Genetics Exam II

1. In forming a nucleotide, phosphorus is most often attached to the nucleoside at the C-5' position of the sugar.

True

False

2. The fertility factor is a mobile genetic element called a plasmid that contains genes for directing gene transfer between bacterial cells.

True

False

3. A human with XXY sex chromosomes is female because she has two X chromosomes.

True

False

4. Fragile X syndrome is thought to be caused by the inactivation of a gene spanning the fragile region on the X chromosome due to a large number of trinucleotide repeats just upstream from the coding sequence of the gene.

True

False

5. Organelle heredity, maternal effect, and infectious heredity are all examples of extranuclear inheritance, which is the transmission of genetic information to offspring through the cytoplasm rather than through the nucleus.

True

False

6. An E. coli nutritional mutant is described as an auxotroph, which requires minimal medium with supplementation of an organic carbon source or inorganic ion for growth.

True

False

7. Guanine and adenine are purines found in DNA.

True

False

8. A human with the karyotype 49,XXXYY forms two Barr bodies.

True

False

9. The paternal X is always inactivated for dosage compensation in placental mammals.

True

False

10. A cross between a tetraploid and a diploid member of the same species will produce offspring that can undergo sexual reproduction.

True

False

11. Females with only one X chromosome do not develop; this condition is lethal.

True

False

12. In the yeast Saccharomyces cerevisiae, suppressive petite mutants exhibit Mendelian inheritance because they result from nuclear mutations.

True

False

13. A plaque assay detects the number of bacterial auxotrophs on a plate.

True

False

14. Which of the following statements about Barr bodies is true?

They contain no DNA.

They are inactivated Y chromosomes.

They ensure that males and females have equal "doses" of the genes on the X chromosome.

They are visible only in males.

15. Hfr bacterial cells exhibit high levels of gene transfer because

They do not require conjugation for gene transfer.

Rather than existing as an isolated plasmid, the F factor is incorporated into the bacterial chromosome.

They contain two distinct F factors.

They induce the production of significantly more sex pili than normal F+ cells.

16. Watson and Crick used information from several individuals to construct their model of DNA. Whose X-ray diffraction studies were critical to their work?

Linus Pauling

Phoebus Levene

Maurice Wilkins

Rosalind Franklin

17. In a sexually reproducing diploid species, gametes must be

Diploid.

Male or female.

Produced via mitosis.

Haploid.

18. Chrysanthemums have a haploid chromosome number of 9. How many chromosomes are found in tetraploid chrysanthemum species?

72

36

9

18

19. Which condition produced from an autosomal trisomy results in survival to adulthood?

Patau syndrome

Edwards syndrome

Cri-du-chat syndrome

Down syndrome

20. What is the specific term that describes the loss of a single chromosome (2n - 1)?

Monosomy

Trisomy

Aneuploidy

Monoploidy

21. Why would the transmission of Down syndrome resulting from a Robertsonian translocation be unaffected by the age of the mother?

Down syndrome resulting from a Robertsonian translocation does not result from nondisjunction, which is affected by age.

This statement is incorrect; the age of the mother does affect the transmission of Down syndrome resulting from Robertsonian translocations.

Mothers with a Robertsonian translocation never have children.

Robertsonian translocations occur only in young mothers.

22. Which of the following terms can be used to describe Down syndrome?

Triploid and aneuploid

Trisomy and polyploid

Trisomy and aneuploid

Triploid and polyploid

23. Why is it important for a retrovirus to carry its own reverse transcriptase protein instead of making it from its reverse transcriptase gene after it infects a cell?

It is not important; the virus can make its own reverse transcriptase from its viral RNA after infection.

The viral reverse transcriptase is different from the host cell's reverse transcriptase.

24. Which of the following statements about DNA structure is true?

The pentose sugar in DNA is ribose.

Nucleic acids are formed through phosphodiester bonds that link nucleosides together.

Hydrogen bonds formed between the sugar-phosphate backbone of the two DNA chains help to stabilize DNA structure.

The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.

