DNA Biotechnology Sample Questions

Northern blot analysis is a laboratory technique used to detect and analyze RNA molecules. It involves the separation of RNA molecules based on their size using gel electrophoresis and then transferring them onto a membrane. The transferred RNA molecules are then hybridized with a complementary labeled probe, allowing for the detection and analysis of specific RNA molecules. Therefore, the correct answer is "Detects RNA molecules."

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.

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.

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.

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.

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.

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.

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.