Exam 3 – Chpts. 9, 10

1) The best definition of a purebred plant is one that ______.
A) cannot be cross-fertilized
B) self-fertilizes to produce offspring identical to the parent
C) produces sterile offspring when cross-fertilized
D) self-fertilizes to produce hybrid offspring

B

2) A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would produce a(n) ______.
A) purebred variety
B) hybrid
C) P generation
D) F2 generation

B

3) Alleles are described as ______.
A) homologous chromosomes
B) environmental factors that affect gene expression
C) alternate versions of a gene
D) alternate phenotypes

C

4) A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The seeds of all of the offspring are yellow. Why?
A) The yellow allele is recessive to the green allele.
B) All of the offspring are homozygous yellow.
C) The yellow allele is dominant to the green allele.
D) The alleles are codominant.

C

5) A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The F1 plants have yellow seeds. What is the expected phenotypic ratio of seed color of the offspring of an F1 × F1 cross?
A) 1:2:1
B) 2:1
C) 3:1
D) 9:3:3:1

C

6) According to Mendel’s law of segregation, ______.
A) two alleles segregate into each gamete
B) more gametes carrying the dominant allele are produced than gametes carrying the recessive allele
C) gametes have one copy of each allele
D) gametes are diploid

C

7) Attached earlobes are recessive to free earlobes. What genotypic ratio is expected when an individual with attached earlobes mates with an individual heterozygous for free earlobes?
A) 2:1
B) 1:1
C) 1:2:1
D) 3:1

B

8) Mendel crossed purebred purple-flowered plants with purebred white-flowered plants, and all of the resulting offspring produced purple flowers. The offspring are all ______, and the allele for purple flowers is ______.
A) heterozygotes… recessive
B) heterozygotes… dominant
C) homozygotes… recessive
D) homozygotes… dominant

B

9) Attached earlobes are recessive to free earlobes. What is the probability of having a child with attached earlobes when an individual with attached earlobes mates with an individual heterozygous for free earlobes?
A) 0%
B) 25%
C) 50%
D) 75%

C

10) In humans, the presence or absence of dimples is a trait controlled by a single gene. What is the genotype of an individual who is heterozygous for dimples?
A) DD
B) Dd
C) dd
D) DI

B

11) An individual who is homozygous ______.
A) expresses the dominant trait
B) carries two different alleles for a gene
C) carries two copies of the same allele for a gene
D) expresses the recessive trait

C

12) Which of these crosses will only produce heterozygous offspring?
A) AA × aa
B) AA × Aa
C) Aa × Aa
D) Aa × aa

A

13) What name is given to the specific location of a gene on a chromosome?
A) locus
B) chromaddress
C) genotype
D) allele

A

14) Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). What is the expected phenotypic ratio of a cross between an RrYy and an rryy individual?
A) 1:2:1
B) 9:3:3:1
C) 3:1
D) 1:1:1:1

D

15) An individual with the genotype AaBb produces four different gametes in equal proportions. This is a demonstration of ______.
A) the chromosomal theory of inheritance
B) Mendel’s law of independent assortment
C) linkage
D) Mendel’s principle of segregation

B

16) To determine the phenotype of an individual who expresses a dominant trait, you would cross that individual with an individual who ______.
A) expresses the dominant trait
B) is homozygous recessive for that trait
C) is homozygous dominant for that trait
D) is heterozygous for that trait

B

17) A couple has two female children. What is the probability that their next child will be male?
A) 25%
B) 50%
C) 33%
D) 67%

B

18) In humans, free earlobes (E) are dominant to attached earlobes (e) and the presence of freckles (F) is dominant to the absence of freckles (f). If an individual heterozygous for both of these traits were to mate with an individual with attached earlobes and no freckles, what is the probability of having a child with attached earlobes and freckles?
A) 0%
B) 25%
C) 50%
D) 100%

B

19) The ______ is most commonly found in nature.
A) recessive trait
B) wild-type trait
C) parental
D) dominant trait