25. What is the complementary DNA sequence to a 5' ATGCTTGACTG 3'?

5' TACGAACTGAC 3'

5' CAGTCAAGCAT 3'

5' ATGCTTGACTG 3'

5' ACTCTACGTAG 3'

26. The hypothesis that gene duplication is essential to evolution is supported by the existence of

Fragile sites.

Gene families.

Intercalary deletions.

Inversions.

27. A child is born with Down syndrome. Analysis of his karyotype shows two number 21 chromosomes, a single number 18 chromosome, and an additional large chromosome about the size of chromosome 3. Which of the following conclusions can be drawn from the karyotype?

The large chromosome represents a deleted chromosome number 1.

The large chromosome represents a Robertsonian fusion between chromosomes 21 and 18.

There is too little information about chromosome 21 to draw a conclusion.

The large chromosome represents an extra chromosome 3.

28. When a bacterial cell is transformed, after one round of cell division, only one of the two resulting cells contains new genetic material because

The original gene, still floating in the cytoplasm, may be used when replicating the chromosome.

At transformation, a heteroduplex is formed that alters only one strand of the DNA, leaving the other unchanged.

Many cells reject newly integrated genes.

Transformed cells are initially heterozygous.

29. Leaf coloration in the four‑o'clock plant, Mirabilis jalapa, was one of the first examples of cytoplasmic inheritance. If ovules from a variegated‑leafed branch are pollinated with pollen from a variegated‑leafed branch, what phenotypes will be observed in the progeny?

All white‑leafed progeny

White‑ and green‑leafed progeny

All variegated‑leafed progeny

All green‑leafed progeny

30. Which human genetic disease does not exhibit cytoplasmic maternal inheritance?

Kearns-Sayre syndrome

Leber's hereditary optic neuropathy

Hemophilia

Myoclonic epilepsy

31. Which human aneuploid condition does not involve a sex chromosome?

Turner syndrome

Familial Down syndrome

Fragile X syndrome

Trisomy 21

32. Which of the following statements about dosage compensation is true?

It is a problem in species that have more autosomes than sex chromosomes.

It cannot be directed by a master switch that enhances X-chromosome activity.

Its mechanism is the same in all animals.

It must occur when one sex has more copies of a gene or genes than the other sex.

33. Which of the following crosses could produce a right‑hand coiled shell heterozygote in the snail Limnaea peregra, if the gene D, which codes for right‑hand coiled shells, is dominant to the gene d, which codes for left‑hand coiled shells?

Left‑hand coiled DD female × right‑hand coiled DD male

Right‑hand coiled dd female × right‑hand coiled dd male

Left‑hand coiled dd female × right‑hand coiled DD male

Right‑hand coiled Dd female × right‑hand coiled Dd male

34. Which gametes will be produced if nondisjunction occurs during the second meiotic division?

All haploid gametes

Two haploid gametes, one diploid gamete, and one gamete missing a copy of one of the chromosomes

Two diploid gametes and two haploid gametes

All trisomic gametes

35. Which of the following statements about double fertilization is true?

It results in individuals with an extra copy of one of the sex chromosomes.

It is the mechanism by which monozygotic, but not dizygotic, twins are produced.

It is the mechanism by which two sperm nuclei fertilize an oocyte and two endosperm nuclei, respectively.

It is the mechanism by which dizygotic, but not monozygotic, twins are produced.

36. What is a merozygote?

A haploid bacterial cell

The result of sexual reproduction between two bacteria cells

A partially diploid bacterial cell

A zygote formed from a bacteriophage and a bacterial cell

37. All of the following statements about bacteriophages are true except that

They are viruses.

They can pick up bacterial genes during the process of infecting a bacterial cell.

Within their heads, they can pack the main chromosome from one cell and transfer it to another.

They use the metabolic machinery of a bacterial cell to produce more copies of themselves.

38. What observation did Griffith make in his experiment with Streptococcus pneumoniae?

The mouse survived injection of live virulent (smooth) Streptococcus pneumoniae.

That DNA is the genetic material.

The heat-killed, virulent Streptococcus pneumoniae was lethal to the mouse.

39. What results did Avery, McLeod and McCarty obtain in their experiments with virulent bacteria?

Protease destroyed the transforming activity.

DNase destroyed the transforming activity.

