Genetics & Evolutionary Biology

Genetics & Evolutionary Biology

During DNA replication the synthesis of the leading strand of DNA results in fragments known as:

DNA replication produces Okazaki fragments, short 100-200 bp segments synthesized discontinuously on lagging strand by DNA polymerase. Although question states leading strand, canonical Okazaki fragments characterize lagging strand. Among given options, Okazaki fragments remains the only legitimate replication intermediate.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 5 on DNA replication mechanisms, and Kornberg and Baker, DNA Replication, 2nd Edition, Chapter 3, describe Okazaki fragments as short discontinuous DNA segments synthesized on lagging strand by DNA polymerase during replication fork progression, published by Garland Science and University Science Books.

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Genetics & Evolutionary Biology

How many types of histone molecules are found in nature?

Chromatin contains five major histone types: linker H1 and core histones H2A, H2B, H3 and H4 forming octamer around which DNA wraps to form nucleosome. Variants exist but canonical classification counts five distinct families essential for nucleosome structure and gene regulation.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 4, discusses chromatin structure containing five major histone families H1, H2A, H2B, H3 and H4 forming nucleosome octamer core around which 147 bp DNA wraps, published by Garland Science.

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Genetics & Evolutionary Biology

The diagram which shows the arrangement of metaphasic chromosomes according to their position of centromere is called:

An ideogram is a schematic diagram showing chromosome morphology, including size, arm ratio and centromere position ordered haploid set. Karyogram displays actual photomicrograph arrangement from metaphase spreads, while ideogram idealizes banding pattern. Histogram and dendrogram represent unrelated data displays.

Ref: Gardner and Sutherland, Chromosome Abnormalities and Genetic Counseling, 4th Edition, Chapter 3, defines ideogram as schematic diagram of metaphase chromosomes arranged by centromere position and size, distinct from karyogram photomicrograph arrangement used in clinical cytogenetics, published by Oxford University Press.

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Genetics & Evolutionary Biology

The first clinical application of gene therapy over a 4-year-old girl was for:

In 1990, Ashanti DeSilva, a four-year-old with severe combined immunodeficiency due to adenosine deaminase deficiency, received first approved gene therapy by W. French Anderson. Ex vivo transduced autologous T cells expressing functional ADA gene restored immune function temporarily.

Ref: Anderson WF, Human Gene Therapy, Science 1992, and Friedmann and Roblin, Gene Therapy for Human Genetic Disease, discuss first clinical gene therapy trial in 1990 on 4-year-old Ashanti DeSilva with adenosine deaminase deficiency SCID using retroviral vector, published by AAAS.

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Genetics & Evolutionary Biology

Plasmids are used as cloning vectors for which of the following reasons?

Plasmids possess origin of replication allowing autonomous self-replication in bacterial hosts independent of chromosomal DNA, maintained at high copy number. This property, plus selectable markers, enables vector propagation and cloning. They do not replicate freely outside cells without host machinery.

Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 10, explains plasmids as cloning vectors due to autonomous self-replication via origin of replication in bacterial cells, enabling propagation of recombinant DNA with selectable markers, published by Pearson.

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Genetics & Evolutionary Biology

Which of the following is not a component of downstream processing?

Downstream processing includes cell separation, product recovery, purification and preservation after fermentation. Expression of recombinant protein occurs during upstream fermentation in bioreactor, not downstream. Hence expression is not considered part of downstream operations aimed at isolating pure product.

Ref: Shuler and Kargi, Bioprocess Engineering: Basic Concepts, 3rd Edition, Chapter 11, and Doran, Bioprocess Engineering Principles, 2nd Edition, define downstream processing as separation, purification and preservation steps after fermentation, excluding upstream expression phase, published by Pearson and Academic Press.

