Biology

DNA and Genetics

985 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 expression of gene inherited changes biology

Wild type Escherichia coli growing on medium having glucose is transferred to lactose containing medium. Which change occurs?

  1. Lac operon is induced

  2. Lac operon is suppressed

  3. All operons are induced

  4. The bacterium stops dividing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When E. coli is moved from glucose to a lactose-containing medium, the lac operon is induced to produce enzymes necessary for lactose metabolism.

Multiple choice expression of gene inherited changes biology

In repressible or negative operon

  1. Corepressor binds with inducer

  2. Corepressor binds with aporepressor

  3. Corepressor does not bind with repressor

  4. cAMP has negative effect
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a repressible operon, the corepressor binds to the inactive aporepressor to form an active repressor complex that can bind to the operator.

Multiple choice expression of gene inherited changes biology

In lac-operon, repressor protein binds to

  1. Regulator gene

  2. Operator gene

  3. Promoter gene

  4. Structural gene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the lac operon, the active repressor protein binds to the operator site, physically blocking RNA polymerase from transcribing the structural genes.

Multiple choice expression of gene inherited changes biology

Operon contains

  1. Operator and regulator genes

  2. Operator and structural genes

  3. Operator and regulator genes, and repressor

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

An operon system typically includes the regulator gene, promoter, operator, and the structural genes it controls.

Multiple choice expression of gene inherited changes biology

Lac operon is

  1. Arabinose operon

  2. Repressible operon

  3. Inducible operon

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

The lac operon is a classic example of an inducible operon, meaning it is typically turned off but can be activated (induced) by the presence of lactose. Repressible operons, by contrast, are typically on and turned off by the presence of a product.

Multiple choice expression of gene inherited changes biology

Operon is

  1. Sequence of three nitrogen bases determining a single amino acid

  2. A set of closely placed genes regulating a metabolic pathway in procaryotes

  3. Segment of DNA specifying a polypeptide

  4. Gene responsible for switching on and switching off of other genes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An operon is a functional unit of DNA in prokaryotes consisting of a cluster of genes under the control of a single promoter and operator, allowing for the coordinated regulation of a metabolic pathway.

Multiple choice expression of gene inherited changes biology

In an inducible operon, the genes are

  1. Usually expressed unless a signal turns them "off

  2. Never expressed

  3. Always expressed

  4. Usually not expressed unless a signal turns them on
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Inducible operons are typically in an 'off' state due to the presence of a repressor protein bound to the operator. They are turned 'on' only when an inducer molecule binds to the repressor, preventing it from binding to the DNA.

Multiple choice expression of gene inherited changes biology

In operon model, the function of regulator gene is to produce

  1. Repressor

  2. Inducer

  3. Corepressor

  4. DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The regulator gene in an operon system codes for a repressor protein, which is responsible for binding to the operator site to inhibit transcription of the structural genes.

Multiple choice expression of gene inherited changes biology

Prokaryotic enzyme with 5'--> 3 exonuclease property is

  1. DNA polymerase I

  2. DNA polymerase II

  3. DNA polymerase III

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

DNA polymerase I is unique among the prokaryotic DNA polymerases because it possesses 5' to 3' exonuclease activity, which is essential for removing RNA primers during DNA replication.

Multiple choice expression of gene inherited changes biology

Which of the following DNA polymerase of prokarytoes have both 3' - 5' and 5' - 3' exonuclease activity

  1. DNA Pol-II

  2. DNA Pol-I

  3. DNA Pol-IV

  4. DNA Pol-III
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA polymerase I is the only prokaryotic DNA polymerase that possesses both 3' to 5' exonuclease activity (for proofreading) and 5' to 3' exonuclease activity (for primer removal).

Multiple choice expression of gene inherited changes biology

In Negative operon : -

  1. Inducer binds with repressor

  2. Co-repressor does not binds with repressor

  3. Corepressor binds with inducer

  4. CAMP have negative effect on lac operon
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The inducer is a molecule that regulates gene expression. An inducer can bind to protein repressors or activators. The lac operon is a negatively controlled inducible operon, where the inducer molecule is Lactose. If the inducer molecule is present, it binds to the repressor and changes its conformation so that it is unable to bind to the operator and thus gene expression is controlled.
So, the correct answer is 'Inducer binds with repressor'.
Multiple choice expression of gene inherited changes biology

The function of a repressor protein in an operon system is to prevent protein synthesis by binding to ________________.

  1. The ribosome

  2. The RNA polymerase, thus blocking transcription

  3. A specify region of the mRNA, preventing translation to protein

  4. A specific region of the operon, preventing transcription of structural genes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In an operon system, a repressor protein binds specifically to the operator region of the operon, thereby physically preventing RNA polymerase from transcribing the structural genes.

Multiple choice expression of gene inherited changes biology

How many of the following statements are correct
(A) In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression
(B) Lac operon is under negative regulation of CAP.
(C) Presence of intron is reminiscent of antiquity.
(D) Inheritance of a character is also affected by promoter and regulatory sequence of a structural gene.

  1. $2$
  2. $3$
  3. $4$
  4. $5$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statements A, C, and D are generally considered correct in biological contexts. Statement B is incorrect because the lac operon is under positive regulation by CAP (Catabolite Activator Protein), not negative regulation. Thus, 3 statements are correct.

Multiple choice expression of gene inherited changes biology

Regulator gene controls chemical synthesis(Operon concept) by.

  1. Inhibiting transcription

  2. Inhibiting enzymes

  3. Inhibiting passage of mRNA

  4. Inhibiting substrate enzyme reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The regulator gene produces a repressor protein that binds to the operator, thereby inhibiting the transcription of the structural genes into mRNA.