Biology

DNA and Genetics

1,095 Questions

DNA and genetics questions explore molecular biology, DNA replication, and genetic engineering techniques. These topics are essential for various competitive exams requiring a strong foundation in life sciences. Practice these questions to understand complex biological processes thoroughly.

DNA replication mechanismsGenetic engineering techniquesGene editing toolsPolymerase chain reactionDNA sequencing methods

DNA and Genetics Questions

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Choose the correct answer from the alternatives given :
The enzyme DNA dependent RNA polymerase catalyses the polymerisation reaction in ________ direction.

  1. Only 5 $\rightarrow$ 3
  2. Only 3 $\rightarrow$ 5

  3. Both (a) and (b)

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The two strands have opposite polarity and the DNA-dependent RNA polymerase also catalyze the polymerization in only one direction, that is, 5 →→ 3, the strand that has the polarity 3 →→ 5 acts as a template, and is also referred to as template strand. The other strand which has the polarity 5 →→ 3 and the sequence same as RNA (except thymine at the place of uracil) is displaced during transcription. This strand (which does not code for anything) is referred to as coding strand.

So, the correct answer is 'Only 5 → 3'.

Multiple choice dna replication replication and protein synthesis nucleic acids and protein synthesis heredity biology

Choose the correct answer from the alternatives given :
Other than DNA polymerase, which are the enzymes involved in DNA synthesis?

  1. Topoisomerase

  2. Helicase

  3. RNA primase

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Process of DNA synthesis whereby a parent DNA molecule is faithfully copied, giving rise to two identical daughter molecules is called DNA replication. In DNA synthesis, DNA polymerase plays an important role having the capability to elongate an existing DNA strand but cannot initiate the synthesis. So, the synthesis is initiated with the help of RNA primer formed by RNA primase RNA primase synthesises the short RNA primer of about 10 nucleotides that is elongated by DNA polymerase to form an Okazaki fragment of DNA during DNA replication. Helicase unzips the two strands of DNA and topoisomerase reduces the coiling tension developed due to the unwinding of the two strands.

So the correct answer is 'All of these'.

Multiple choice zoology biotechnology and its applications transgenic animals transgenic organisms applications of biotechnology

Read the following four statements (A-D).

A. The first transgenic buffalo, Rosie produced milk which was human alpha-lactalbumin enriched.
B. Restriction enzymes are used in isolation of DNA from other macromolecules.
C. Downstream processing is one of the steps of rDNA technology.
D. Disarmed pathogen vectors are also used in transfer of rDNA into the host.

Which of the two statements have mistakes?

  1. B and C

  2. C and D

  3. A and C

  4. A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement A is incorrect because Rosie was a transgenic cow, not a buffalo. Statement B is incorrect because restriction enzymes are used to cut DNA at specific sites, not for the isolation of DNA from other macromolecules (which is done via chemical extraction).

Multiple choice zoology biotechnology and its applications transgenic animals transgenic organisms applications of biotechnology

In which of the following method, foreign DNA is coated on the tungsten particle?

  1. Microprojectile gun method

  2. Microinjection method

  3. Liposome-mediated gene transfer

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Microprojectile gun method is a device for delivering exogenous DNA to cells. Here, the impregnation of the cells with nucleic acid or with other biological molecules is achieved by coating the molecules that are intended to be introduced in to the cells on to micro carriers which generally is high density tungsten micro particles.
Microinjection is a technique of delivering foreign DNA into a living cell through a glass micropipette.
Liposome-mediated gene transfer is cell-type-specific gene transfer vehicles in vitro and in vivo using liposome.
so, the correct answer is option A.
Multiple choice zoology biotechnology and its applications transgenic animals transgenic organisms applications of biotechnology

Reporter genes which are used in transformation are of types

  1. Selectable marker gene

  2. Scoreable marker gene

  3. Antibiotic resistant gene

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Reporter genes are classified into selectable markers (which allow survival under selective pressure) and scoreable markers (which allow visual identification of transformed cells).

Multiple choice zoology biotechnology and its applications transgenic animals transgenic organisms applications of biotechnology

Which of the following is a function of a selectable marker?

  1. Provides resistance against a substrate

  2. Inhibits the growth of normal cell in a culture

  3. Help to create a chromosome map

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Selectable markers provide a survival advantage (like antibiotic resistance) to transformed cells while inhibiting the growth of non-transformed cells in a selective medium.

Multiple choice zoology aids to health immunity and the lines of immunity immune system of the body immunity and blood groups
Read the passage and answer the following question.
Many mammalian cell membrane receptors associated with the immune system contain repetitive structures known as the immunoglobulin fold. Receptors containing even one of these folds are considered members of the immunoglobulin superfamily. 
Which of the following explains this common feature in different molecules?

