Genetics & Molecular Biology

Genetics & Molecular Biology

Estimation of gamma-glutamyl transferase is useful to detect which one of the following clinical conditions?

Gamma-glutamyl transferase is induced by chronic ethanol consumption, residing on hepatobiliary membranes. Elevated serum GGT is sensitive marker for alcohol abuse and cholestasis, more specific than ALT for alcoholic liver injury screening.

Ref: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 6th Edition by Burtis and Ashwood, Chapter 33 on liver enzymes describes gamma-glutamyl transferase elevation useful for detecting alcohol abuse, Elsevier.

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Genetics & Molecular Biology

How many genes are present in human mitochondrial genome?

Human mtDNA is circular 16.5 kb molecule encoding 13 oxidative phosphorylation polypeptides, 22 tRNAs, and 2 rRNAs, totaling 37 genes. No introns exist, and inheritance maternal, crucial for mitochondrial respiration and disease.

Ref: Anderson et al., Nature 1981 sequencing human mitochondrial genome initially defined 37 genes; also explained in Alberts Molecular Biology of the Cell, 6th Edition Chapter 14 mitochondrial genome organization, Garland Science.

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Genetics & Molecular Biology

In spectral karyotyping (SKY), how many sets of FISH probes are utilized?

Spectral karyotyping uses 24 combinatorially labeled chromosome painting probes distinguishing each human chromosome uniquely via spectral signature. Sets cover 22 autosomes plus X and Y, enabling simultaneous visualization of all chromosomes to detect translocations.

Ref: Kallioniemi et al. developed SKY method; Ried and Schröck, Cytogenetics and Genome Research descriptions note SKY utilizes 24 FISH probe sets for whole genome karyotyping, Karger Publishers.

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Genetics & Molecular Biology

A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregat

Two loci with duplicate dominant epistasis produce red when at least one dominant allele exists at either gene. Only aabb genotype remains white. With dihybrid AaBb x AaBb, probability aabb is 1/16, leaving 15/16 red. Therefore phenotypic ratio becomes 15 red to 1 white.

Ref: Griffiths et al., Introduction to Genetic Analysis, 11th Edition, Chapter 4 on Gene Interaction explains duplicate genes yielding 15:1 ratio where dominant allele at either locus produces same phenotype, W H Freeman.

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Genetics & Molecular Biology

What approximate percentage of total RNA content in a cell is messenger RNA (mRNA)?

Total cellular RNA comprises predominantly rRNA about 80-85%, tRNA about 10-15%, while mRNA is scarce and heterogeneous representing only 2-5%. Despite low abundance, mRNA carries coding information essential for translating proteins.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 6 on RNA explains composition where rRNA dominates and mRNA constitutes 2 to 5 percent of total RNA, Garland Science.

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Genetics & Molecular Biology

If a double strand break (DSB) is not repaired during G1 phase of the cell cycle, what type of replication error would r

An unrepaired DSB entering S phase encounters replisome progression. The replication fork reaches broken end lacking template continuity, leading to fork collapse, single-ended DSBs, and genome instability requiring homologous recombination restart mechanisms.

Ref: Friedberg et al., DNA Repair and Mutagenesis, 2nd Edition, Chapter 16 on double-strand break repair discusses collapsed replication forks arising from unrepaired DSBs during S phase, ASM Press.

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Genetics & Molecular Biology

Which of the following is a protein modification that can initiate the degradation of the modified protein?

Polyubiquitination via E1-E2-E3 cascade tags proteins with Lys48-linked ubiquitin chains, targeting them to 26S proteasome for degradation. This regulates cell cycle and quality control, unlike lipid modifications which affect localization rather than proteolysis.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 3 on intracellular protein degradation explains ubiquitination initiating proteasomal degradation, Garland Science.

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Genetics & Molecular Biology

Which of the following techniques would be the best to quantify the amount of protein in a sample?

Bradford assay utilizes Coomassie Brilliant Blue binding to proteins shifting absorbance at 595nm, enabling spectrophotometric quantification versus standards. Unlike Southern blot for DNA or qPCR for nucleic acids, it directly measures total protein concentration colorimetrically.

Ref: Wilson and Walker, Principles and Techniques of Biochemistry and Molecular Biology, 8th Edition, Chapter 4 on protein determination describes Bradford assay for quantification using Coomassie dye, Cambridge University Press.

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Genetics & Molecular Biology

A piece of DNA was analyzed and 15% of its nucleotides were adenine. What percentage would be uracil?

DNA never contains uracil under normal conditions; uracil occurs in RNA replacing thymine. Chargaff's rules apply to adenine-thymine pairing, but uracil is absent except transient deamination errors. Hence percentage of uracil in analyzed DNA is zero.

Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 2 on Chemical Structure of DNA explains DNA bases adenine thymine guanine cytosine and absence of uracil, Pearson.

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Genetics & Molecular Biology

TAE buffer commonly used for DNA gel electrophoresis contains which of the following?

TAE stands for Tris-acetate-EDTA, buffering system of Tris base, acetic acid for pH, and EDTA chelating divalent cations inhibiting nucleases. It provides adequate conductivity for DNA migration and is preferred for large fragments and subsequent extraction.

Ref: Sambrook and Russell, Molecular Cloning: A Laboratory Manual, 4th Edition, Chapter 6 on gel electrophoresis details TAE buffer composition Tris EDTA acetic acid, Cold Spring Harbor Laboratory Press.

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Genetics & Molecular Biology

Which part of the compound microscope that helps in gathering and focusing light rays on the specimen to be viewed?

The condenser lens located below stage collects light from source and focuses it into a cone illuminating specimen. Adjusting condenser aperture controls contrast and resolution, essential for proper illumination distinct from magnification provided by objectives and eyepiece.

Ref: Prescott's Microbiology, 11th Edition by Willey, Sherwood and Woolverton, Chapter 2 on microscopy describes condenser function gathering and focusing light on specimen, McGraw-Hill Education.

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Genetics & Molecular Biology

Which cell component is stained by supravital staining in the reticulocytes?

Supravital dyes like brilliant cresyl blue precipitate residual ribosomal RNA and ribonucleoproteins in reticulocytes, forming visible reticulum. Mature erythrocytes lack this network, so staining distinguishes immature reticulocytes indicating increased erythropoiesis.

Ref: Dacie and Lewis Practical Haematology, 12th Edition by Bain et al., Chapter 2 on reticulocyte enumeration explains supravital staining of ribonucleoprotein reticulum, published by Elsevier.

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