RNase destroyed the transforming activity.

The transforming principle was too complex and difficult to be purified.

40. What proportions of progeny would be expected from a cross between streptomycin‑sensitive mt⁺ and streptomycin‑resistant mt^– strains of the algaChlamydomonas reinhardi?

All streptomycin‑sensitive mt+

All streptomycin‑resistant mt–

One‑half streptomycin‑resistant mt+ and one‑half streptomycin‑resistant mt–

One‑half streptomycin‑sensitive mt+and one‑half streptomycin‑sensitive mt–

41. How can duplications arise?

A chromosome break and exchange

Uneven crossing over during meiotic prophase

Spindle failure during chromosome separation

Loss of a telomere

42. The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age. Which of the following errors most likely produces this condition?

Nondisjunction during either meiosis I or II in the male gamete

Nondisjunction during meiosis I in either the male and female gamete

Nondisjunction during meiosis II in either the male and female gamete

Nondisjunction during either meiosis I or II in the female gamete

43. What is transduction?

Viral‑mediated viral recombination

Bacterial‑mediated bacterial recombination

Viral‑mediated bacterial recombination

Bacterial‑mediated viral recombination

44. Which of the following statements about the difference between DNA and RNA is false?

RNA is usually much longer than DNA.

DNA is usually double-stranded.

RNA has a free 2' hydroxyl group.

The DNA base composition must have the amount of purines equal to the amount of pyrimidines.

45. Which of the following statements about maternal inheritance is true?

In maternal inheritance, reciprocal crosses give identical results but with different ratios among male and female progeny.

In maternal inheritance, the genes are linked to the X chromosome.

46. Which of the following statements about individuals with Klinefelter syndrome or Turner syndrome is false?

Individuals with either syndrome have 44 autosomes.

Both syndromes can be identified by a karyotype.

Individuals with either syndrome are both identified as females.

Both syndromes result from nondisjunction.

47. Which of the following elements is not involved in conjugation?

Transformation

Sex pilus

Bacterial contact

Plasmids

48. If a double-stranded sample of DNA has a base composition of 20% guanine, which of the following statements is true?

The amount of the other purine adenine must also equal 20%.

The amount of cytosine must be equal to 30% so that the total amount of G + C equals 50%.

The amount of thymine must equal 30%.

The ratio of purines to pyrimiidines must be greater than 1.

49. What is the diploid chromosome number of an individual with both Klinefelter syndrome and Down syndrome (three copies of chromosome 21)?

45

46

47

48

50. Which of the following phenotypic descriptions does not describe a mitochondrial trait?

Petite in Saccharomyces cerevisiae

Kearns–Sayre syndrome in humans

Poky in Neurospora crassa

Streptomycin resistance in Chlamydomonas reinhardi

51. What is the general term for a condition in which the chromosome number is not a multiple of a complete set?

Triploidy

Aneuploidy

Polyploidy

Trisomy

52. Chromosomal aberrations may be characterized by all of the following except

Chromosome loss

Translocations

Frameshift mutations

Inversions

53. Which term best describes an individual with Klinefelter syndrome?

Triploid

Aneuploid

Polyploid

Euploid

54. The normally cultivated cotton plant is a tetraploid (52 chromosomes). How many chromosomes did the probable ancestral haploid have?

52

26

13

104

55. Why do some organisms use both sexual and asexual reproduction?

The two modes of reproduction maximize the genetic variation within a species.

The organisms are hermaphroditic.

The two modes of reproduction are favored under different conditions.

The organisms are monoecious.

56. All of the following are mechanisms by which sex can be determined except

The presence of two X chromosomes or an X and a Y chromosome.

The ratio of X chromosomes to the number of sets of autosomes.

The temperature at which the eggs are incubated.

The number of Barr bodies present.

57. Which of the following statements best describes lysogeny?

An infected bacterial cell is immediately ruptured following rapid replication of the phage DNA.

A phage infects a bacterium, and the phage DNA lives symbiotically within the F‑factor plasmid in the cell.

Viral DNA is integrated into the bacterial DNA and passed on harmlessly with each round of replication and cell division.

Chemical or UV light treatment renders the viral DNA harmless to the bacterial cell.

