Biology Test - 58

Human insulin is being commercially produced from a transgenic species of Escherichia. In 1983, Eli Lilly an American company, first prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of Escherichia coil to produce insulin and chains. 

Embryo of flowering plant is always Diploid (2n).

The plant life cycle alternates between haploid and diploid generations. Embryonic development is seen only in the diploid generation. The embryo, however, is produced by the fusion of gametes, which are formed only by the haploid generation.

Properties of field horsetail are:

• They are non-photosynthetic.
• They are unbranched.

Field horsetail (Equisetum arvense) and scouringrush  are common perennial weeds found in wet soils. While these are just a few of the cone-bearing plants, there are many others.

The figure given in option (b) represents the free central placentation. In free central placentation, ovary is unilocular and ovules are borne on the axis in the center of the ovary and septa are absent. It is seen in Dianthus and Primrose.

Functional residual volume is after normal inspiration. Functional residual capacity (FRC), is the volume remaining in the lungs after a normal, passive exhalation. In a normal individual, this is about 3L. The FRC also represents the point of the breathing cycle where the lung tissue elastic recoil and chest wall outward expansion is balanced and equal.

Lac operon is made up of one regulator, one operator and three structural genes. The three structural genes are LacZ, LacY and LacA. LacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. LacY encodes beta permease which pumps the lactose inside the cell. Lac A encodes beta transacetylase which removes toxic substances from the cell.The regulator gene produces m-RNA which translates into the repressor. The repressor attaches to the operator and blocks the expression of the structural gene in absence of inducer. In presence of inducer, the repressor attaches to the inducer and operator is not blocked so it allows the expression of the structural gene. Operator genes are a region of DNA sequence which attaches to the repressor molecule and stops the expression of the structural gene. So, the correct answer is option C.

Bainbridge reflux causes increases heart rate.

Bainbridge Reflex:

• Positive feedback mechanism with compensatory increase in heart rate – Due to rise in right atrial pressure.
• Commonly referred to as “atrial reflex”.
• Resulting from increased blood pressure or increased distension of large systemic veins & right upper chamber of heart.

Slow conduction velocity is seen with postganglionic autonomic nerve fibers.

Erlanger & Gasser classification: 

C fiber – Characteristics: 

• Diameter – 0.2-1.0 
• Myelination – Unmyelinated 
• Conduction – 0.2-2 (minimum) 

Functions: 

• Pain – Slow pain (“Protopathic /Second pain) 
• Temperature 
• Pressure 
• Postganglionic autonomic fibers. 
• High susceptibility to: Local anesthetics

Adenosine deaminase deficiency can be permanently cured by gene therapy at early embryonic stages. This deficiency can be treated by bone marrow transplantation, or by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But permanent treatment can be done by introduction of gene isolated from bone marrow cells, which produces ADA, into the cells of the patient at early embryonic stage.

Fruit is a modification of Ovary.

Botanically, a fruit is a mature ovary and its associated parts. Fertilization induces various changes in a flower: the anthers and stigma wither, the petals drop off, and the sepals may be shed or undergo modifications; the ovary enlarges, and the ovules develop into seeds, each containing an embryo plant.