GATE Life Sciences Mock Test - 1 - GATE Life Sciences MCQ

Let X = 2⁷³ - 2⁷² - 2⁷¹
X = (2² × 2⁷¹) - (21 × 2⁷¹) - 2⁷¹
= (4 × 2⁷¹) - (2 × 2⁷¹) - 2⁷¹
= 2⁷¹ (4 - 2 - 1)
= 2⁷¹

The radial wave function of hydrogen atom for 3s orbital is given by the relationship

Percent change in energy 

At nodal points, the wave function must have a zero value, i.e. R = 0. Therefore, 3 – (2r/ a0) + (2r2/ 9a02) = 0. This is a quadratic equation in r and gives two values of r. Hence, the number of nodes is 2.

To prevent self-fertilization, many angiosperms have developed a chemical system of self-incompatibility. The most common type is sporophytic self-incompatibility, in which the secretions of the stigmatic tissue or the transmitting tissue prevent the germination or growth of incompatible pollen. Other features of the sporophytic self–incompatibility are short pollen viability and dry stigma. A second type, gametophytic self-incompatibility, involves the inability of the gametes from the same parent plant to fuse and form a zygote or, if the zygote forms, then it fails to develop. These systems force outcrossing and maintain a wide genetic diversity.

The alkaloid colchicine inhibits the formation of mitotic spindle (inhibits polymerization of microtubules) and holds the cell in metaphase. The chromosomes and DNA undergo replication but remain with in the same cell. The nucleus does not divide. This increases the number of chromosomes sets per cell. This process leads to endopolyploidy or endomymitosis.

The enzyme alternative oxidase (AOX) constitutes part of the electron transport chain in mitochondria. It provides an alternative route for electrons passing through the electron transport chain to reduce oxygen. 'Electrons are accepted directly from cytochrome C by alternative oxidase' is incorrect.

When there is one name for two different plants, it is homonym. When species and sub species names are same, it is antonyms. When generic and specific names are same, it is called tautonyms. In case of two or more names are given, the oldest i.e. the name given first is recognized as the valid name and all other called synonyms.

Karsurin, a metabolites, obtained from Trichoxanthus roseus, is an immuno suppressant, and induces abortion. Barberin, obtained from coptis japonica, is an anti-bacterial and anti-inflammatory vincristine obtained from Catharanthus roseus and is antilukaemic. Codein obtained from papaver somniferum is an antifertility agent. Taxol obtained from Taxux sp. is used in breast and ovarian cancer treatment.

Here the recessive allele in homogenous condition marks the effect of dominant allele. For e.g. In mice, the wild body colour is known as agouti (greyish) and is controlled by gene say A which is hypostatic to recessive allele C. The dominant allele C in the presence of 'a' gives coloured mice. In the presence of dominant allele C, A gives rise to agouti. So, ccaa will be coloured and ccAA will be albino. When coloured mice (CCaa) are crossed with albino (ccAA), agouti mice (CcAa) appear in F1. Small cc mask the effect of AA and is therefore epistatic. Consequently, ccAA is albino. The ratio 9 : 3 : 3 : 1 is modified to 9 : 3 : 4. The combination ccAA is also albino due to the absence of both the dominant alleles.

PTC tasting is a dominant trait.
So, p = 0.2
As p + q = 1,
q = 1 - 0.2 = 0.8, q² = (0.8)² = 0.64
So, 1000 × 0.64 = 640 individuals

Geological time scale shows the ages of various eras and periods together with the major groups of plants and animals that are believed to have existed during that period. It has been divided into 6 major era. An era may be further divided into periods and periods into epoch. Mesozoic era is divided into 3 period namely cretaceous, jurassic and triassic. First bird archaeopteryx appeared in jurassic period. Archaeopteryx is a link between reptile and bird, having reptilian long tail, teeth and avian feathers and beak. In cretaceous period, the first modern bird appeared and the previous archaeopteryx became extinct.

Wuchereria bancroftii passes its life cycle in 2 hosts: man (definitive host) and mosquito (intermediate host). The embryonic stage of Wuchereria bancroftii is known as microfilariae. Sheathed microfilariae are ingested by the mosquito during its blood meal. They cast off the sheath quickly, penetrate the gut wall within an hour or two, and migrate to the thoracic muscle. Here they rest and begin to metamorphose. Within 2 weeks, the microfilariae develop into infective larvae inside the mosquito thoracic muscle through 3 larval stages. The infective stage of microfilariae then enters the proboscis sheath of mosquito.

Down syndrome (21 trisomy) is a condition in which a person is born with an extra copy of chromosome 21. People with Down syndrome can have physical problems, as well as intellectual disabilities. Every person born with Down syndrome is different.
Cri-du-chat syndrome (5p-) is a group of symptoms that result from missing a piece of chromosome number 5. The syndrome's name is based on the infant's cry, which is high-pitched and sounds like a cat.
Klinefelter syndrome (47, XXY) is a condition that occurs in men who have an extra X chromosome in most of their cells. The most common symptom is infertility. Teenagers with Klinefelter syndrome may have less facial and body hair and may be less muscular than other boys.
Turner syndrome (45, X) is a genetic disorder that affects a girl's development. The cause is a missing or incomplete X chromosome. Most women with Turner syndrome are infertile. They are at risk for health difficulties such as high blood pressure, kidney problems, diabetes, cataract, osteoporosis and thyroid problems.

There are two main groups of cyclins:
G₁/S cyclins – essential for the control of the cell cycle at the, G₁/ S transition
Cyclin A/CDK2 – active in S phase.
Cyclin D/CDK4, Cyclin D/ CDK6 and Cyclin E/ CDK2 – regulates transition from G₁ to S phase.
G₂/M cyclins – essential for the control of the cell cycle at the G₂/M transition. G₂/M cyclins accumulate steadily during G₂ and are abruptly destroyed as cells exit from mitosis (at the end of the M phase)
Cyclin B/CDK1 – regulates progression from G₂ to M phase.
Thus, cyclin B functions during M phase in cell cycle.

Bacterial chemotaxis is the most widely studied two component sensory system. Chemotaxis is the cell's response to a stress environment. It is controlled by more than 40 genes in over 14 operons that produce proteins for the structural components of the flagella, the flagellar motor, transmembrane receptors, and signal transduction. In a typical two component system, a receptor protein transduces environmental signals into metabolic changes though phosyphorylation of a second protein. The signal cascade requires the transfer of a phosphate group from an autophosphorylating protein kinase to a regulator protein. In bacterial chemotaxis, transmembrane chemoreceptors, the CheA histidine kinase, and the CheW coupling protein assembles into signalling complexes that allow bacteria to modulate their swimming behaviour in response to environmental stimuli. The rate of autophosphorylation of the protein CheA is controlled by the transmembrane receptor proteins. CheA then in turn transfers the phosphate group at aspartate residues to another protein, CheY, which interacts directly with the flagellar switch to affect a change in swimming pattern.

Oxidation of glyceraldehyde - 3 - phosphate to 1, 3 - bisphosphoglycerate is catalysed by glyceraldehyde - 3 - phosphate dehydrogenase. The aldehyde group of glyceraldehyde - 3 - phosphate first reacts with the – SH group of an essential Cys residue in the active site of the enzyme. Iodoacetate reacts with the – SH group of Cys residue in glyceraldehyde - 3 - phosphate dehydrogenase. Hence, iodoacetate is a potent inhibitor of glyceraldehyde - 3 - phosphate dehydrogenase.