B

20) An individual heterozygous for cystic fibrosis ______.
A) cannot have children with cystic fibrosis
B) is a carrier
C) will have children who are all carriers of cystic fibrosis
D) has cystic fibrosis

B

21) Achondroplasia is a form of dwarfism caused by a dominant allele. The homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia?
A) 0%
B) 50%
C) 75%
D) 100%

B

22) Which of the following techniques is used to collect fetal cells during pregnancy for genetic testing?
A) testcross
B) dihybrid cross
C) amniocentesis
D) pedigree analysis

C

23) What is the key to the recognition of incomplete dominance?
A) The phenotype of the heterozygote falls between the phenotypes of the homozygotes.
B) The trait exhibits a continuous distribution.
C) The alleles affect more than one trait.
D) The heterozygote expresses the phenotype of both homozygotes.

A

24) An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. What is the relationship between the alleles for hair texture?
A) pleiotropy
B) incomplete dominance
C) wavy hair is dominant to both straight and curly hair
D) codominance

B

25) An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. If an individual with wavy hair mates with an individual with straight hair, what is the probability that their child will have curly hair?
A) 0%
B) 25%
C) 50%
D) 75%

A

26) What is the key to the recognition of codominance?
A) The phenotype of the heterozygote falls between the phenotypes of the homozygotes.
B) The trait exhibits a continuous distribution.
C) The alleles affect more than one trait.
D) The heterozygote expresses the phenotype of both homozygotes.

D

27) An individual with the blood group genotype LMLN has the phenotype MN. What is the relationship between the LM and LN alleles?
A) codominance
B) pleiotropy
C) LN is dominant
D) incomplete dominance

A

28) Marfan syndrome is the result of inheriting a single allele. Individuals with Marfan syndrome are tall and long-limbed, and have both cardiovascular and eye defects. The inheritance of Marfan syndrome is an example of ______.
A) codominance
B) a recessive disorder
C) pleiotropy
D) incomplete dominance

C

29) What is the key to the recognition of a trait whose expression is determined by the effects of two or more genes (polygenic inheritance)?
A) A mating between a homozygous and a heterozygous individual produces more than the expected number of offspring expressing the dominant trait.
B) All of the alleles of the gene for that trait are equally expressed.
C) Pleiotropy occurs.
D) The trait varies along a continuum in the population.

D

30) In humans, the inheritance of ______ is best explained as being polygenic.
A) cystic fibrosis
B) height
C) blood type
D) sickle-cell disease

B

31) Many human traits, such as our performance on intelligence tests or our susceptibility to heart disease, are ______.
A) determined only by our genes
B) influenced by both genes and the environment
C) determined by genes in some people and by the environment in other people
D) not affected by our genes

B

32) What is the basis of Mendel’s laws?
A) the behavior of chromosomes during prophase I of meiosis only
B) the behavior of chromosomes during mitotic anaphase
C) the behavior of chromosomes during prophase I and prophase II of meiosis
D) the behavior of chromosomes during metaphase I and anaphase I of meiosis

D

33) ______ genes violate Mendel’s principle of independent assortment.
A) Codominant
B) Linked
C) Recessive
D) Pleiotropic

B

34) What is the best explanation for a BbCc × bbcc cross producing offspring in a 5:5:1:1 phenotypic ratio?
A) linked genes
B) polygenic inheritance
C) incomplete dominance
D) codominance

A

35) A dihybrid cross produces 30 recombinant offspring out of a total of 1,000 offspring. What is the recombination frequency of the two gene pairs?
A) 6%
B) 3%
C) 30%
D) 1.5%

B

36) The recombination frequency between gene B and gene C is 11%. The recombination frequency between gene B and gene D is 5%. The recombination frequency between gene C and gene D is 15%. What would be the arrangement of these genes on a linkage map?
A) CDB
B) DBC
C) BCD
D) More information is needed.

