DNA Biotechnology Sample Questions

2.

Parental relationship between a man and infant can be best determined by the technique commonly referred to as DNA fingerprinting. Which of the following sequences is most conveniently analyzed by a DNA fingerprint?

Histocompatibility loci
Centromeres
Microsatellite tandem repeats (STRs)
Restriction enzyme sites
Single-copy sequences

Correct Answer

A. Microsatellite tandem repeats (STRs)

Explanation

DNA fingerprinting is a technique that analyzes specific regions of DNA that are highly variable among individuals, such as microsatellite tandem repeats (STRs). These regions consist of short repeated DNA sequences that vary in the number of repeats between individuals, making them useful for determining genetic relatedness. Histocompatibility loci, centromeres, restriction enzyme sites, and single-copy sequences are not as variable and therefore not as useful for DNA fingerprinting.

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3.

Which of the following statements describing restriction endonucleases is true

They always yield overhanging single-stranded ends
They recognize methylated DNA sequences
They recognize triplet repeats
They cleave both strands of duplex DNA
They always yield blunt ends

Correct Answer

A. They cleave both strands of duplex DNA

Explanation

Restriction endonucleases are enzymes that cleave both strands of duplex DNA at specific recognition sites. This means that they can cut both the top and bottom strands of the DNA molecule, resulting in a double-stranded break. This property makes restriction endonucleases useful tools in molecular biology for cutting DNA at specific sites for various applications such as cloning, gene editing, and DNA fingerprinting. The other statements given as options are not true for restriction endonucleases.

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4.

Which of the following statements correctly describes the recombinant DNA tool know as plasmids?

They are found more commonly in viruses than in bacteria
They are single-stranded circles
They sometimes enhance bacterial susceptibility to antibiotics
They sometimes enhance bacterial resistance to antibiotics
They are too small to be useful as vectors for the cloning of mammalian DNA segments

Correct Answer

A. They sometimes enhance bacterial resistance to antibiotics

Explanation

Plasmids are small, circular DNA molecules that can be found in both bacteria and viruses. They can carry genes that provide advantages to the host organism, such as antibiotic resistance. Therefore, they can sometimes enhance bacterial resistance to antibiotics. Plasmids are commonly used as vectors for the cloning of DNA segments, including mammalian DNA, making the statement that they are too small to be useful as vectors for mammalian DNA segments incorrect.

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5.

DNA fingerprinting is used for paternity testing and forensic identification of suspects. Which of the following is the most accurate description of DNA fingerprinting?

DNA can be isolated from blood, skin, or sperm and analyzed for variable patterns of restriction fragments arising from tandemly repeated sequences (microsatellites)
DNA is copied from blood, skin, or sperm RNA using reverse transcriptase and analyzed for patterns of complementary DNAs
DNA is isolated from blood, skin, or sperm and its fragment size distribution is analyzed by gel electrophorsis
DNA is isolated from blood, skin, or sperm and hybridized with probes from the HLA locus to visualize HLA gene patterns
DNA is isolated from blood, skin, or sperm, centrifuged to separate satellite DNA fractions, and analyzed by gel electrophoresis.

Correct Answer

A. DNA can be isolated from blood, skin, or sperm and analyzed for variable patterns of restriction fragments arising from tandemly repeated sequences (microsatellites)

Explanation

DNA fingerprinting involves isolating DNA from blood, skin, or sperm and analyzing it for variable patterns of restriction fragments that arise from tandemly repeated sequences, also known as microsatellites. These microsatellites are unique to each individual, making them useful for paternity testing and forensic identification of suspects. By comparing the patterns of restriction fragments, scientists can determine if two DNA samples match, providing evidence of a biological relationship or linking a suspect to a crime scene.

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6.

Sickle cell anemia is caused by a point mutation in the hemoglobin gene, resulting in the substitution of a single amino acid in the b-globin peptides of hemoglobin. This mutation is best detected by which of the following?

