Sample Test: Biology - NEET MCQ

• Classes comprising animals like fishes, amphibians, reptiles, birds along mammals constitute the next higher category called Phylum.
  All these classes are included in the phylum Chordata.
• In the case of plants, classes with a few similar characters are assigned to a higher category called Division.

Classification of taxonomical unit:
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All living organisms share common genetic material, i.e., DNA but with variations.
Example: Bacteria have single-stranded circular DNA while in highly evolved eukaryotic cells of plants and animals, DNA is a long double-stranded helix.

• Viruses did not find a place in classification since they are not truly ‘living’ if we understand living as those organisms that have a cell structure.
• Viruses are neither prokaryotes nor eukaryotes.
• They are inert outside their specific host cell and cannot multiply of their own because they lack cellular machinery to use its genetic material.
• Viruses can only multiply in host or living cell.

• Phycomycetes are the members of fungi that can thrive well on dead and decaying wood as saprophytes.
• These prefer to live in moist and damp places and need water for the movement of zoospore and sexual gametes and few members of Phycomycetes are obligate parasites like Phytophthora.

• Fruits can develop from a single ovary of a single flower (simple fruit) or from several free carpels of a single flower (aggregate) or from whole inflorescence (multiple). In total, fruits develop from ovaries.
• This is why a dioecious plant (unisexual) bearing only staminate(male) flowers will not produce fruits, whereas monoecious plants (bisexual) or dioecious plant bearing only pistillate (female) flowers or pistillate and staminate both can bear fruits.

Types of flower:​

A typical microsporangium is generally surrounded by four-wall layers, i.e., the epidermis, (outermost protective layer), endothecia, (middle fibrous layers), and the tapetum (innermost nutritive layer).

Microsporangium of Anther:

The correct sequence of parts in an ovule is (innermost to outermost):

Egg - Embryo sac - Nucellus - Integument

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• Autogamy is pollination within a flower. Chasmogamous flowers are those in which anthers and stigma are exposed.
• For autogamy, in such a flower to take place, pollen and ovule should mature simultaneously and anther and stigma should lie close to each other.

• Pollination by wind is called anemophily.
• Anemophilous flowers are small, inconspicuous non-scented without bright colours, nectar and fragrance.
• Wind pollination also requires that the pollen grains are light and non-sticky which is in large numbers and its stigmas are long and feathery.

• Autogamy (same flower)
• Geitonogamy (different flowers of same plants)
• Xenogamy (different plant’s flower)

Dioecious plant bearing only male or female flowers prevents both autogamy and geitonogamy.

• All the genes located on the same chromosome form one linkage group.
• A linkage group can be defined as all the genes on a single chromosome that move as a unit during the cell division.
• These genes do not tend to separate, until the crossing-over and if the distance between them is very less, they will not undergo the crossing-over.
• Examples: Human beings have 23 linkage groups due to 23 pairs of chromosomes.

The Formation of Recombinant Chromosomes via Crossing Over:

Mycorrhiza helps the host plant in:

• Enhancing its phosphorus uptake capacity,
• In increasing its tolerance to drought.
• Some chemicals which resist the pathogen like Fusarium.

So, the correct option is 'increasing its resistance to insects'

Both genes are equally expressed hence its co-dominance.

Tt and Tt let's use Mendel's cross of tall and dwarf pea plants as an example. The F₁ plants of genotype Tt are self-pollinated. (both tall (T) but with dwarf (t) alleles).

• The letters T and t are used to represent the alleles of the gene that determine plant height by conventions.
• The upper case letter (T) represents the dominant allele and the recessive allele (t) is represented by the same letter in lower case. Thus, the tall parents plants having heterozygous alleles, results in off springs which comprises of both tall and dwarf plants.
• For the parental cross, both the parents are true breeding plants, the tall plant is homozygous for the tall allele T, while the dwarf plant is homozygous for the dwarf allele 't'.
• Mendel tracked each trait through two generations. When true breeding plants were crossed to each other, this is called a parental cross and offspring comprise the first filial or F1 -generation.
• When the members of the F1 - generation were crossed, this produced the F2 - generation or second filial generation.
• A cross between true breeding tall and dwarf plants of the parent generation yield phenotypically tall plants.
• The cross between TT and Tt is called back cross, which results into two homozygous and two heterozygous dominant gametes.
• The cross between Tt and tt is called testcross which results into 1:1 ratio of gametes.