B

37) Linked genes are usually
A) found on the X chromosome.
B) found on the Y chromosome.
C) codominant.
D) located close together on a chromosome.

D

38) Assume that having three nostrils is inherited as a sex-linked trait on the Y chromosome. A man with three nostrils has a daughter who has a son with a man who has only two nostrils. What is the probability that the three-nostriled man’s grandson has three nostrils?
A) 0%
B) 25%
C) 50%
D) 100%

A

39) Red-green color blindness is inherited as a sex-linked recessive trait. The gene is found on the X chromosome. How can a man with normal color vision father a daughter who is red-green color-blind?
A) The woman with whom he mates is red-green color-blind.
B) The man is heterozygous for red-green color blindness.
C) He can’t (unless there is a mutation).
D) The man’s mother carries an allele for red-green color blindness, and the expression of the trait skipped a generation.

C

40) Hypophosphatemia (vitamin D-resistant rickets) is inherited as an sex-linked dominant trait. The relevant gene is found on the X chromosome. What is the expected outcome of a cross between a homozygous recessive woman and a man with hypophosphatemia?
A) All of their daughters and none of their sons exhibit hypophosphatemia.
B) Fifty percent of their daughters and fifty percent of their sons exhibit hypophosphatemia.
C) All of their sons and none of their daughters exhibit hypophosphatemia.
D) Twenty-five percent of their offspring exhibit hypophosphatemia.

A

41) In the accompanying art you see a table with the actual number of offspring that resulted from a dihybrid cross. The numbers do not show the 9:3:3:1 ratio predicted. One phenotype occurred more than predicted; another occurred less. The reason could be because ______.
A) of errors in mitosis
B) some of the alleles were linked
C) some of the alleles were sex-linked
D) of polygenic inheritance

B

42) Recombinant offspring were produced by the mating shown in the accompanying art. What is the recombination frequency of purple round and red long offspring?
A) 21%
B) 381
C) 21 + 21
D) 11%

D

43) Mary has the genotype ______.
A) WW
B) ww
C) Ww
D) more information is needed.

C

44) Janice’s genotype is _______.
A) Ww
B) WW
C) ww
D) WW or Ww

D

45) This pedigree supports the fact that widow’s peak is due to a dominant allele, because if it were due to a recessive allele and both parents show the recessive phenotype, then ______.
A) none of the sons would have a widow’s peak
B) all of the offspring would have a widow’s peak
C) none of the daughters would have a widow’s peak
D) all of the daughters and none of the sons would have a widow’s peak

B

46) What would genetic counselors say is the probability that the second child will have the disease?
A) 1/2
B) 1/4
C) 1/8
D) 1/16

B

1) DNA and RNA are polymers composed of ______ monomers.
A) nucleotide
B) carbohydrate
C) fatty acid
D) amino acid

A

2) The backbone of DNA consists of ______.
A) nitrogenous bases
B) a repeating sugar-nucleotide-sugar-nucleotide pattern
C) a repeating sugar-phosphate-sugar-phosphate pattern
D) paired nucleotides

C

3) Thymine and cytosine differ from adenine and guanine in that
A) thymine and cytosine are single-ring structures, whereas adenine and guanine are double-ring structures.
B) thymine and cytosine are only found in DNA, whereas adenine and guanine are found in both DNA and RNA.
C) thymine and cytosine are only found in DNA, whereas adenine and guanine are only found in RNA.
D) thymine and cytosine are larger nitrogenous bases.