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Genetics & Evolutionary Biology

Biotechnologies consisting of the use of biological systems (bacteria) for the manufacture, transformation or degradatio

Biotechnology color code assigns white to industrial processes using microbes and enzymes for manufacturing chemicals, biofuels and biomaterials. Red denotes medical, green agricultural, blue marine, yellow food. Therefore bacterial fermentation for industrial transformation aligns with white biotechnology definition.

Ref: Frazzetto, White Biotechnology: The Industrial Revolution and Soetaert and Vandamme, Industrial Biotechnology, textbook defines white biotechnology as industrial use of bacteria and enzymes for manufacturing chemicals and fermentation processes for sustainable production, 1st Edition, Chapter 1, published by Wiley-VCH.

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Genetics & Evolutionary Biology

Suppose there is a deletion of 5 coding DNA nucleotides 234 to 238 position, which of the following is the correct way t

HGVS nomenclature requires coding DNA deletion described as c.start_enddel, using underscore between positions and del suffix, e.g., c.234_238del indicating nucleotides 234 through 238 deleted. Hyphen or del5 formats are non-compliant. Hence option A follows correct HGVS convention.

Ref: den Dunnen et al., HGVS Nomenclature for description of sequence variants, Human Mutation 2016, Journal article and Richards et al., Standards and guidelines for interpretation, describes coding DNA deletion format c.234_238del using underscore to indicate range deleted and del suffix, published by Wiley.

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Genetics & Evolutionary Biology

The polymerization of the gel used in PAGE occurs between polyacrylamide and:

Polyacrylamide gel for electrophoresis forms by polymerization of acrylamide monomers crosslinked with N,N'-methylene-bis-acrylamide initiated by APS and TEMED. Bis-acrylamide creates matrix pores whose size determines protein separation. Other named acrylamides are incorrect chemical identifiers for crosslinker.

Ref: Wilson and Walker, Principles and Techniques of Biochemistry and Molecular Biology, 8th Edition, Chapter 9, describes SDS-PAGE gel polymerization using acrylamide monomer crosslinked by N,N'-methylene-bis-acrylamide with APS and TEMED initiators forming polyacrylamide matrix for protein separation, published by Cambridge University Press.

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Genetics & Evolutionary Biology

How many fragments will be generated on the digestion of a closed circular DNA molecule with a restriction enzyme having

A circular plasmid cut at n recognition sites yields n linear fragments because each cut opens the circle; ends remain connected until all cuts separate segments. Thus six EcoRI-like sites produce six fragments, unlike linear DNA where n sites generate n+1 fragments.

Ref: Green and Sambrook, Molecular Cloning: A Laboratory Manual, 4th Edition, Chapter 6, explains restriction digestion of closed circular DNA where number of fragments equals number of recognition sites, so six sites generate six fragments unlike linear DNA, published by Cold Spring Harbor Laboratory Press.

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Genetics & Evolutionary Biology

The joints between the carpal bones are:

Intercarpal joints between carpal bones are plane synovial gliding joints permitting limited sliding movements, contributing to complex wrist flexibility. Hinge allows flexion-extension, saddle allows biaxial movement, pivot allows rotation. Gliding architecture matches flat articular facets of carpal bones.

Ref: Moore et al., Clinically Oriented Anatomy, 8th Edition, Chapter 6, classifies intercarpal joints as plane synovial gliding joints allowing limited sliding between carpal bones, contrasting with hinge, saddle and pivot joint types found elsewhere, published by Wolters Kluwer.

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Genetics & Evolutionary Biology

Ends of long bones are covered with:

Long bone epiphyses at articulating ends are covered by hyaline articular cartilage, providing low-friction, load-bearing surface and shock absorption. Blood cells originate in marrow, ligaments connect bone to bone, muscles attach via tendons, none cover epiphyseal surfaces physiologically.

Ref: Standring et al., Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd Edition, Section 5, explains long bone epiphyses covered by hyaline articular cartilage providing smooth low-friction joint surface and load distribution, published by Elsevier.

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