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 Multiple Choice QuestionsMultiple Choice Questions

141.

Beads on string like structures of A are seen in B, which further condense to form chromosomes in C stage of cell division

  •            A              B             C

    Chromonema Chromatin Metaphase

  •         A              B             C

    Chromatin Chromatid Metaphase

  •            A              B             C

    Chromonema Chromosome Anaphase

  •            A              B             C

    Chromonema Chromatid Anaphase.


A.

           A              B             C

Chromonema Chromatin Metaphase

The "beads-on-a-string" structure is seen in electron microscope of isolated metaphase chromosomes. The chromonema form the gene bearing portions of the chromosome. Basically chromonema is made up of nucleosome chains. Nucleosome chain gives a beads on string appearance under electron microscope. Nucleosome is the fundamental packaging unit in eukaryotic chromosomes.


142.

Ribosomal RNA is actively synthesised in 

  • lysosomes

  • nucleolus

  • nucleoplasm

  • nucleoplasm


B.

nucleolus

In eukaryotes, the site of synthesis of most of the ribosomal RNA (rRNA) is nucleolus. The nucleolar organiser contains many copies of ribosomal DNA (repetitive DNA). The RNA cistron of nucleolar DNA forms 45 S precursor with the help of RNA polymerase. This 45 S RNA undergoes to give 18S, 28S and 5.8 S rRNA units. Out of different rRNAs, the 5S rRNA is not synthesized in nucleolus. It is synthesized outside it. 

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143.

Read the following four statement.
1. In transcription, adenosine pairs with uracil
2. Regulation of lac operon by repressor is referred to as positive regulation.
3. The human genome has approximately 50,000 genes.
4. Haemophilia is sex-linked recessive disease.

How many of the above statements are right?

  • Two

  • Three

  • Four

  • Four


A.

Two

Transcription is the process of synthesis of RNA on the DNA template. During transcription adenosine pairs with uracil. 
Repressor gene determines the transcription of structural gene. It codes for repressor protein. After synthesis the repressor molecule is diffused from the ribosome and bind to the operator in absence of inducer.
The human genome has approximately 30000 genes with ~ 3.2 billion base pairs.

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144. Which one is a true statement regarding DNA polymerase used in PCR?
  • It is used to ligate introduced DNA in recipient cells

  • It serves as a selectable marker

  • It is isolated from a virus

  • It is isolated from a virus


D.

It is isolated from a virus

Polymerase Chain Reaction (PCR) is used to amplify a DNA segment or to synthesize in vitro the multiple copies of gene (or DNA) of interest, using two sets of primers and the enzyme DNA polymerase. This enzyme is isolated from a bacterium Thermus aquatics and it remains active during the high temperature but high temperature induced denaturation of double stranded DNA

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145.

What is it that forms the basis of DNA fingerprinting?

  • The relative proportions of purines and pyrimidines in DNA

  • The relative difference in the DNA occurrence in blood, skin and saliva

  • The relative amount of DNA in the ridges and grooves of the fingerprints

  • The relative amount of DNA in the ridges and grooves of the fingerprints


D.

The relative amount of DNA in the ridges and grooves of the fingerprints

DNA fingerprint is individual-specific DNA identification which is made possible by the finding that no two people are likely to have the same of copies of repetitive DNA sequences of regions. The chromosomes of every human cells contains short, highly repeated DNA sequence (15 nucleotide) called minisatelite scattered throughout. 

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146.

Genetic material found in Human Immunodeficiency Virus (HIV) is

  • Double stranded RNA

  • Single stranded RNA

  • Double stranded DNA

  • Single stranded DNA


B.

Single stranded RNA

Human Immunodeficiency Virus (HIV) is thecausal organism of AIDS (Acquired Immuno Deficiency Syndrome). It is a retrovirus belonging to the family-Retroviridae. The core of HIV contains two molecules of single-stranded RNA (as genetic material) and reversetranscriptase.


147.

Removal of introns and joining of exons in a defined order during transcription in called

  • looping

  • inducing

  • slicing

  • slicing


D.

slicing

The primary transcript from a typical eukaryotic gene contains introns as well as exons. During RNA splicing, introns are removed and exons are joined in a defined order, to produce functional RNA.

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148.

The figure below shows three steps (A, B, C) of Polymerase Chain Reaction (PCR). Select the option giving correct identification together with what it represents?

  • B – Denaturation at a temperature of about 98°C separatiing the two DNA strands

  • A – Denaturation at a temperature of about 50°C

  • C – Extension in the presence of heat stable DNA polymerase

  • C – Extension in the presence of heat stable DNA polymerase


C.

C – Extension in the presence of heat stable DNA polymerase

There are three steps in polymerase chain reaction namely.
(i) Denaturation- at 94 degree straight C for DNA strand separation.
(ii) Annealing - binding of primer.
(iii) Extension in presence of DNA polymerase which is heat stable.

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149.

DNA replication occurs in

  • G1-phase

  • S-phase

  • G2-phase

  • M-phase


B.

S-phase

The s-phase of the cell cycle is also called 'synthesis phase, in which the cell synthesizes the replica of its genome, ie, DNA replication occurs during this stage, which ultimately results to the duplication of chromosomal material.


150.

Given below is the diagrammatic representation of one of the categories of small molecular weight organic compounds in the living tissues. Identify the category shown and the one blank component X in it

  • Category                       Component
    Nucleoside                         Uracil

  • Category                       Component
    Cholesterol                       Guanin
  • Category                       Component
    Amino acid                       NH2
  • Category                       Component
    Amino acid                       NH2

A.

Category                       Component
Nucleoside                         Uracil

Nucleoside is made up of ribose sugar and nitrogenous base only. Uracil forms nucleoside with only ribose sugar. So, the option with category nucleoside component uracil is correct.



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