Genetics Exam II
Years and years ago, if somebody had a chance of developing a life-threatening illness as a result of their previous generations suffering from it, they’d have to roll the dice and hope for the best until the day that they start developing symptoms. These days, however, we have a wonderful thing called genetics, a branch of biological study which allows us to find out early on! What do you know about this study?
- 1.
What observation did Griffith make in his experiment with Streptococcus pneumoniae?
- A.
The mouse survived injection of live virulent (smooth) Streptococcus pneumoniae.
- B.
That DNA is the genetic material.
- C.
The mouse did not survive when injected with a mixture of live, avirulent (smooth) Streptococcus pneumoniae and heat-killed virulent Streptococcus pneumoniae.
- D.
The heat-killed, virulent Streptococcus pneumoniae was lethal to the mouse.
Correct Answer
C. The mouse did not survive when injected with a mixture of live, avirulent (smooth) Streptococcus pneumoniae and heat-killed virulent Streptococcus pneumoniae. -
- 2.
What results did Avery, McLeod and McCarty obtain in their experiments with virulent bacteria?
- A.
Protease destroyed the transforming activity.
- B.
DNase destroyed the transforming activity.
- C.
RNase destroyed the transforming activity.
- D.
The transforming principle was too complex and difficult to be purified.
Correct Answer
B. DNase destroyed the transforming activity. -
- 3.
Which enzyme makes DNA from an RNA template?
- A.
RNA polymerase
- B.
DNA polymerase
- C.
Reverse Transcriptase
- D.
Replicase
Correct Answer
C. Reverse Transcriptase -
- 4.
In forming a nucleotide, phosphorus is most often attached to the nucleoside at the C-5' position of the sugar.
- A.
True
- B.
False
Correct Answer
A. True -
- 5.
Which of the following is true of thymine?
- A.
Thymine can never be attached to ribose.
- B.
Thymine is the same as 5-methyl uracil.
- C.
Thymine has an amino group at the C-4 position.
- D.
Thymine has a methyl group attached to the N-1 position.
Correct Answer
B. Thymine is the same as 5-methyl uracil. -
- 6.
Watson and Crick used information from several individuals to construct their model of DNA. Whose X-ray diffraction studies were critical to their work?
- A.
Linus Pauling
- B.
Phoebus Levene
- C.
Maurice Wilkins
- D.
Rosalind Franklin
Correct Answer
D. Rosalind Franklin -
- 7.
If a double-stranded sample of DNA has a base composition of 20% guanine, which of the following statements is true?
- A.
The amount of the other purine adenine must also equal 20%.
- B.
The amount of cytosine must be equal to 30% so that the total amount of G + C equals 50%.
- C.
The amount of thymine must equal 30%.
- D.
The ratio of purines to pyrimiidines must be greater than 1.
Correct Answer
C. The amount of thymine must equal 30%. -
- 8.
Which of the following statements does not describe Z-DNA?
- A.
The sugar phosphate backbone of Z-DNA assumes a zigzag course through space.
- B.
Z-DNA is a typical of GC-rich sequences.
- C.
It forms a left-handed helix.
- D.
The strands are not antiparallel.
Correct Answer
D. The strands are not antiparallel. -
- 9.
RNA differs from DNA in all of the following ways except by
- A.
The sugar molecule.
- B.
The 5'-3' orientation of the polynucleotide strand.
- C.
The presence of uracil.
- D.
The number of different functions performed.
Correct Answer
B. The 5'-3' orientation of the polynucleotide strand. -
- 10.
Of the following DNA strands in combination with their complementary strands (forming double helices), three undergo a hyperchromic shift with a Tm of about 42*C. Which one has a Tm of 52*C?
- A.
ATTGAGTGTA
- B.
CTTAAATTTG
- C.
AAATTTGGGA
- D.
TCATGCGATC
Correct Answer
D. TCATGCGATC -
- 11.
Which technique can be used to identify the location of genes on a chromosome?
- A.
FISH
- B.
X-ray diffraction analysis
- C.
Reassociation kinetics
- D.
Electrophoresis
Correct Answer
A. FISH -
- 12.
Which of the following statements about the Cot1/2 or half-association value of DNA fragments is true?
- A.
A longer DNA molecule would associate more quickly (smaller Cot1/2 value).
- B.
Molecules with the highest GC content would associate more slowly.
- C.
DNA with more repeated sequences requires more time to reassociate (smaller Cot value).
- D.
