Biology Test 340

Turner's syndrome is characterized by a chromosomal condition in which a female is partially or completely missing an X chromosome, leading to a total chromosome number of 45 (2n = 45).

This condition results in various developmental and physical abnormalities.

Paper chromatography is an analytical method that is used to separate coloured chemicals or substances, especially pigments. This can also be used in secondary or primary colours in ink experiments. Leaf pigments of any green plants can be separated by using paper chromatography.

A chromatographic separation of the leaf pigments shows that the colour we see in leaves is due to a single pigment but due to four pigments: chlorophyll a (bright or blue green in the chromatogram), chlorophyll b (yellow green), xanthophylls (yellow) and carotenoids (yellow to yellow orange).

One of the main goals of the Human Genome Project was to identify all the approximately 20,000-25,000 genes in human DNA. This monumental task aimed at understanding the genetic basis of human development, physiology, and disease.

Ligase enzyme plays a crucial role in DNA replication by joining Okazaki fragments on the lagging strand, ensuring the continuity of the newly synthesized DNA strand.

Genetic codes are non-overlapping, meaning that each nucleotide is part of only one codon and codes for a single amino acid, ensuring specificity in protein synthesis.

The endosperm of gymnosperms is haploid. It is a pre-fertilization tissue and is equivalent to female gametophyte, hence it is haploid in nature but in angiosperms it is post-fertilization tissue and is generally triploid in nature.

The Miller-Urey experiment, conducted in 1953 by Stanley Miller under the guidance of Harold Urey, is renowned for simulating early Earth conditions. They used a mixture of gases thought to be present in the early Earth's atmosphere and passed electric sparks through it to simulate lightning. This resulted in the formation of several organic compounds, including amino acids, which are the building blocks of life. This experiment provided the first strong evidence that organic molecules needed for life could be synthesized from inorganic components under conditions thought to resemble those of early Earth.

Chordates are the animals that have notochord, a skeletal rod present at some stage in life cycle. In lower vertebrates, notochord persists throughout life while in higher vertebrates it is replaced by vertebral column in adults. Nonchordates never develop notochord, not even in embryonic stage.

Auxin is a weakly acidic hormone having an unsaturated ring structure and promotes cell elongation especially in shoots. Auxins was first isolated from human urine. Auxins like IAA and IBA have been isolated from plants. NAA and 2, 4 - D are synthetic auxins.

Statutory ban on amniocentesis (a foetal sex determination test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo) for sex-determination to legally check increasing menace of female foeticides, massive child immunisation, etc., are some programmes that merit mention in this connection