A

4) RNA contains the nitrogenous base ______ instead of ______, which is only found in DNA.
A) a deoxyribose sugar… a ribose sugar
B) uracil… thymine
C) uracil… guanine
D) thymine… uracil

B

5) If adenine makes up 20% of the bases in a DNA double helix, what percent of the bases are guanine?
A) 60%
B) 40%
C) 20%
D) 30%

D

6) In a DNA double helix, adenine pairs with ______ and guanine pairs with ______.
A) cytosine… thymine
B) guanine… adenine
C) thymine… cytosine
D) uracil… cytosine

C

7) If one strand of a DNA double helix has the sequence GTCCAT, what is the sequence of the other strand?
A) ACTTGC
B) TGAACG
C) CAGGTA
D) CAGGUA

C

8) Who discovered the structure of DNA?
A) Pauling
B) Watson and Crick
C) Franklin
D) Hershey and Chase

B

9) Evidence for the spiral nature of DNA came from ______.
A) X-ray crystallography studies
B) studies of disease-causing bacteria
C) base rule studies
D) bacteriophage studies

A

10) What type of chemical bond joins the bases of complementary DNA strands?
A) ionic
B) covalent
C) hydrophilic
D) hydrogen

D

11) After replication, ______.
A) each new DNA double helix consists of two old strands
B) each new DNA double helix consists of one old strand and one new strand
C) each new DNA double helix consists of two new strands
D) one new DNA double helix consists of two old strands and the other new DNA double helix consists of two new strands

B

12) DNA replication
A) is a slow process that results in virtually no errors.
B) requires DNA polymerase and RNA polymerase.
C) is a very fast process that results in numerous errors.
D) requires the cooperation of over a dozen enzymes and other proteins.

D

13) The modern phrasing of Beadle and Tatum’s hypothesis about relationships between genes and their products is "one gene-one ______."
A) enzyme
B) RNA
C) protein
D) polypeptide

D

14) What name is given to the collection of traits exhibited by an organism?
A) holotype
B) genotype
C) phenotype
D) morphology

C

15) How many amino acids are common to all living systems?
A) 10
B) 20
C) 30
D) 100

B

16) How many nucleotides make up a codon?
A) two
B) three
C) four
D) five

B

17) The shared genetic code of all life on Earth is evidence that ______.
A) the genetic code arose relatively late in the history of life on Earth
B) DNA replication is error-free
C) all life shares a common ancestry
D) bacterial cells arose earlier than eukaryotic cells

C

18) Transcription is the ______.
A) manufacture of a strand of RNA complementary to a strand of DNA
B) manufacture of two new DNA double helices that are identical to an old DNA double helix
C) modification of a strand of RNA prior to the manufacture of a protein
D) manufacture of a protein based on information carried by RNA

A

19) If a strand of DNA has the sequence AAGCTC, transcription will result in a(n) ______.
A) single RNA strand with the sequence TTCGAG
B) DNA double helix with the sequence AAGCTC for one strand and TTCGAG for the complementary strand
C) single RNA strand with the sequence UUCGAG
D) RNA double helix with the sequence UUCGAG for one strand and AAGCUC for the complimentary strand

C

20) Which of the following enzymes is responsible for RNA synthesis?
A) RNase
B) RNA helicase
C) RNA ligase
D) RNA polymerase

D

21) The region of DNA where RNA synthesis begins is the ______.
A) start codon
B) promoter
C) initiator
D) processor

B

22) The correct sequence of events occurring during transcription is ______.
A) splicing, capping, tailing
B) initiation, elongation, termination
C) tailing, capping, splicing
D) elongation, initiation, termination

B

23) The absence of a terminator in transcription will result in ______.
A) the creation of a virus
B) a strand of mRNA that lacks its cap and tail
C) the production of a longer RNA molecule
D) the production of a shorter RNA molecule

C

24) What protects mRNA from attack by cellular enzymes?
A) RNA splicing
B) the removal of exons
C) the lack of RNA-digesting enzymes in the cytoplasm
D) a cap and tail

D

25) The expressed (coding) regions of eukaryotic genes are called ______.
A) caps
B) promoters
C) exons
D) introns

C

26) Translation converts the information stored in ______ to ______.
A) DNA… RNA
B) RNA… a polypeptide
C) DNA… a polypeptide
D) RNA… DNA

B

27) The RNA that is translated into a polypeptide is ______ RNA.
A) nuclear
B) ribosomal
C) transfer
D) messenger