58. How is genetic information transferred during conjugation?

Bidirectionally between two cells

From one bacterium to another

With the help of a viral go‑between

From one cell into the culture medium, where it is taken up by another cell

59. Which of the following syndromes is not paired with its causative chromosomal aberration?

Fragile X syndrome-deletion

Cri-du-chat syndrome-deletion

Down syndrome-Robertsonian translocation

Huntington's disease-duplication

60. The effect of Barr body formation in mammals is that

Females are mosaics for homozygous X-linked genes.

Females are mosaics for heterozygous X-linked genes.

Males are mosaics for hemizygous X-linked genes.

Females are mosaics for heterozygous autosomal genes.

61. Which of the following statements about the Cot1/2 or half-association value of DNA fragments is true?

A longer DNA molecule would associate more quickly (smaller Cot1/2 value).

Molecules with the highest GC content would associate more slowly.

DNA with more repeated sequences requires more time to reassociate (smaller Cot value).

Shorter DNA molecules would associate more quickly (smaller Cot1/2 values).

62. Which of the following statements about the endosymbiotic theory is false?

Mitochondria and chloroplasts arose independently from free‑living bacteria.

The ancestral bacteria from which mitochondria and chloroplasts are derived were capable of photosynthesis and aerobic respiration.

The entire genome of the ancestral bacteria has been preserved in present‑day mitochondria and chloroplasts.

63. Which genetic disease is caused by a trisomy for chromosome 13?

Cri-du-chat syndrome

Edwards syndrome

Down syndrome

Patau syndrome

64. What distinguishes paracentric inversions from pericentric inversions?

Inclusion of the centromere in the inversion.

One suppresses crossovers; the other encourages crossovers.

The placement of the centromere in the inversion.

The formation of dicentric bridges.

65. Which of the following statements about nondisjunction is false?

It separates maternal from paternal chromatids.

It occurs more frequently in human females over age 35.

It may fail to separate maternal chromatids from one another or paternal chromatids from one another.

It may fail to separate maternal from paternal chromatids.

66. The sporophyte stage in plants

Occurs only within the megaspore mother cell.

Is diploid and produces haploid spores.

Is linked to the haploid phase via mitosis.

Is diploid and produces diploid spores.

67. Bacterial cells are always haploid unless

They are simultaneously infected by two Hfr strains.

None of these choices. They are always haploid.

They are infected with a transforming phage that has been incubated with bacteria from the same strain.

68. Which enzyme makes DNA from an RNA template?

RNA polymerase

DNA polymerase

Reverse Transcriptase

Replicase

69. To which positions in the sugar of a deoxyribonucleotide can a phosphate be esterified?

C-3' and C-5'

C-5'

C-1', C-2', and C-3'

C-1' and C-5'

70. Leber's hereditary optic neuropathy is caused by a mutation in the mitochondrial gene encoding NADH dehydrogenase. The trait exhibits cytoplasmic inheritance and is passed along maternal lines. Often, however, both parents of an affected individual are phenotypically normal, and there is no family history of the disease. What is the most likely explanation for this observation?

The mother was heterozygous, and the gamete that formed the zygote did not carry the mutant allele.

The mother exhibited incomplete penetrance for the trait.

The disease does not affect females, only males.

A new mutation arose in the mitochondrial genome.

71. How does the Y chromosome determine maleness in humans?

By containing the autosomal genes responsible for the SRY effects

By containing the genes for steroid metabolism

By containing a gene coding for the TDF, which directs the development of fetal gonads

By containing the structural genes for testes production

72. What is one explanation for the difference between the primary sex ratio and the secondary sex ratio in humans?

Women live significantly longer than men.

Y-bearing sperm are better swimmers than X-bearing sperm.

More boys die during infancy than girls.

There is disproportionate death of female fetuses prior to birth.

73. What results would be expected from a plaque assay if the dilution factor of the phage‑infected culture were too low?

The plate would have a few plaques.

The entire lawn of bacteria would be lysed.

None of these choices

The plate would have no plaques.

74. Which of the following statements does not describe Z-DNA?

The sugar phosphate backbone of Z-DNA assumes a zigzag course through space.