Shorter DNA molecules would associate more quickly (smaller Cot1/2 values).
Correct Answer
D. Shorter DNA molecules would associate more quickly (smaller Cot1/2 values). -
- 13.
If Avery, MacLeod, and McCarty had determined that the transforming molecule was a protein, what experimental results would not have been observed?
- A.
Heat-killed cultures treated with DNase would transform the R cells.
- B.
Heat-killed cultures treated with protease would not transform the R cells.
- C.
Heat-killed cultures treated with RNase would transform the R cells.
- D.
Heat-killed cultures treated with protease would transform the R cells.
Correct Answer
C. Heat-killed cultures treated with RNase would transform the R cells. -
- 14.
What conclusion could be drawn if Hershey and Chase had found only 35S in their bacterial cells?
- A.
No conclusion is possible.
- B.
DNA and protein together serve as the genetic material.
- C.
DNA is the genetic material.
- D.
Protein is the genetic material.
Correct Answer
D. Protein is the genetic material. -
- 15.
To which positions in the sugar of a deoxyribonucleotide can a phosphate be esterified?
- A.
C-3' and C-5'
- B.
C-5'
- C.
C-1', C-2', and C-3'
- D.
C-1' and C-5'
Correct Answer
A. C-3' and C-5' -
- 16.
Which of the following statements best describes the structure of a DNA molecule?
- A.
DNA is composed of a sugar-phosphate backbone with bases projecting toward the inside of the backbone.
- B.
DNA is composed of a sugar-phosphate backbone with bases projecting toward the outside of the backbone.
- C.
DNA is composed of a sugar-phosphate backbone made up of bases hydrogen-bonded to each other.
- D.
DNA is composed of a deoxynucleoside triphosphate with a base attached to it.
Correct Answer
A. DNA is composed of a sugar-phosphate backbone with bases projecting toward the inside of the backbone. -
- 17.
If two DNA strands of identical length were analyzed, which of the following statements would be true of their Tm or melting temperature?
- A.
DNA with a low AT content would melt more slowly.
- B.
All DNA strands of equal length have equal melting temperatures.
- C.
The DNA with the greater number of repetitive sequences will melt more slowly (lower Tm).
- D.
DNA with a high GC content must have a lower Tm.
Correct Answer
A. DNA with a low AT content would melt more slowly. -
- 18.
Which of the following statements about the difference between DNA and RNA is false?
- A.
RNA is usually much longer than DNA.
- B.
DNA is usually double-stranded.
- C.
RNA has a free 2' hydroxyl group.
- D.
The DNA base composition must have the amount of purines equal to the amount of pyrimidines.
Correct Answer
A. RNA is usually much longer than DNA. -
- 19.
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?
- A.
It is not important; the virus can make its own reverse transcriptase from its viral RNA after infection.
- B.
The viral reverse transcriptase is different from the host cell's reverse transcriptase.
- C.
The retrovirus must make DNA before it can use the cell's molecular machinery to make reverse transcriptase. Normal cells do not contain reverse transcriptase.
Correct Answer
C. The retrovirus must make DNA before it can use the cell's molecular machinery to make reverse transcriptase. Normal cells do not contain reverse transcriptase. -
- 20.
Guanine and adenine are purines found in DNA.
- A.
True
- B.
False
Correct Answer
A. True -
- 21.
Which of the following statements about DNA structure is true?
- A.
The pentose sugar in DNA is ribose.
- B.
Nucleic acids are formed through phosphodiester bonds that link nucleosides together.
- C.
Hydrogen bonds formed between the sugar-phosphate backbone of the two DNA chains help to stabilize DNA structure.
- D.
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
Correct Answer
D. The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions. -
- 22.
What is the complementary DNA sequence to a 5' ATGCTTGACTG 3'?
- A.
5' TACGAACTGAC 3'
- B.
5' CAGTCAAGCAT 3'
- C.
5' ATGCTTGACTG 3'
- D.
5' ACTCTACGTAG 3'
Correct Answer
B. 5' CAGTCAAGCAT 3' -
- 23.
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?
- A.
All white‑leafed progeny
- B.
White‑ and green‑leafed progeny
- C.
All variegated‑leafed progeny
- D.
All green‑leafed progeny
Correct Answer
A. All white‑leafed progeny -
- 24.
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?
- A.
All white‑leafed progeny
- B.
White‑ and green‑leafed progeny
- C.
All variegated‑leafed progeny
- D.
