Genetics & Developmental Biology

Genetics & Developmental Biology

The term “Molecular scissors” refers to:

Restriction endonucleases recognize specific palindromic sequences and cut phosphodiester bonds producing fragments. Their precision in cutting at defined sites earned them the nickname molecular scissors. Taq polymerase synthesizes DNA, while palindromes are recognition substrates.

Ref: Watson J.D. et al., Molecular Biology of the Gene, 7th Edition, Chapter 4, describes restriction enzymes as molecular scissors that recognize palindromic sequences and cut DNA at specific sites for cloning, published by Pearson Education.

View Details

Genetics & Developmental Biology

In recombinant DNA technology, the term vector refers to:

In cloning, vector carries foreign DNA into host cells for replication and expression. Typical plasmid vector includes origin of replication, selectable marker, and multiple cloning site. It replicates autonomously, maintaining insert. Restriction enzymes are molecular scissors, not vectors.

Ref: Primrose S.B. and Twyman R.M., Principles of Gene Manipulation and Genomics, 8th Edition, Chapter 4, defines vector as plasmid used to transfer foreign DNA into living host cell containing origin, marker, and cloning site, published by Blackwell Publishing.

View Details

Genetics & Developmental Biology

Microinjection is a method used to:

Microinjection uses fine glass needle to deliver DNA, RNA, or proteins directly into nucleus or cytoplasm of zygotes and cultured cells. In transgenics, recombinant constructs are injected into male pronucleus before fusion, integrating randomly. This bypasses vector-mediated delivery limitations.

Ref: Watson J.D. et al., Molecular Biology of the Gene, 7th Edition, Chapter 7, defines microinjection method for introducing recombinant DNA constructs directly into animal cell nucleus or pronucleus to create transgenic organisms, published by Pearson Education.

View Details

Genetics & Developmental Biology

The mRNA codon of valine is:

Genetic code dictionary shows valine encoded by four synonymous codons differing at third base: GUU, GUC, GUA, and GUG. Each starts with GU, consistent with degeneracy and wobble. UGG encodes tryptophan, CCA proline, and TTG is not standard mRNA codon.

Ref: Nelson D.L. and Cox M.M., Lehninger Principles of Biochemistry, 7th Edition, Chapter 27, presents complete genetic code table where valine is encoded by GUG as well as GUU GUC GUA demonstrating codon degeneracy and wobble, published by W.H. Freeman.

View Details

Genetics & Developmental Biology

Insulin is produced by genetic engineering using:

Recombinant human insulin is produced by cloning A and B chain genes or proinsulin cDNA into plasmid vector expressed in Escherichia coli. Bacterial fermentation yields inclusion bodies processed and refolded to active hormone. This replaced animal insulin, avoiding immunogenicity and supply limitations.

Ref: Glick B.R. et al., Molecular Biotechnology: Principles and Applications of Recombinant DNA, 5th Edition, Chapter 21, details production of recombinant human insulin using Escherichia coli expression system with plasmid vector and fermentation processing, published by ASM Press.

View Details

Genetics & Developmental Biology

In most species, mitochondrial DNA is passed down from:

Mitochondria contain circular DNA encoding oxidative phosphorylation components, inherited almost exclusively via oocyte cytoplasm. Sperm mitochondria are typically eliminated after fertilization, leading to maternal uniparental transmission. This pattern enables mitochondrial lineage tracing and explains maternal mitochondrial disease inheritance.

Ref: Alberts B. et al., Molecular Biology of the Cell, 6th Edition, Chapter 14, explains mitochondrial DNA organization and maternal inheritance pattern due to oocyte cytoplasm contribution and elimination of sperm mitochondria in most species, published by Garland Science.

View Details

Genetics & Developmental Biology

Consider a 16-year-old person whose father (heterozygous) was stricken with Huntington's disease at age 39. Huntington's

Huntington disease shows autosomal dominant inheritance with complete penetrance but delayed onset due to CAG repeat expansion in huntingtin gene. A heterozygous father transmits mutant allele to half his children per meiosis. Thus each offspring, regardless of current age, has 50 percent risk.

Ref: Nussbaum R.L. et al., Thompson & Thompson Genetics in Medicine, 8th Edition, Chapter 7, explains autosomal dominant inheritance of Huntington disease with 50 percent recurrence risk for offspring of heterozygous affected father due to independent segregation, published by Elsevier Saunders.

View Details

Genetics & Developmental Biology

Golden rice is yellow in colour due to the presence of:

Golden Rice was engineered to express phytoene synthase from daffodil and bacterial carotene desaturase in endosperm. These enzymes drive beta-carotene biosynthesis pathway accumulating provitamin A, imparting distinctive yellow color. It addresses vitamin A deficiency, unlike riboflavin which is water soluble.

Ref: Buchanan B.B. et al., Biochemistry and Molecular Biology of Plants, 2nd Edition, Chapter 16, discusses metabolic engineering of Golden Rice endosperm to accumulate beta-carotene provitamin A causing yellow coloration to combat deficiency, published by Wiley Blackwell.

View Details

Genetics & Developmental Biology

The sticky ends of a fragmented DNA molecule are made of:

Restriction endonucleases cut palindromic DNA leaving single-stranded overhangs of one to four nucleotides. These unpaired bases can anneal via complementary base pairing to another fragment with matching overhangs, enabling recombinant ligation. Calcium salts and methyl groups do not form sticky ends.

Ref: Watson J.D. et al., Molecular Biology of the Gene, 7th Edition, Chapter 7, describes restriction enzyme cleavage producing sticky ends composed of unpaired single-stranded bases enabling complementary annealing and ligation, published by Pearson.

View Details

Genetics & Developmental Biology

A device in which large volume of living cells are cultured to get a specific product is called:

Bioreactor provides controlled conditions including pH, temperature, dissolved oxygen, and agitation for large-scale cultivation of microbes or animal cells. It enables production of vaccines, antibiotics, enzymes, and recombinant proteins. Thermocycler performs PCR, agitator only mixes.

Ref: Prescott L.M. et al., Prescott's Microbiology, 11th Edition, Chapter 42, defines bioreactor fermenter as device for large volume culture of living cells under controlled conditions to obtain specific products like antibiotics, published by McGraw Hill Education.

View Details

Genetics & Developmental Biology

Which of the following connective tissue often serves as a support framework for epithelium?

Areolar loose connective tissue contains fibroblasts, collagen, elastic fibers, and ground substance forming subepithelial lamina propria. It cushions epithelia, supplies nutrients from capillaries, and hosts immune cells. Dense tissues provide tensile strength, not delicate epithelial support.

Ref: Ross M.H. and Pawlina W., Histology: A Text and Atlas, 8th Edition, Chapter 6, details loose areolar connective tissue serving as support framework for epithelium in lamina propria with fibroblasts collagen and ground substance, published by Wolters Kluwer.

View Details

Genetics & Developmental Biology

Which of the following is known as the pacemaker of heart?

SA node located at junction of superior vena cava and right atrium spontaneously depolarizes fastest, around 70 beats per minute. Its action potentials propagate via atrial muscle to AV node, then Purkinje system. Autonomic inputs modulate rhythm, establishing SA node as natural pacemaker.

Ref: Hall J.E. and Guyton A.C., Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 10, explains cardiac conduction system with SA node sinoatrial node located at right atrium as natural pacemaker generating fastest rhythmicity, published by Elsevier.

View Details