Isolation of DNA from red blood cells followed by polymerase chain reaction (PCR) amplification and restriction enzyme digestion.
Isolation of DNA from blood leukocytes followed by Southern blot analysis to detect globin gene exon sizes
Isolation of DNA from blood leukocytes followed by DNA sequencing of globin gene introns
Isolation of DNA from blood leukocytes followed by polymerase chain reaction (PCR) amplification and allele-specific oligonucleotide (ASO) hybridization
Western blot analysis of red blood cell extracts

Correct Answer

A. Isolation of DNA from blood leukocytes followed by polymerase chain reaction (PCR) amplification and allele-specific oligonucleotide (ASO) hybridization

Explanation

Sickle cell anemia is caused by a point mutation in the hemoglobin gene, which results in a substitution of a single amino acid in the b-globin peptides of hemoglobin. To detect this mutation, DNA isolation from blood leukocytes is necessary as they contain the genetic material required for analysis. Polymerase chain reaction (PCR) amplification is then performed to amplify the specific region of interest in the DNA. Finally, allele-specific oligonucleotide (ASO) hybridization is used to detect the specific mutation in the amplified DNA. This technique allows for the identification of the point mutation responsible for sickle cell anemia.

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7.

Sickle-cell anemia is caused by a missense mutation in codon 6 of the b-globin gene. Codon number 5 6 7 8 Normal allele CCT GAG GAG AAG Mutant allele CCT GTG GAG AAG A man with sickle-cell disease and his phenotypically normal wife request genetic testing because they are concerned about the risk for their unborn child. DNA samples from the man and the woman and from fetal cells obtained by amniocentesis are analyzed using the PCR to amplify exon 1 of the b-globin gene. Which 12-base nucleotide sequence was most likely used as a specific probe complementary to the coding strand of the sickle cell allele?

CCTCACCTCAGG
CCTGTGGAGAAG
GGACACCTCTTC
CTTCTCCACAGG

Correct Answer

A. CTTCTCCACAGG

Explanation

The correct answer is "CTTCTCCACAGG" because this sequence is complementary to the coding strand of the mutant sickle cell allele. The mutation in codon 6 of the b-globin gene changes the codon from GAG to GTG, resulting in a different amino acid being incorporated into the protein. By using a specific probe that is complementary to the mutant allele, the PCR amplification can specifically detect the presence of the sickle cell allele in the DNA samples from the man, woman, and fetal cells obtained by amniocentesis.

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8.

James K. is a Huntington disease patient who has recently been institutionalized and requires constant nursing care. His wife is unaffected, and they have a 38-year-old daughter, Delia, who has 4 children ranging in age from 8 to 15 years. Delia wishes to know whether she has inherited the disease-producing allele from her father. PCR amplification is carried out on the region containing the CAG repeat, shown below. Which of the flowing sets of primers would be used to amplify the CAG repeat in the brackets ([CAG]_n)? GAG TCC CTC AAG TCC TTC [CAG]n CAA CAG CCG CCA CCG CCG

GAGTCCCTCAAGTCCTTC and CGGCGGTGGCGGCTGTTG
CTTCCTGAACTCCCTGAG and CAACAGCCGCCACCGCCG
CTTCCTGAACTCCCTGAG and CGGCGGTGGCGGCTGTTG
GAGTCCCTCAAGTCCTTC and CAACAGCCGCCACCGCCG
GAGTCCCTCAAGTCCTTC and GTTGTCGGCGGTGGCGGC

Correct Answer

A. GAGTCCCTCAAGTCCTTC and CGGCGGTGGCGGCTGTTG

Explanation

The correct answer is GAGTCCCTCAAGTCCTTC and CGGCGGTGGCGGCTGTTG. These primers would be used to amplify the CAG repeat in the brackets ([CAG]n) during PCR amplification.

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DNA Biotechnology Sample Questions

Which of the following results is provided by northern blot analysis?

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Parental relationship between a man and infant can be best determined by the technique commonly referred to as DNA fingerprinting. Which of the following sequences is most conveniently analyzed by a DNA fingerprint?

Which of the following statements describing restriction endonucleases is true

Which of the following statements correctly describes the recombinant DNA tool know as plasmids?

DNA fingerprinting is used for paternity testing and forensic identification of suspects. Which of the following is the most accurate description of DNA fingerprinting?

Sickle cell anemia is caused by a point mutation in the hemoglobin gene, resulting in the substitution of a single amino acid in the b-globin peptides of hemoglobin. This mutation is best detected by which of the following?