All green‑leafed progeny
Correct Answer
C. All variegated‑leafed progeny -
- 25.
In the yeast Saccharomyces cerevisiae, suppressive petite mutants exhibit Mendelian inheritance because they result from nuclear mutations.
- A.
True
- B.
False
Correct Answer
B. False -
- 26.
Which of the following statements about the endosymbiotic theory is false?
- A.
Mitochondria and chloroplasts arose independently from free‑living bacteria.
- B.
The ancestral bacteria from which mitochondria and chloroplasts are derived were capable of photosynthesis and aerobic respiration.
- C.
The entire genome of the ancestral bacteria has been preserved in present‑day mitochondria and chloroplasts.
- D.
Eukaryotic cells engulfed the ancestral bacteria from which mitochondria and chloroplasts are derived, and the two entities formed a symbiotic relationship.
Correct Answer
C. The entire genome of the ancestral bacteria has been preserved in present‑day mitochondria and chloroplasts. -
- 27.
Which term describes the condition in which cells have a variable mixture of organelles with different genetic origins?
- A.
Heteroduplex
- B.
Heteroplasmy
- C.
Heterokaryon
- D.
Heterozygous
Correct Answer
B. Heteroplasmy -
- 28.
Which human genetic disease does not exhibit cytoplasmic maternal inheritance?
- A.
Kearns-Sayre syndrome
- B.
Leber's hereditary optic neuropathy
- C.
Hemophilia
- D.
Myoclonic epilepsy
Correct Answer
C. Hemophilia -
- 29.
Which of the following is an example of infectious heredity?
- A.
Petite mutations in Saccharomyces cerevisiae
- B.
Shell coiling in Limnaea peregra
- C.
Variegation in Mirabilis jalapa
- D.
High female sex ratio in Drosophila bifasciata and Drosophila willistoni
Correct Answer
D. High female sex ratio in Drosophila bifasciata and Drosophila willistoni -
- 30.
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?
- A.
It is a sex-influenced trait.
- B.
The trait is an example of maternal inheritance.
- C.
It is an X-linked trait.
- D.
The trait is an example of maternal influence.
Correct Answer
D. The trait is an example of maternal influence. -
- 31.
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?
- A.
Left‑hand coiled Dd female × left‑hand coiled dd male
- B.
Left‑hand coiled DD female × left‑hand coiled dd male
- C.
Right‑hand coiled dd female × left‑hand coiled DD male
- D.
Left‑hand coiled DD female × right‑hand coiled dd male
Correct Answer
C. Right‑hand coiled dd female × left‑hand coiled DD male -
- 32.
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?
- A.
Left‑hand coiled DD female × right‑hand coiled DD male
- B.
Right‑hand coiled dd female × right‑hand coiled dd male
- C.
Left‑hand coiled dd female × right‑hand coiled DD male
- D.
Right‑hand coiled Dd female × right‑hand coiled Dd male
Correct Answer
D. Right‑hand coiled Dd female × right‑hand coiled Dd male -
- 33.
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.
- A.
True
- B.
False
Correct Answer
A. True -
- 34.
Which of the following phenotypic descriptions does not describe a mitochondrial trait?
- A.
Petite in Saccharomyces cerevisiae
- B.
Kearns–Sayre syndrome in humans
- C.
Poky in Neurospora crassa
- D.
Streptomycin resistance in Chlamydomonas reinhardi
Correct Answer
D. Streptomycin resistance in Chlamydomonas reinhardi -
- 35.
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?
- A.
The mother was heterozygous, and the gamete that formed the zygote did not carry the mutant allele.
- B.
The mother exhibited incomplete penetrance for the trait.
- C.
The disease does not affect females, only males.
- D.
A new mutation arose in the mitochondrial genome.
Correct Answer
D. A new mutation arose in the mitochondrial genome. -
- 36.
What proportions of progeny would be expected from a cross between streptomycin‑sensitive mt+ and streptomycin‑resistant mt– strains of the algaChlamydomonas reinhardi?
- A.
All streptomycin‑sensitive mt+
- B.
All streptomycin‑resistant mt–
- C.
One‑half streptomycin‑resistant mt+ and one‑half streptomycin‑resistant mt–
- D.
One‑half streptomycin‑sensitive mt+and one‑half streptomycin‑sensitive mt–
Correct Answer
D. One‑half streptomycin‑sensitive mt+and one‑half streptomycin‑sensitive mt– -
- 37.
Which of the following statements about maternal inheritance is true?
- A.
