Galactosemia is an inborn error of metabolism inherited as an autosomal recessive trait.

Evolutionary displacement of ancestral features to later stages of development in descendant organisms is called paedomorphosis.

Radial symmetry is characteristic of many sedentary (fixed) animals, e.g., coelenterate and Echinodermata.

Deletion is a type of chromosomal mutation in which a section of chromosome is lost, usually during mitosis or meiosis. Unlike some mutations, deletions are not usually reversible or correctable by a suppressor mutation.

Demineralization is caused by over-secretion of parathormone and occurs usually due to over growth of parathyroid glands.

Each protein has a specific three-dimensional structure that is maintained by hydrogen bonds. Normal protein functions require the maintenance of this structure.

The Hardy-Weinberg equation describes the relationship between allelic frequencies and genotype frequencies in successive generations of a population.

Haltere is one pair knob-like structures protruding from metathorax of dipterus flies (housefly). They are modified hind wings and vibrate rapidly during flight.

The distal end of small intestine (ileum) in rabbit is dilated into a small bulb-like sacculus rotundus which leads into the colon of large intestine. The sacculus rotundus has an iliocaecal valve which directs the chyme from ileum only into caecum, and from caecum into the colon.

Cretinism in congenital condition due to lack of thyroxine hormone secreted by thyroid gland.

Tay-Sachï؟½s is an inherited disease. It results when a child receives two defective genes, one from each parent.

IgG is the principal immunoglobulin in human serum. Because it moves across placental barrier, and is important in producing immunity in the infant prior to birth.

Ciliary glands are modified sweat glands at border of eyelids and are known as Mollï؟½s glands.

Snakes mainly respond to earth-borne sound vibrations through the quadrate, although they are also sensitive to low frequency air-borne sound vibrations.

Dietary proteins that contain all 10 essential amino acids are called complete proteins, while that dietary proteins which contain some, but not all, of the essential amino acids are called incomplete proteins. Plant proteins are considered incomplete proteins.

Bitot's spots are triangular, shiny, grey spots on the conjunctiva seen in vitamin A deficiency.

In human beings a few lethal genes are known which are associated with fatal 'Infantile amourotic idiocy' disease, and is caused by recessive allele in homozygous condition.