Biology Test - 4 (Medical Entrance)

Episome is a genetic determinant (as the DNA of some bacteriophages) that can replicate autonomously in bacterial cytoplasm or as an integral part of the chromosomes.

Cybrids are formed by fusion of cytoplasms only.

This option is correct because rubredoxin is a small iron-sulphur protein found in various sulphur-metabolising bacteria.

Ferulic acid causes dormancy of seeds.

Besides being selectively permeable, plasma membrane of eukaryotes also functions in synthesis of ATP through chemiosmosis.

A variable number tandem repeat (VNTR) is a location in a genome where a short nucleotide sequence is organised as a tandem repeat.

It is the largest cartilage. It is broad and C-shaped in outline, with a V-shaped notch on the superior edge.
There are two small elongated club-shaped nodules of elastic fibro cartilage which lie above and anterior to corniculate cartilage.

The dinoflagellates causing red tides are known as Gonyaulax, which contain a neurotoxin and are poisonous to marine fauna.

Ectomycorrhiza forms between fungi and the roots of around 2% of plant species. These tend to be composed of woody plants, including species from the birch, dipterocarp, myrtle, beech, willow, pine and rose families. Most plants form with endomycorrhizae.

Barochory or the plant use of gravity for dispersal is a simple means of achieving seed dispersal. The effect of gravity on heavier fruits causes them to fall from the plant when ripe. Fruits exhibiting this type of dispersal include apples, coconuts and passion fruit, and those with harder shells.

A gene whose expression allows one to identify cells that have been transformed or transfected with a vector containing the marker gene is known as a selectable marker which helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants.
Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc. are considered as useful selectable markers for Escherichia coli.
Hence, the set ‘ampicillin, chloramphenicol, tetracycline’ represents selectable marker for Escherichia coli.

Peacocks possess very colorful and elaborate plumage to attract females. Thus, they exhibit Fisherian runaway mechanism.

Impaction is a fracture in which the bones involved are driven into each other.

Volvox form spherical colonies up to 50,000 cells in number. The colonies live in fresh water habitat.

This placentation involves the presence of multicarpellary, syncarpous and unilocular gynoecium. The ovules are borne on a central column arising from the base. For example, Portulacaceae and Primulaceae.

In the small intestine, Paneth cells residing at the bottom of the intestinal crypts are the key effectors of innate mucosal defense.

This is due to low food calorie intake not due to protein deficiency. In developing countries like India, it is common in infants below one year of age. The causal factor may be due to early replacement of mother's milk by other foods of low protein and calorific value. This may happen if the mother has a second pregnancy when the older infant is still too young.

This is true. The cleavage in the fertilised egg of humans starts when the egg is in fallopian tube.

In the developing embryos of mammals, the cardiogenic region lies cranial to the prochordal plate and its descendant, the oropharyngeal membrane. The heart tubes form on the endoderm side of intraembryonic coelom in the cardiogenic region. Following the head and lateral body folding, heart and its portion of intraembryonic coelom called pericardial cavity lie in the chest.

Human infants do not absorb oral IgA from colostrum or milk, unlike lamb.

The concentration of heavy metals in the body of the organisms increases with the increase in trophic level. Since phytoplanktons are present at the lowermost trophic level, the concentration of heavy metals in phytoplanktons will be the minimum, while the concentration of heavy metals in herring gull will be the highest as it is present at the highest trophic level. Hence, the correct order of organisms with increasing levels of heavy metals is Phytoplankton < Zooplankton < Smelt < Lake trout < Herring gull.

Roots in some genera of gymnosperm have fungal association in the form of mycorrhiza (Pinus) while in some others (Cycas), small specialised roots called coralloid roots are associated with nitrogen fixing cyanobacteria, i.e. cycas.

tRNAs are short-chain RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesised at the ribosome of the cell (according to directions coded in the mRNA). It is also called soluble RNA because it is too small to be precipitated by ultracentrifugation at 100,000 g. It constitutes about 10-20% of the total RNA of the cell. Transfer RNA is a relatively small RNA having a molecular weight of about 25,000 to 30,000 and the sedimentation coefficient of mature eukaryote tRNA is 3.8S.

A hypostatic gene is a gene whose phenotype is altered or suppressed.

These are bone-like or columnar with swollen ends. For example: Sub-epidermal covering of legume seeds.

The tendrils develop from the apex of the developing leaf, as in Gloriosa. This type of leaf apex is known as the cirrhose.

This area is a biodiversity hotspot in India.

Euhrychiopsis lecontei and its assumed keystone effects on aquatic plant species diversify by foraging on nuisance Eurasian Watermilfoil.

This is the correct option. The ABO blood group system in humans is controlled by two dominant and one recessive alleles.

Phytoremediation is the use of living green plants for in situ risk reduction and/or removal of contaminants from contaminated soil, water, sediments, etc.