Z-DNA is a typical of GC-rich sequences.

It forms a left-handed helix.

The strands are not antiparallel.

75. What conclusion could be drawn if Hershey and Chase had found only 35S in their bacterial cells?

No conclusion is possible.

DNA and protein together serve as the genetic material.

DNA is the genetic material.

Protein is the genetic material.

76. Leaf coloration in the four‑o'clock plant, Mirabilis jalapa, was one of the first examples of cytoplasmic inheritance. If ovules from a white‑leafed branch are pollinated with pollen from a green‑leafed branch, what phenotypes will be observed in the progeny?

All white‑leafed progeny

White‑ and green‑leafed progeny

All variegated‑leafed progeny

All green‑leafed progeny

77. Which of the following statements about the roundworm C. elegans is false?

No individuals are exclusively female.

The lineage of every adult cell can be traced back to its embryonic origins.

Adults are very simple, consisting of approximately 1000 cells.

Males have a Y chromosome, and hermaphrodites have an X chromosome.

78. Which of the following statements about XYY males is true?

They are generally taller than average.

They are sterile.

They are likely to end up in prison.

They have underdeveloped secondary sex characteristics.

79. In maize, there are mutant genes that confer male sterility to all of the offspring of the female parent carrying this genotype. This genetic information is not found on any of the chromosomes that make up the maize genome. What is the most likely mode of inheritance for these genes?

Transgenic inheritance

Extrachromosomal inheritance

Pseudoinheritance

Biparental inheritance

80. Of the following DNA strands in combination with their complementary strands (forming double helices), three undergo a hyperchromic shift with a Tm of about 42C. Which one has a Tm of 52C?

ATTGAGTGTA

CTTAAATTTG

AAATTTGGGA

TCATGCGATC

81. Which technique can be used to identify the location of genes on a chromosome?

FISH

X-ray diffraction analysis

Reassociation kinetics

Electrophoresis

82. If two DNA strands of identical length were analyzed, which of the following statements would be true of their Tm or melting temperature?

DNA with a low AT content would melt more slowly.

All DNA strands of equal length have equal melting temperatures.

The DNA with the greater number of repetitive sequences will melt more slowly (lower Tm).

DNA with a high GC content must have a lower Tm.

83. Which of the following human genetic diseases is caused by a segmental deletion (partial monosomy)?

Fragile X syndrome

Turner syndrome

Cri-du-chat syndrome

Edwards syndrome

84. What phenotype would be expected in balanced translocation heterozygotes in the absence of position effects?

Normal, even though they have too much genetic material

Abnormal, because they have too much genetic material

Normal, because they have a normal amount of genetic material

Abnormal, because they lack some genetic material

85. How is sex determined in Drosophila?

By the ratio of the number of X chromosomes to the number of sets of autosomes

By the ratio of the number of Y chromosomes to the number of sets of autosomes

By the ratio of the number of X chromosomes to the number of autosomes

By the ratio of the number of Y chromosomes to the number of autosomes

86. Which of the following statements is not true of Hfr bacteria?

They function as the donor in crosses with F− bacteria.

They are derived from F+ bacteria.

They frequently convert recipient bacteria to F+ cells.

87. How is a merozygote formed?

The F factor is inserted into the chromosome of an F− cell, causing it to become an Hfr strain.

The F factor is excised from the chromosome of an Hfr strain, causing it to revert to F−.

The F factor is inserted into the chromosome of an F+ cell, causing it to revert to F−.

88. Which of the following statements best describes the structure of a DNA molecule?

DNA is composed of a sugar-phosphate backbone with bases projecting toward the inside of the backbone.

DNA is composed of a sugar-phosphate backbone with bases projecting toward the outside of the backbone.

DNA is composed of a sugar-phosphate backbone made up of bases hydrogen-bonded to each other.

DNA is composed of a deoxynucleoside triphosphate with a base attached to it.

89. The direction of coiling in the snail Limnaea peregra is determined by the genotype of the maternal parent producing the egg, regardless of the progeny's genotype. Which of the following statements correctly describes this trait?

It is a sex-influenced trait.

The trait is an example of maternal inheritance.

