Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

51.

Assertion : Endothecium layer of anther wall plays an important role in dehiscence of anther.

Reason : The presence of fibrous bands and differential expansion of inner and outer tangential walls of endothecial cells cause dehiscence of anther.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


A.

If both assertion and reason are true and reason is the correct explanation of assertion

Dehiscence is the splitting along a built- in line of weakness in a plant structure in order to release its contents and is among fruits, anthers and sporangia.


52.

Assertion : The technique of micropropogation has been used to introduce variations in the offspring.

Reason : It is not possible to generate virus free plants by micropropogation.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false

  • If both assertion and reason are false


D.

If both assertion and reason are false

Micropropagation is used for rapid vegetative multiplication of plants. As the size of the propagule is minute, thus the technique is named micropropagation. Each, such plant, will be genetically identical to the parent plant. Generally, apical or axillary meristems are free from viruses. Hence, can be used as explants in tissue culture to produce virus free plants.


53.

The number of chromosomes present in the cells of the bread wheat, Triticum aestivum suggests that it is

  • hexaploid

  • diploid

  • tetraploid

  • pentaploid


A.

hexaploid

Bread wheat is an allohexaploid, an allopolyploid, with six sets of chromosomes.


54.

Assertion : Hardy-Weinberg principle states that in the absence of disturbing influences, gene frequencies of large populations of sexually reproducing organisms do not change, provided that matings, occur at random.

Reason : The disturbing influences include mutation, gene flow, genetic drift, genetic recombination and natural selection.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


B.

If both assertion and reason are true but reason is not the correct explanation of assertion

According to Hardy-Weinberg principle gene frequencies will remain constant if there is no mutation, no gene flow, no genetic drift, no genetic recombination, no natural selection pressure and mating occurs at random.


55.

Assertion : Curdling is required in the manufacture of cheese.

Reason : Lactic acid bacteria are used for the purpose.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false

  • If both assertion and reason are false


B.

If both assertion and reason are true but reason is not the correct explanation of assertion.

Some cheeses are curdled only by acidity. For example, paneer cheese is made using lemon juice to curdle the milk and cottage is made using mesophilic bacteria. For most cheeses, rennet is also added to the milk after a starter bacteria.


56.

Assertion : Curdling is required in the manufacture of cheese.

Reason : Lactic acid bacteria are used for the purpose.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


C.

If assertion is true but reason is false

Chromosomal or allosomic determination of sex is based on heterogamety or occurence of two types of gametes in one of the two sexes. Male heterogamety is found in allosome complements XX-XY and XX-XO. In birds and some reptiles both the sexes possess two sex chromosomes but unlike human beings the females contain heteromorphic sex chromosomes (AA + ZW) while the males have homomorphic sex chromosomes (AA + ZZ).


57.

Assertion : Foetal disorders can be diagnosed by chorionic villi sampling.

Reason : Karyotyping can be done for mitotically dividing cells of chorionic villi.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


A.

If both assertion and reason are true and reason is the correct explanation of assertion.

During early pregnancy, foetal disorders can be diagnosed using chorionic villi sampling. In this technique the physician inserts a narrow, flexible tube through the mother's vagina and cervix into the uterus (guided by ultrasound) and withdraws a small amount of foetal tissue (chorionic villi) from the placenta. Because the cells ofthe chorionic villi are undergoing rapid mitosis, these cells can be used for karyotyping.


58.

Assertion : IgM is a type of immunoglobulin which cannot cross the placenta.

Reason : IgM is pentamer immunoglobulin, joined by J-chain

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false.

  • If both assertion and reason are false


A.

If both assertion and reason are true and reason is the correct explanation of assertion

IgM cannot cross the placenta because the body tends to make IgG antibodies against the Rh antigen. IgM antibodies are made against the A and B antigens.


59.

If 'A' represents the dominant gene and 'a' represents its recessive allele, which of the following would be the most likely result in the first generation offspring when Aa is crossed with aa ?

  • All will exhibit dominant phenotype

  • All will exhibit recessive phenotype

  • Dominant and recessive phenotypes will be 50% each

  • Dominant phenotype will be 75%


C.

Dominant and recessive phenotypes will be 50% each

'A' represents the dominant gene and 'a' represents its recessive allele. The most likely result in the first generation offspring when Aa is crossed with aa is :

Parents          :  Aa × aa

Gametes        : A, a, a, a

F1 generation : Aa Aa aa aa

Hence, Aa : aa = 1 : 1


60.

Assertion :  Number of chromosomes in one genome is equal to number of linkage groups.

Reason : Linkage groups give important information about the location of genes in the chromosomes.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false

  • If both assertion and reason are false


B.

If both assertion and reason are true but reason is not the correct explanation of assertion.

Linkage group, in genetics, all of the genes on a single chromosome. They are inherited as a group; that is, during cell division they act and move as a unit rather independently. The existance of linkage groups is the reason some traits do not comply with Mendel's law of independent assortment; ie, the principle applies only if genes are located on different chromosomes.