Biology: Topic-wise Test- 5 - NEET MCQ

A stamen or male reproductive organ of a flower is made up of two parts- a stalk-like filament and a knob like terminal anther. Each anther has two lobes which are attached at the back by a sterile band called connective. When both the anther lobes are present, the stamen is called bithecous (or dithecous). A dithecous anther is tetrasporangiate having four microsporangia. Each lobe has two microsporangia separated by a strip of sterile tissue. When a single anther lobe is present, the stamen is termed as monothecous

The correct option is A Epicotyl
Plumule- Shoot tip.

Radicle - Embryonic root.

A. Epicotyl- The portion of axis between the plumule and the cotyledonary node.

B. Hypocotyl- The portion of axis between the radicle and the cotyledonary node.

D. Coleoptile- Protective sheath of plumule.

So, the correct answer is 'Epicotyl'

A tumour inducing Ti plasmid of Agrobacterium tumefaciens has been modified into a cloning vector which is not pathogenic to the plants, However, it is still able to use its mechanism to deliver genes of our interest into various plants.
So, the correct answer is 'Statement 1 is correct but statement 2 is incorrect'.

Explanation: In monosporic development, only one megaspore out of the four produced from the megaspore mother cell (MMC) develops into the female gametophyte. The other three megaspores typically degenerate. Therefore, the assertion is correct. However, the reason is incorrect as it states that all four megaspores become functional, which is not the case in monosporic development.

Double fertilisation involves fusion of one male gamete with egg during Syngamy and fusion of two polar nuclei with other male gametes. So, total 5 nuclei are involved in double fertilisation.

• In apocarpous condition the ovaries must be free, though the other parts maybe fused.
• Example Oleandar. In simple words, separate carpels.

The separated DNA fragments can he visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to ultraviolet radiation (we cannot see pure DNA fragments in the visible light and without staining).

• A ladder is used in Gel electrophoresis as it helps in comparing the size of the DNA fragment.
• The fragments get separated from each other on the basis of molecular weight of the fragments.

RNA interference (RNAi) is present in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to complementary dsRNA molecules that binds and prevents translation of the mRNA.

Genetic engineering is the artificial synthesis, isolation, modification, combination, addition and repair of the genetic material (DNA) to alter the phenotype of the host organism to suit human needs. It is the manipulation of genes by man in vitro. Restriction endonucleases play major role in genetic engineering as they can cut DNA at specific sites.

A megasporangium is a minute structure attached to the placenta with the help of a stalk known as a funicle. A megasporangium is also usually known as the ovule. The ovule attaches with the funicle in a region called the hilum. Each ovule may be covered by a couple of envelopes known as integuments that surround the ovule from all around except at its tip. The opening at the tip of the ovule is called the micropyle. The end where micropyle is present is the micropylar end. Opposite to the micropylar end is a structure known as a chalaza. It represents the basal end of the ovule. The protective integuments enclose a mass of cells called nucellus. The cells of the nucellus have abundant nourishment materials. The nucellus covers the embryo sac or the female gametophyte. A meiotic division in the megaspore mother cell generally gives rise to four haploid megaspores, out of which a single functional megaspore matures into an embryo sac inside the ovule.

• A germ pore is a small pore in the fungal pore’s outer wall from which the germ tube then exits at germination. If its location is taken into consideration then it can be apical or eccentric.
• Germ pore plays an essential part in the fertilization of plants. It helps in pollen tube formation and releases the male gamete during fertilization.

CrylAb has been introduced in Bt corn to protect it from corn borer.

The groups of letters that form same words when read both forward and backward are called Palindrome. For example MALYALAM which read same from both side.

• Rop genes in pBR322 codes for protein involved in replication of plasmid.
• Plasmid are able to take the foreign gene and to be transferred to target cells.

Entomophilous flowers produce an odour which may be pleasant (e.g., jasmine) or foul (e.g., Aristolochia, Arum, Rafflesia) Foul smell attracts flies and beetles. Malacophily is the kind of pollination in which snails perform pollination e.g. in Arisaema (cobra plant). Hydrophily refers to water and anemophily refers to wind pollination.

Bt toxin is obtained from Bacillus thuringiensis bacterium that can kill certain insects like tobacco budworm, armyworm, beetles and flies.

ELISA is abbreviation of Enzyme linked immunosorbent assay. It is used to detected the disease at early stage.

• Origin of replication is the specific DNA sequence on chromosome that which is responsible for initiating replication.
• Origin of replication is essential for replication of particular DNA segment.

Endosperm is present around the growing embryo. It provides nutrition to the growing embryo. In leguminous plants, it is completely consumed by the embryo and nothing remains in seed as in pea.

Bioreactor is used to produce large scale production. Bioreactor is a large vessels in which large scale raw materials are biologically converted into specific products.

• In gel electrophoresis, DNA molecules moves towards positively charged anode because DNA is negatively charged molecules.
• The molecules separate out due to difference in molecular weight.

Tapetum secretes Ubisch bodies which get covered with sporopollenin and so increase thickness of exine of pollen grain wall. Tapetum provides nourishment to developing microspores. It also secretes callase enzyme which dissolves callose substances by which four pollens of a pollen tetrad are united, hence separating microspores or pollens of a tetrad.

Genetic engineering involves:
(i) Identifying DNA with desirable genes.
(ii) Introduction of identified DNA into the host.
(iii) Maintenance of introduced DNA in the host.
(iv) Transfer of DNA in its progeny.

Hence, option C is correct.

• The polymerase chain reaction is a technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA.
• Calcium ions is not required in PCR technology.

The female gametophyte in angiosperms is called Embryo sac. It contains egg apparatus, antipodal cells and polar nuclei. After fertilisation embryo sac changes into seed.

The development of the male gametophyte in angiosperms is called as microgametogenesis. Pollen grain is the first cell of a male gametophyte. This cell undergoes only two divisions, with the result of first division two cells are formed - a large vegetative cell and a small generative cell. The second division is concerned with generative cell only. This division may take place either in pollen grain or in the pollen tube and gives rise to two male gametes.

Bacillus thuringiensis is not used as a bio-fertitiser but it is used to create transgenic plants.

DNA is coated with tungsten before used in biolistic gun for inserting the DNA directly into target cells for obtaining particular protein.

Xenogamy is the cross-pollination between the flowers of different plants. Cross pollination is the transfer of pollen grains from the anther of one flower to the stigma of a genetically different flower. Cross pollination is performed with the help of an external agency.