It is an X-linked trait.

The trait is an example of maternal influence.

90. Which of the following crosses could produce a left‑hand coiled shell heterozygote in the snail Limnaea peregra, if the gene D, which codes for right‑hand coiled shells, is dominant to the gene d, which codes for left‑hand coiled shells?

Left‑hand coiled Dd female × left‑hand coiled dd male

Left‑hand coiled DD female × left‑hand coiled dd male

Right‑hand coiled dd female × left‑hand coiled DD male

Left‑hand coiled DD female × right‑hand coiled dd male

91. Which term specifically refers to the gain of extra chromosome sets from individuals of the same species?

Allopolyploidy

Autopolyploidy

Euploidy

Triploidy

92. Which of the following statements about the T4 lytic life cycle is false?

The phage produces lysozyme, which ruptures the host cell wall and releases newly formed viral particles.

The bacterial DNA is degraded.

The phage takes over the protein synthesis machinery of the bacteria.

The phage DNA is injected into the host and integrates into the bacterial chromosome.

93. Which of the following is true of thymine?

Thymine can never be attached to ribose.

Thymine is the same as 5-methyl uracil.

Thymine has an amino group at the C-4 position.

Thymine has a methyl group attached to the N-1 position.

94. RNA differs from DNA in all of the following ways except by

The sugar molecule.

The 5'-3' orientation of the polynucleotide strand.

The presence of uracil.

The number of different functions performed.

95. Which term describes the condition in which cells have a variable mixture of organelles with different genetic origins?

Heteroduplex

Heteroplasmy

Heterokaryon

Heterozygous

96. Which of the following is an example of infectious heredity?

Petite mutations in Saccharomyces cerevisiae

Shell coiling in Limnaea peregra

Variegation in Mirabilis jalapa

High female sex ratio in Drosophila bifasciata and Drosophila willistoni

97. Which human chromosomes have been observed in an aneuploid condition in fetuses?

Chromosomes 21, 18, and 13

Only the sex chromosomes X and Y

X, Y, and chromosome 21

All chromosomes

98. What are pseudoautosomal regions on the sex chromosomes?

Regions of the X and Y chromosomes that don't recombine during meiosis

Homologous regions of the X and Y chromosomes

Homozygous regions of autosomal chromosomes

Hemizygous regions of the X and Y chromosomes

99. Why is it easier to identify spontaneous mutations in bacteria than in most eukaryotes?

They can be induced via exposure to the bacteriophage T1.

They are expressed directly in descendant cells because bacteria are haploid.

They occur at a much higher frequency.

They are visible as color changes within a bacterial plaque.

100. What limits E. coli growth within a medium culture?

All of these choices

Physical space

Carbon dioxide

Nutrients and oxygen

101. Which of the following statements about cotransformation is true?

Unlinked genes are passed simultaneously from one cell to another.

Two bacterial cells within a culture are transformed by the same genetic material.

A bacterial cell receives two adjacent genes on a single piece of DNA from the medium.

It is not uncommon for the entire bacterial chromosome and F factor to be passed from one cell to another.

102. What does intergenic mapping involve?

Mapping genes by observing recombination between a virus and a bacterial genome

Gene mapping within a species

Mapping between genes

Mapping genes by observing recombination between two different virus genomes

103. How does recombination in bacteria differ from recombination in eukaryotes?

Sister chromatids, not homologous chromosomes, exchange information during recombination.

A portion of DNA from one genome is replaced with homologous DNA from another strain of bacteria.

Only the plasmid DNA goes through recombination in prokaryotes.

Recombination does not occur in prokaryotes.

104. Forty-eight plaques were counted on a plate when 0.1 ml of bacteriophage-infected bacteria from a 10⁻⁶ dilution of a 10‑ml culture was plated. The original bacteriophage density was

48 × 10^7

4.8 × 10^−7

48 × 10^−6

4.8 × 10^6

105. Which of the following statements about conjugation is true?

DNA is transferred from an F+ cell to an F− cell.

Only competent cells can undergo conjugation.

The F factor is an element that is found in the chromosome of an F+ cell.

