General Science Mixed Quiz: Set 102

On meeting an antigen a B lymphocyte multiplies and turns into a plasma cell, which pours out antibodies, that is immunoglobulins, into the blood; this arm of the defence is called humoral immunity, while T lymphocytes kill infected cells and regulate the response in cell-mediated immunity.

Meiosis makes gametes that differ from one another, and fertilization joins a gamete from each of two parents, so every offspring gets a new mix of genes.

The British geneticist Alec Jeffreys developed DNA fingerprinting in 1984 by studying short repeated sequences that vary in number from person to person, and the method is now used in criminal investigation, in disputes about parentage and in identifying victims of accidents and disasters.

Above the threshold, the kinetic energy of the ejected electrons rises as the frequency of the light rises, so the statement that it does not change is wrong.

Sound is a mechanical wave that needs a medium to travel, while the other three are electromagnetic waves. Sound travels as a longitudinal wave of compressions and rarefactions in air, water or solids, which is why it cannot pass through a vacuum.

The genes called cry genes are taken from Bacillus thuringiensis, a bacterium of the soil that forms protein crystals during its spore stage.

The antibodies, mainly of the IgA class, come ready-made in the first milk, the colostrum, and the child's own immune system does no work, which is why the protection begins at once and lasts only a few months; antibodies of the IgG class reach the foetus through the placenta in…

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

In 1983 the American company Eli Lilly put the DNA sequences of the A and B chains of human insulin into Escherichia coli, produced the two chains separately and joined them by disulphide bonds to make a hormone identical to the human one; it was sold as Humulin, the first…

This is the incorrect statement, because periodic motion repeats after every interval T, again and again. The time period T of a pendulum is the time for one complete oscillation, that is, the smallest interval after which the bob returns to the same position moving in the same direction.

The correct answer is B, the oral polio vaccine, which contains live poliovirus weakened so that it can multiply in the gut and raise immunity without causing the disease; it is the vaccine given as two drops in the pulse polio rounds.

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

The deficiency of adenosine deaminase destroys the immune system because the enzyme is needed for the normal working of lymphocytes, and in 1990 lymphocytes of a girl with this disorder were grown outside the body, given a functional gene and returned to her blood; since those cells are not permanent…

The stapedius, only about 1 millimetre long, is the smallest skeletal muscle in the human body. It lies in the middle ear and is attached to the stapes, which is itself the smallest bone of the body.

These are the organs in which lymphocytes are produced and in which they mature into cells able to tell self from non-self; the B cells complete this training in the bone marrow and the T cells in the thymus, a gland behind the breastbone that shrinks with age.

Jupiter is a planet; it does not make its own light and shines only by reflecting sunlight. A luminous object produces light of its own, as stars do by nuclear fusion in their cores, where hydrogen is turned into helium.

This committee works under the Ministry of Environment, Forest and Climate Change and appraises proposals for the large scale use and the environmental release of genetically engineered organisms and products, so no transgenic crop may be grown commercially without its clearance.

The system comes from a defence mechanism of bacteria against viruses: a guide RNA takes the Cas9 protein to a chosen sequence in the DNA, Cas9 cuts both strands there, and the cell's own repair machinery then changes the sequence, so a gene can be switched off or corrected in…

A small piece of tissue called an explant is placed in a sterile nutrient medium with growth regulators, it forms an unorganised mass called a callus and then whole plantlets, because a plant cell is totipotent, that is, able to give rise to a complete plant; the plants so raised…

The order is plasmid (1952), DNA double helix (1953), DNA fingerprinting (1984) and the cloning of Dolly (1996). Joshua Lederberg coined the word "plasmid" in 1952 for genetic material that lives outside the chromosome; plasmids later became the main vectors of genetic engineering.