 40 million people worldwide?
A) sexual promiscuity
B) intravenous drug use and abuse
C) easy viral transmission from person to person
D) blood transfusions with tainted blood
E) increased international travel at affordable rates

Answer 51

C) easy viral transmission from person to person

Question 52

What kind of virus is HIV? 
A) a herpesvirus 
B) a paramyxovirus 
C) a retrovirus 
D) a complex virus 
E) a provirus

Answer 52

C) a retrovirus

Question 53

Which of the following enzymes does HIV use to synthesize DNA on an RNA template? 
A) ligase 
B) RNA polymerase 
C) terminator enzyme 
D) reverse transcriptase 
E) DNA convertase

Answer 53

D) reverse transcriptase

Question 54

HIV does the greatest damage to 
A) the adrenal glands. 
B) pancreatic cells. 
C) nervous tissue. 
D) gametes. 
E) white blood cells.

Answer 54

E) white blood cells.

Question 55

How do viroids harm the plants that are infected with them?
A) by increasing the plants’ metabolic rate
B) by altering the plants’ growth
C) by reducing the plants’ seed production
D) by preventing leaf production
E) by destroying the root system

Answer 55

B) by altering the plants’ growth

Question 56

Which of the following statements about the treatment or prevention for a prion infection is true?
A) Antibiotic therapies such as penicillin are very effective cures.
B) High doses of anti-inflammatory drugs such as ibuprofen reduce the symptoms of prion infections.
C) Corticosteroid therapy is the only drug therapy that can reverse the effects of a prion infection.
D) Preventative vaccines have recently been shown to be effective in preventing prion infections.
E) There is no known treatment or cure for prion infections.

Answer 56

E) There is no known treatment or cure for prion infections.

Question 57

In the 1920s, Frederick Griffith conducted an experiment in which he mixed the dead cells of a bacterial strain that can cause pneumonia with live cells of a bacterial strain that cannot. When he cultured the live cells, some of the daughter colonies proved able to cause pneumonia. Which of the following processes of bacterial DNA transfer does this experiment demonstrate? 
A) transduction 
B) conjugation 
C) transformation 
D) transposition 
E) crossing over

Answer 57

C) transformation

Question 58

Transduction
A) is the direct transfer of DNA from one bacterium to another.
B) occurs when a bacterium acquires DNA from the surrounding environment.
C) is the result of crossing over.
D) occurs when a phage transfers bacterial DNA from one bacterium to another.
E) requires DNA polymerase.

Answer 58

D) occurs when a phage transfers bacterial DNA from one bacterium to another.

Question 59

Conjugation
A) is the direct transfer of DNA from one bacterium to another.
B) occurs when a bacterium acquires DNA from the surrounding environment.
C) is the result of crossing over.
D) occurs when a phage transfers bacterial DNA from one bacterium to another.
E) requires DNA polymerase.

Answer 59

A) is the direct transfer of DNA from one bacterium to another.

Question 60

Conjugation, transformation, and transduction are all ways that bacteria
A) reduce their DNA content.
B) increase the amount of RNA in the cytoplasm.
C) change their ribosomes to eukaryotic ribosomes.
D) increase their genetic diversity.
E) alter their oxygen requirements.

Answer 60

D) increase their genetic diversity.

Question 61

A friend accidentally sends an email to you that contains a computer virus from his computer. Without knowing it, you infect your computer with the virus when you open the email. This process of spreading the computer virus using emails is most like which of the following processes? 
A) binary fission 
B) conjugation 
C) transduction 
D) transformation 
E) mitosis

Answer 61

C) transduction

Question 62

When a bacterial cell with a chromosome-borne F factor conjugates with another bacterium, how is the transmitted donor DNA incorporated into the recipient’s genome?
A) It is substituted for the equivalent portion of the recipient’s chromosome by the process of crossing over.
B) It circularizes and becomes one of the recipient cell’s plasmids.
C) The genes on the donor DNA of which the recipient does not have a copy are added to the recipient chromosome; the
remainder of the donor DNA is degraded.
D) The DNA of the recipient cell replicates, and the donor DNA is added to the end of the recipient DNA.
E) The donor and recipient DNA are both chopped into segments by restriction enzymes, and a new, composite
chromosome is assembled from the fragments.

Answer 62

A) It is substituted for the equivalent portion of the recipient’s chromosome by the process of crossing over.

Question 63

In many bacteria, genes that confer resistance to antibiotics are carried on 
A) factors. 
B) R plasmids. 
C) dissimilation plasmids. 
D) transposons. 
E) exons.

Answer 63

B) R plasmids.

Question 64

Conjugation between a bacterium that lacks an F factor (F-) and a bacterium that has an F factor on its chromosome (F+) would typically produce which of the following results?
A) The F- bacterium ends up carrying one or more plasmids from the F+ bacterium; the F+ bacterium is unchanged.
B) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F- bacterium, and the F-
bacterium ends up with an unaltered chromosome.
C) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F- bacterium, and the F-
bacterium ends up with a chromosome that lacks those genes.
D) The F- bacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+
bacterium ends up with an unaltered chromosome.
E) The F- bacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+
bacterium ends up with a chromosome that lacks those genes.