106. How many chromosomes would be found in an allopolyploid plant if its parents had diploid numbers of 4 and 6 respectively?

Diploid number of 5

Diploid number of 12

Haploid number of 5

Haploid number of 10

107. In an Hfr mating with an F⁻cell, why doesn't the recipient cell always become an Hfr or F⁺ cell?

F−cells become F+ or Hfr cells only if the mating is interrupted before a complete chromosome is transferred.

Some Hfr cells do not carry the F factor.

Hfr cells often carry the F factor in a free‑floating plasmid that is not transferred.

The F factor is the last part of the chromosome to be transferred.

108. If Avery, MacLeod, and McCarty had determined that the transforming molecule was a protein, what experimental results would not have been observed?

Heat-killed cultures treated with DNase would transform the R cells.

Heat-killed cultures treated with protease would not transform the R cells.

Heat-killed cultures treated with RNase would transform the R cells.

Heat-killed cultures treated with protease would transform the R cells.

Genetics Exam II

1. In forming a nucleotide, phosphorus is most often attached to the nucleoside at the C-5' position of the sugar.

2.

What first name or nickname would you like us to use?

2. The fertility factor is a mobile genetic element called a plasmid that contains genes for directing gene transfer between bacterial cells.

3. A human with XXY sex chromosomes is female because she has two X chromosomes.

4. Fragile X syndrome is thought to be caused by the inactivation of a gene spanning the fragile region on the X chromosome due to a large number of trinucleotide repeats just upstream from the coding sequence of the gene.

5. Organelle heredity, maternal effect, and infectious heredity are all examples of extranuclear inheritance, which is the transmission of genetic information to offspring through the cytoplasm rather than through the nucleus.

6. An E. coli nutritional mutant is described as an auxotroph, which requires minimal medium with supplementation of an organic carbon source or inorganic ion for growth.

7. Guanine and adenine are purines found in DNA.

8. A human with the karyotype 49,XXXYY forms two Barr bodies.

9. The paternal X is always inactivated for dosage compensation in placental mammals.

10. A cross between a tetraploid and a diploid member of the same species will produce offspring that can undergo sexual reproduction.

11. Females with only one X chromosome do not develop; this condition is lethal.

12. In the yeast Saccharomyces cerevisiae, suppressive petite mutants exhibit Mendelian inheritance because they result from nuclear mutations.

13. A plaque assay detects the number of bacterial auxotrophs on a plate.

14. Which of the following statements about Barr bodies is true?

15. Hfr bacterial cells exhibit high levels of gene transfer because

16. Watson and Crick used information from several individuals to construct their model of DNA. Whose X-ray diffraction studies were critical to their work?

17. In a sexually reproducing diploid species, gametes must be

18. Chrysanthemums have a haploid chromosome number of 9. How many chromosomes are found in tetraploid chrysanthemum species?

19. Which condition produced from an autosomal trisomy results in survival to adulthood?

20. What is the specific term that describes the loss of a single chromosome (2n - 1)?

21. Why would the transmission of Down syndrome resulting from a Robertsonian translocation be unaffected by the age of the mother?

22. Which of the following terms can be used to describe Down syndrome?

23. Why is it important for a retrovirus to carry its own reverse transcriptase protein instead of making it from its reverse transcriptase gene after it infects a cell?

24. Which of the following statements about DNA structure is true?

25. What is the complementary DNA sequence to a 5' ATGCTTGACTG 3'?

26. The hypothesis that gene duplication is essential to evolution is supported by the existence of

27. A child is born with Down syndrome. Analysis of his karyotype shows two number 21 chromosomes, a single number 18 chromosome, and an additional large chromosome about the size of chromosome 3. Which of the following conclusions can be drawn from the karyotype?

28. When a bacterial cell is transformed, after one round of cell division, only one of the two resulting cells contains new genetic material because

29. Leaf coloration in the four‑o'clock plant, Mirabilis jalapa, was one of the first examples of cytoplasmic inheritance. If ovules from a variegated‑leafed branch are pollinated with pollen from a variegated‑leafed branch, what phenotypes will be observed in the progeny?