  1. All of the genes that produce these proteins used to be part of a much larger gene that fragmented in the past

  2. All of the genes in question are retrotransposons

  3. Most of the genes in question are introns that experienced mutations that removed the splice sequence

  4. The fold was so successful as a signaling molecule that it encouraged its propagation

  5. The fold is repetitive because of gene duplication
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Repetitive gene products are produced by gene duplication. A duplicated gene produces the same protein in multiple repeats. Retrotransposons can amplify themselves but are not necessarily present in multiple copies at the same chromosomal location. Introns are noncoding sequences. Proteins are encoded by genes only; they are not a product of encouraged propagation caused by relative success in the functioning. So, the correct answer is option E.

Multiple choice expression of gene inherited changes biology

In E.coli _________________________ genes are grouped in  _______________ operon.

  1. $64,20$
  2. $3,100$
  3. $34,10$
  4. $260,75$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In E.coli, a single circular, nacked dsDNA molecule act as a genetic material. It contains 64 genes and are grouped into 20 operons.

So, the correct option is ’64, 20’.

Multiple choice expression of gene inherited changes biology

Functioning of structural genes is controlled by

  1. Operator

  2. Ligase

  3. Regulator gene

  4. Polymerase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Operon can be defined as DNA segment having a cluster of genes which are controlled by single promoter. It consists of operator gene and structural genes. The operator gene regulates the expression of structural genes by providing a binding site to transcription factor which in turn regulate the gene expression by altering the binding of RNA polymerase to the promoter region. A promoter is a DNA segment where transcription of a particular gene starts. The regulator genes code for transcription factor/repressor proteins that binds to operators or promoters and prevent RNA polymerase from transcribing RNA. The alteration in repressor proteins by inducers make them unable to bind DNA and allow RNA polymerase to carry out transcription. Thus regulator gene control the functioning of structural genes via operator gene. Option C is correct answer.

Multiple choice expression of gene inherited changes biology

Functioning of structural genes is controlled by

  1. Operator

  2. Promoter

  3. Ligase

  4. Regulator gene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Operon can be defined as DNA segment having a cluster of genes which are controlled by single promoter. It consists of operator gene and structural genes. The operator gene regulates the expression of structural genes by providing a binding site to transcription factor which in turn regulate the gene expression by altering the binding of RNA polymerase to the promoter region. A promoter is a DNA segment where transcription of a particular gene starts. Ligase enzymes facilitate the joining of two DNA strand together by phosphodiester bonds. The regulator genes code for transcription factor/repressor proteins that binds to operators or promoters and prevent RNA polymerase from transcribing RNA. The alteration in repressor proteins by inducers make them unable to bind DNA and allow RNA polymerase to carry out transcription. Thus regulator gene control the functioning of structural genes via operator gene. Option D is correct answer.

Multiple choice expression of gene inherited changes biology

A co-ordinated unit which controls the genetic expression is called as a/an

  1. Cistron

  2. Recon

  3. Operon

  4. Muton
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Cistron: Is a section of a DNA or RNA molecule that codes for a specific polypeptide in a protein synthesis.
Recon: In a cistron, the recombinational units may be more than one. Thus, the smallest unit capable of undergoing recombination is called as a recon.
Muton: It may be defined as, "the smallest unit of DNA which may be changed is the nucleotide''. Therefore, cistron is the largest unit in size followed by recon and muton. This can be explained that a gene consists of several cistron, a cistron contains many recons and a recon contains a number of mutons. 
Operon: It is a unit of genetic material that functions in a co-ordinated manner by means of an operator, a promoter and one or more structural genes that are transcribed together.
Thus, the correct answer is option C.
Multiple choice expression of gene inherited changes biology

Operon contains

  1. Operator and regulator genes

  2. Operator and structural genes

  3. Operator, regulator genes and repressor

  4. Operator gene, regulator gene, repressor gene, structural genes and promoter gene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Operator gene is a segment of DNA present between the promoter and the genes of the operon. It helps in transcribing the genes of the operon.
  • Regulator gene often codes for repressor proteins which bind with the operator and checks the operon.
  • Repressor gene physically obstructs the RNA polymerase from transcribing the genes by binding with the operator gene.
  • Structural genes are the genes that undergo translation to produce enzymes and are co-regulated by the operon.
  • Promoter gene is a nucleotide sequence that enables a gene to be transcribed. It is recognized by RNA polymerase, which then initiates transcription.
So, the correct option is 'Operator gene, regulator gene, repressor gene, structural genes and promoter gene'.

Multiple choice expression of gene inherited changes biology

Which of the following is an example of positive gene regulation?

  1. The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.

  2. The lac gene, in which the repressor preventing the synthesis of the enzymes that degrade lactose is deactivated by the presence of lactose.

  3. CAP, which acts as a required transcription factor for the enzymes that degrade lactose.

  4. All of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Regulation of functioning of the expression of genes is known as the regulation of gene expression. It is basically of three types- inducible, constitutive and repressible.

The repressible kind of control is when the product of regulatory gene initiates the expression of the gene under its control.
The tryptophan consists of repressible Operon model in which when the end product tryptophan is present in sufficient amount it's molecules act as corepressor and the structural genes become switched this is also known as feedback repression or positive regulation.

So, the correct option is 'The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.'