Answer 64

D) The F- bacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+
bacterium ends up with an unaltered chromosome.

Question 65

A functional F factor that is an R plasmid must contain all of the following elements except
A) genes for making sex pili.
B) genes for making the enzymes needed for conjugation.
C) a site for making the proteins needed for conjugation.
D) a site where DNA replication can begin.
E) genes for enzymes that confer resistance to antibiotics.

Answer 65

C) a site for making the proteins needed for conjugation.

Question 66

Which of the following human activities has contributed to an increase in the number of bacteria having R plasmids?
A) nitrogen fixation by genetically engineered plants
B) widespread use of childhood vaccination in developing countries
C) improper use of restriction enzymes in research and medical facilities
D) increased carcinogen exposure from excessive fossil fuel burning
E) heavy use of antibiotics in medicine and in agriculture

Answer 66

E) heavy use of antibiotics in medicine and in agriculture

Question 67

see diagram

What nucleotide sequence would be found on the partner DNA strand of the strand shown? 
A) ACTGT 
B) UGAGA 
C) TGACA 
D) TGUGU 
E) TGTCA

Answer 67

C) TGACA

Question 68

see diagram

How many origins of replication and how many replication forks are shown? 
A) 3 origins and 3 replication forks 
B) 3 origins and 6 replication forks 
C) 6 origins and 3 replication forks 
D) 6 origins and 6 replication forks 
E) 6 origins and 12 replication forks

Answer 68

B) 3 origins and 6 replication forks

Question 69

Exposure to the HIV virus doesn’t necessarily mean that a person will develop AIDS. Some people have genetic resistance to infection by HIV. Dr. Stephen O’Brien from the U.S. National Cancer Institute has recently identified a mutant form of a gene, called CCR5, that can protect against HIV infection. The mutation probably originated in Europe among survivors of the bubonic plague. The mutated gene prevents the plague bacteria from attaching to cell membranes and, therefore, from entering and infecting body cells.

Although the HIV virus is very different from the bacteria that causes the plague, both diseases affect the exact same cells and use the same method of infection. The presence of the mutated gene in descendants of plague survivors helps prevent them from contracting AIDS. Pharmaceutical companies are using this information as the basis for a new approach to AIDS prevention. This would be very important in areas of the world where the mutation is scarce or absent, such as Africa.

1) The most likely method by which the mutated CCR5 gene prevents AIDS is by
A) covering the cell membrane.
B) rupturing the nuclear membrane.
C) attacking and destroying the HIV virus particles.
D) blocking transfer RNA from reaching the viral ribosomes.
E) coding for a protective protein in the cell membrane.

Answer 69

E) coding for a protective protein in the cell membrane.

Question 70

Exposure to the HIV virus doesn’t necessarily mean that a person will develop AIDS. Some people have genetic resistance to infection by HIV. Dr. Stephen O’Brien from the U.S. National Cancer Institute has recently identified a mutant form of a gene, called CCR5, that can protect against HIV infection. The mutation probably originated in Europe among survivors of the bubonic plague. The mutated gene prevents the plague bacteria from attaching to cell membranes and, therefore, from entering and infecting body cells.

Although the HIV virus is very different from the bacteria that causes the plague, both diseases affect the exact same cells and use the same method of infection. The presence of the mutated gene in descendants of plague survivors helps prevent them from contracting AIDS. Pharmaceutical companies are using this information as the basis for a new approach to AIDS prevention. This would be very important in areas of the world where the mutation is scarce or absent, such as Africa.

2) Which of the following shows the steps of a viral infection in the proper order?
A) virus locates host cell → enters nucleus → alters host cell DNA → destroys cell membrane
B) virus locates host cell → alters host cell DNA → host cell produces copies of virus → copies enter host cell nucleus →
nucleus leaves cell
C) virus kills host cell → enters nucleus → replaces all host DNA → releases copies of virus
D) virus locates host cell → penetrates cell membrane → enters nucleus → alters host cell DNA → host cell produces
copies of virus
E) virus locates host cell → forms hydrogen bonds → changes DNA to RNA→ host cell produces copies of virus

Answer 70

D) virus locates host cell → penetrates cell membrane → enters nucleus → alters host cell DNA → host cell produces
copies of virus

Question 71

What is the difference between a gene and a allele?

Answer 71

A gene is a specific section of the chromosome where the base pairs that code for the characteristic are stored. An allele is the actual sequence of the base pairs in the section. (or slightly different version of each gene which define how characteristic shows up)
gene = eye color; allele = blue, brown (versions)

Question 72

What is the difference between the genotype and a phenotype?

Answer 72

The genotype of an organism is the genetic code in its cells. The phenotype is the visible or expressed trait, such as hair color

Question 73

3 possible genotype so?

Answer 73

Homozygous dominant, heterozygous, homozygous recessive