30. Which human genetic disease does not exhibit cytoplasmic maternal inheritance?

31. Which human aneuploid condition does not involve a sex chromosome?

32. Which of the following statements about dosage compensation is true?

33. Which of the following crosses could produce a right‑hand coiled shell heterozygote in the snail Limnaea peregra, if the gene D, which codes for right‑hand coiled shells, is dominant to the gene d, which codes for left‑hand coiled shells?

34. Which gametes will be produced if nondisjunction occurs during the second meiotic division?

35. Which of the following statements about double fertilization is true?

36. What is a merozygote?

37. All of the following statements about bacteriophages are true except that

38. What observation did Griffith make in his experiment with Streptococcus pneumoniae?

39. What results did Avery, McLeod and McCarty obtain in their experiments with virulent bacteria?

40. What proportions of progeny would be expected from a cross between streptomycin‑sensitive mt+ and streptomycin‑resistant mt– strains of the algaChlamydomonas reinhardi?

41. How can duplications arise?

42. The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age. Which of the following errors most likely produces this condition?

43. What is transduction?

44. Which of the following statements about the difference between DNA and RNA is false?

45. Which of the following statements about maternal inheritance is true?

46. Which of the following statements about individuals with Klinefelter syndrome or Turner syndrome is false?

47. Which of the following elements is not involved in conjugation?

48. If a double-stranded sample of DNA has a base composition of 20% guanine, which of the following statements is true?

49. What is the diploid chromosome number of an individual with both Klinefelter syndrome and Down syndrome (three copies of chromosome 21)?

50. Which of the following phenotypic descriptions does not describe a mitochondrial trait?

51. What is the general term for a condition in which the chromosome number is not a multiple of a complete set?

52. Chromosomal aberrations may be characterized by all of the following except

53. Which term best describes an individual with Klinefelter syndrome?

54. The normally cultivated cotton plant is a tetraploid (52 chromosomes). How many chromosomes did the probable ancestral haploid have?

55. Why do some organisms use both sexual and asexual reproduction?

56. All of the following are mechanisms by which sex can be determined except

57. Which of the following statements best describes lysogeny?

58. How is genetic information transferred during conjugation?

59. Which of the following syndromes is not paired with its causative chromosomal aberration?

60. The effect of Barr body formation in mammals is that

61. Which of the following statements about the Cot1/2 or half-association value of DNA fragments is true?

62. Which of the following statements about the endosymbiotic theory is false?

63. Which genetic disease is caused by a trisomy for chromosome 13?

64. What distinguishes paracentric inversions from pericentric inversions?

65. Which of the following statements about nondisjunction is false?

66. The sporophyte stage in plants

67. Bacterial cells are always haploid unless

68. Which enzyme makes DNA from an RNA template?

69. To which positions in the sugar of a deoxyribonucleotide can a phosphate be esterified?

71. How does the Y chromosome determine maleness in humans?

72. What is one explanation for the difference between the primary sex ratio and the secondary sex ratio in humans?

73. What results would be expected from a plaque assay if the dilution factor of the phage‑infected culture were too low?

74. Which of the following statements does not describe Z-DNA?

75. What conclusion could be drawn if Hershey and Chase had found only 35S in their bacterial cells?

76. Leaf coloration in the four‑o'clock plant, Mirabilis jalapa, was one of the first examples of cytoplasmic inheritance. If ovules from a white‑leafed branch are pollinated with pollen from a green‑leafed branch, what phenotypes will be observed in the progeny?

77. Which of the following statements about the roundworm C. elegans is false?

78. Which of the following statements about XYY males is true?

40. What proportions of progeny would be expected from a cross between streptomycin‑sensitive mt⁺ and streptomycin‑resistant mt^– strains of the algaChlamydomonas reinhardi?

80. Of the following DNA strands in combination with their complementary strands (forming double helices), three undergo a hyperchromic shift with a Tm of about 42C. Which one has a Tm of 52C?

104. Forty-eight plaques were counted on a plate when 0.1 ml of bacteriophage-infected bacteria from a 10⁻⁶ dilution of a 10‑ml culture was plated. The original bacteriophage density was

107. In an Hfr mating with an F⁻cell, why doesn't the recipient cell always become an Hfr or F⁺ cell?