• Cross involving two contrasting characters is called dihybrid cross.
• The two flowers of each trait assort at random and independent of their traits at the time of meiosis (gametogenesis) and get randomly as well as independently rearranged in the offspring producing both parental and new combinations of traits.
• This explained the law of independent assortment given by Mendel.

• Mendal's Law of independent assortment tells us that the pairs of the alleles get separated when the gametes are being formed which means the traits or characters that are being transferred to the offspring are independent.
• Now the non-homologous chromosomes are different from each other completely and they do not take part in crossing-over.

Relationship between Chromosomes and chromatids:

• Occasionally, a single gene may express more than one trait. This phenomenon is called pleiotropy.
• Sometimes, one trait will be very evident and others will be less evident,
  Example: A gene for white eye in Drosophila also affect the shape of organs in male responsible for sperm storage as well as other structures.
• Similarly, sickle-cell anemic individuals suffer from a number of problems, all of which are pleiotropic effects of the sickle-cell alleles.
• Multiple allelism is a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal diploid individual,
  Example: Genes of blood groups in humans. Mosaicism describes the occurrence of cells that differ in their genetic component from other cells of the body.
• Polygeny refers to a single characteristic that is controlled by more than two genes. (it is also known as multifactorial inheritance).

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In the F₂ generation of a Mendelian dihybrid cross, the number of phenotypes and genotypes are 4, 9 respectively.

Two nucleotides are linked through 3 → 5 phosphodiester linkage to form a dinucleotide. More nucleotides are joined in a similar manner to form a polynucleotide chain.

Heterozygous for A and B ;Hemizygous for h.
Therefore the genotype would be:
AaBbXh Y
(hemizygous for h as in for human males can only fall on X)
(hemizygous for female would be Xh X)
All the kinds of gametes you can get with this,,,
abXh
ABXh
abY
AbY
aBX
aBY
ABY
AbXh
but they are asking for portion of abXh..
Therefore its 1 / 8
So, the correct answer is '1 / 8'. 

• During oogenesis, each primary oocyte gets surrounded by a layer of granulosa cells and then called the primary follicle.
• The primary follicles get surrounded by more layers of granulosa cells and a new theca and called secondary follicles.
• The secondary follicle soon transforms into a mature tertiary follicle or Graafian follicle, which is characterized by a fluid-filled cavity, called an antrum. 

So, the correct answer is 'Graafian follicle of ovary'

Lipids are actually triglycerides .a triglyceride consist of glycerol and fatty acids which are held together by Ester linkages in condensation reaction releasing three water molecules.

• Carolus Linnaeus was a Swedish botanist, physician, and zoologist who created the binomial nomenclature.
• In this system, every kind of animal and plant is given a name consisting of two Latin words, for its genus and species.

Earthworms use the prostomium to see their environment, as earthworms have no eyes, ears, nose or hands. They depend on the prostomium and skin to help it feel their way through the soil.

• WBC helps in immunity.
• The main job of white blood cells, or leukocytes, is to fight infection.
• There are several types of white blood cells and each has its own role in fighting bacterial, viral, fungal, and parasitic infections.

The nucleus is responsible for the synthesis of three types of RNA molecules: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). The synthesis of mRNA, tRNA, and rRNA takes place in the nucleus through the process of transcription.

However, the synthesis of g-RNA (guide RNA) takes place in the mitochondria of the cell. g-RNAs are involved in the process of RNA editing, which occurs in the mitochondria of eukaryotic cells. RNA editing involves the insertion, deletion, or modification of nucleotides in the RNA molecule, which can change the amino acid sequence of the protein that is ultimately produced.

Classification of chromosomes is based on position of middle part of centre of chromosome which is known as centromere.

Sub-metacentric chromosome or submedian centromere: The centromere is present slightly away from the center of a chromosome or nearer to one end of the chromosome. As a result, the chromosome is divided into one shorter and one long arm.

Types of chromosomes:

• Chitin is a long-chain polymer of a N-acetylglucosamine.
• It is a nitrogen containing polysaccharide and a derivative of glucose.
• It is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans and insects, the radulae of molluscs, and the beaks and internal shells of cephalopods, including squid and octopuses.

Essential chemical components of many coenzymes are vitamins,
Example: Coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.