In maternal inheritance, the phenotype of the progeny does not necessarily depend on the individual's genotype but on the genotype of the maternal parent.
- B.
In maternal inheritance, reciprocal crosses give identical results but with different ratios among male and female progeny.
- C.
In maternal inheritance, the genes are linked to the X chromosome.
- D.
In maternal inheritance, a trait is transmitted through the ooplasm, because the mitochondria and chloroplasts of the zygote derive from the ooplasm.
Correct Answer
D. In maternal inheritance, a trait is transmitted through the ooplasm, because the mitochondria and chloroplasts of the zygote derive from the ooplasm. -
- 38.
What is the general term for a condition in which the chromosome number is not a multiple of a complete set?
- A.
Triploidy
- B.
Aneuploidy
- C.
Polyploidy
- D.
Trisomy
Correct Answer
B. Aneuploidy -
- 39.
Which gametes will be produced if nondisjunction occurs during the second meiotic division?
- A.
All haploid gametes
- B.
Two haploid gametes, one diploid gamete, and one gamete missing a copy of one of the chromosomes
- C.
Two diploid gametes and two haploid gametes
- D.
All trisomic gametes
Correct Answer
B. Two haploid gametes, one diploid gamete, and one gamete missing a copy of one of the chromosomes -
- 40.
What is the specific term that describes the loss of a single chromosome (2n - 1)?
- A.
Monosomy
- B.
Trisomy
- C.
Aneuploidy
- D.
Monoploidy
Correct Answer
A. Monosomy -
- 41.
Which genetic disease is caused by a trisomy for chromosome 13?
- A.
Cri-du-chat syndrome
- B.
Edwards syndrome
- C.
Down syndrome
- D.
Patau syndrome
Correct Answer
D. Patau syndrome -
- 42.
Which human chromosomes have been observed in an aneuploid condition in fetuses?
- A.
Chromosomes 21, 18, and 13
- B.
Only the sex chromosomes X and Y
- C.
X, Y, and chromosome 21
- D.
All chromosomes
Correct Answer
D. All chromosomes -
- 43.
Which term specifically refers to the gain of extra chromosome sets from individuals of the same species?
- A.
Allopolyploidy
- B.
Autopolyploidy
- C.
Euploidy
- D.
Triploidy
Correct Answer
B. Autopolyploidy -
- 44.
Chromosomal aberrations may be characterized by all of the following except
- A.
Chromosome loss
- B.
Translocations
- C.
Frameshift mutations
- D.
Inversions
Correct Answer
C. Frameshift mutations -
- 45.
The hypothesis that gene duplication is essential to evolution is supported by the existence of
- A.
Fragile sites.
- B.
Gene families.
- C.
Intercalary deletions.
- D.
Inversions.
Correct Answer
B. Gene families. -
- 46.
Which of the following human genetic diseases is caused by a segmental deletion (partial monosomy)?
- A.
Fragile X syndrome
- B.
Turner syndrome
- C.
Cri-du-chat syndrome
- D.
Edwards syndrome
Correct Answer
C. Cri-du-chat syndrome -
- 47.
What distinguishes paracentric inversions from pericentric inversions?
- A.
Inclusion of the centromere in the inversion.
- B.
One suppresses crossovers; the other encourages crossovers.
- C.
The placement of the centromere in the inversion.
- D.
The formation of dicentric bridges.
Correct Answer
A. Inclusion of the centromere in the inversion. -
- 48.
Why would the transmission of Down syndrome resulting from a Robertsonian translocation be unaffected by the age of the mother?
- A.
Down syndrome resulting from a Robertsonian translocation does not result from nondisjunction, which is affected by age.
- B.
This statement is incorrect; the age of the mother does affect the transmission of Down syndrome resulting from Robertsonian translocations.
- C.
Mothers with a Robertsonian translocation never have children.
- D.
Robertsonian translocations occur only in young mothers.
Correct Answer
A. Down syndrome resulting from a Robertsonian translocation does not result from nondisjunction, which is affected by age. -
- 49.
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.
- A.
True
- B.
False
Correct Answer
A. True -
- 50.
Which of the following statements about nondisjunction is false?
- A.
It separates maternal from paternal chromatids.
- B.
It occurs more frequently in human females over age 35.
- C.
It may fail to separate maternal chromatids from one another or paternal chromatids from one another.
- D.
It may fail to separate maternal from paternal chromatids.
Correct Answer
A. It separates maternal from paternal chromatids. -
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