D

28) The DNA codon AGT codes for an amino acid carried by a tRNA with the anticodon ______.
A) TCU
B) AGU
C) TCA
D) AGT

B

29) Where is translation accomplished?
A) lysosomes
B) smooth endoplasmic reticulum
C) ribosomes
D) nucleoli

C

30) During translation, what is the correct order of events that occur as an amino acid is added?
A) codon recognition, peptide bond formation, translocation
B) translocation, codon recognition, termination
C) initiation, codon recognition, termination
D) peptide bond formation, translocation, codon recognition

A

31) Peptide bonds form between ______.
A) amino acids
B) an mRNA codon and a tRNA anticodon
C) a tRNA and the amino acid it is carrying
D) an mRNA transcript and the small ribosomal subunit

A

32) A mutation within a gene that will insert a premature stop codon in mRNA would ______.
A) result in a polypeptide that is one amino acid shorter than the one produced prior to the mutation
B) result in a shortened polypeptide chain
C) change the location at which transcription of the next gene begins
D) have the same effect as deleting a single nucleotide in the gene

B

33) What is the smallest number of nucleotides that must be added or subtracted to change the triplet grouping of the genetic message?
A) one
B) two
C) three
D) four

A

34) What is the ultimate source of all diversity?
A) natural selection
B) sexual recombination
C) meiosis
D) mutation

D

35) Mad cow disease is caused by
A) a retrovirus similar to HIV.
B) an enveloped virus.
C) small circular RNA molecules called viroids.
D) infectious proteins called prions.

D

36) How can bacteriophage DNA be spread from cell to cell without causing cell death?
A) by altering the way a cell splices its RNA
B) via a lytic cycle
C) via a lysogenic cycle
D) by altering its DNA

C

37) Plant viruses ______.
A) often use RNA, rather than DNA, as their genetic material
B) benefit plants, rather than causing disease
C) cause diseases that can be easily cured
D) do not exist-viruses only attack animals

A

38) A(n) ______ is to bacteria as a ______ is to animal cells.
A) retrovirus… virus
B) phage… prophage
C) prophage… provirus
D) RNA virus… DNA virus

C

39) HIV (human immunodeficiency virus) must use its own ______ to reproduce.
A) DNA polymerase
B) reverse transcriptase
C) RNA polymerase
D) tRNA

B

40) The figure below shows the flow of genetic information in a eukaryotic cell. The transfer of information from DNA into an RNA molecule is known as ______.
A) DNA replication
B) transcription
C) polypeptide
D) translation

B

41) Examine the genetic code table, shown below. The codon AGC codes for the amino acid ______.
A) serine
B) arginine
C) threonine
D) alanine

A

42) Consider the following figure. It indicates that a single amino acid substitution ______.
A) always involves adenine and uracil
B) may alter a protein so that it no longer functions properly
C) is a silent mutation
D) causes a nonsense mutation

B

43) The first thing you notice is that there is no immediate increase in viruses following infection. This is because ______.
A) it takes the virus time to adapt to the host
B) although the virus has infected the host, it takes time to complete the lytic cycle
C) the host is immune to the virus
D) the virus is in a lysogenic cycle throughout the experiment

B

44) Once viruses are detected, the number of viruses increases rapidly. This is because ______.
A) lysogeny produces large numbers of bacteriophages
B) DNA viruses reproduce more rapidly than RNA viruses
C) the host cell speeds the release process
D) the viruses lyse the hosts to release mature viruses all at once

D

45) The mutation that resulted from her accident was probably ______.
A) an amino acid substitution
B) one that changed the triplet grouping of the genetic message
C) an error in translation
D) a loss in regulation of gene expression

B

46) The mutation would be most harmful to the cells if it resulted in ______.
A) a single nucleotide insertion near the start of the coding sequence
B) a single nucleotide deletion near the end of the coding sequence
C) a single nucleotide in the middle of an intron
D) deletion of a triplet near the middle of the gene

A