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 zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

The idea that a single gene coded for a polypeptide rather than an enzyme was evident from the

  1. use of X-rays to make nutritional mutants in bread mold

  2. transformation of bacteria from rough and non-virulent to smooth and virulent

  3. presence of a mutation in one chain of hemoglobin but not in the other

  4. discovery that mutated genes changed enzymes in a biochemical pathway
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to one gene-one polypeptide hypothesis, the information enclosed in one gene is sufficient to form one polypeptide only. Genes control the synthesis of all proteins. Some proteins are enzymes and some are hormones. As we know that proteins are made up of polypeptides- long chains of amino acids. Some proteins consist of two or more polypeptides linked and twisted around each other. For eg, hemoglobin.

So, the correct option is presence of a mutation in one chain of hemoglobin but not in other'.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Studies by Beadle and Tatum that produced the one-gene one-enzyme hypothesis were conducted using the:

  1. bread mold Neurospora crassa

  2. bacterium Streptococcus pneumoniae

  3. bacterium Escherichia coli

  4. mushroom Agaricus bisporus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The one gene-one enzyme hypothesis, proposed by George Wells Beadle in the US in 1941, is the theory that each gene directly produces a single enzyme, which consequently affects an individual step in a metabolic pathway. Beadle and Tatum worked with a simple organism: common bread mold, or Neurospora crassa. Using Neurospora, they were able to show a clear connection between genes and metabolic enzymes. With a series of the experiment they first created mutant Neurospora and found which metabolic pathway was broken in mutants by growing them in a variety of nutritional medium. Their work produced a revolution in the study of genetics and showed that individual genes were indeed connected to specific enzymes. 

So, the correct option is 'bread mold Neurospora crassa'.

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

Which of the following is required for microinjection method of gene transfer?

  1. Microparticles

  2. Micropipettes

  3. Divalent cations

  4. UV radiations
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Micro-injection method is the direct or vectorless method of gene transfer, in which foreign DNA is directly injected into the nucleus of animal cell or plant cell by using micro-needles or micro-pipettes. It is used to transfer DNA in oocytes, eggs and embryo.
So, the correct answer is 'Micropipettes'.
Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

The term "competent" refers to

  1. Increasing the competition between cells

  2. Making cells impermeable for DNA

  3. Increasing the efficiency with which DNA enters the bacterium through pores in its cell wall

  4. Making cells permeable for divalent cations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Transformation is a process by which a cell takes up naked DNA fragment from the environment, incorporates it into its own chromosomal DNA and finally expresses the trait controlled by the incoming DNA. Since DNA is a hydrophilic molecule, it can not pass through membranes, so the bacterial cells must be made competent to take up DNA. This is done by treating them with a specific concentration of a divalent cation, such as calcium ($Ca^{2+}) which increases the efficiency with which DNA enters the bacterium through pores in its cell wall.
So, the correct answer is 'Increasing the efficiency with which DNA enters the bacterium through pores in its cell wall'.
Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure biotechnology in agriculture

Micro-injection is a method used to

  1. Produce sticky ends of DNA

  2. Provide protection against pathogen

  3. Purify the DNA

  4. Inject recombinant DNA into the nucleus of an animal cell
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Micro-injection is a method used to Inject a recombinant DNA into the nucleus of an animal cell. This is the only way to introduce alien DNA into host cells. 

So, the correct option is 'Option D' .

Multiple choice botany biotechnology: principles and processes dna transfer rdna technology - dna transfer and transformation gene cloning procedure biotechnology in agriculture

If a person obtains transformants by inserting a recombinant DNA within the coding sequence of enzyme -galactosidase, he will separate out recombinants from non-recombinants by which of the following observations?

  1. Non-recombinant colonies do not produce any colour whereas recombinants give blue coloured colonies

  2. Recombinant colonies do not produce any colour whereas non-recombinants give blue coloured colonies

  3. Recombinants and non-recombinants both produce blue coloured colonies

  4. No colonies are formed due to insertional inactivation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Alternative selectable markers have been developed which differentiate recombinants from the non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, a recombinant DNA is inserted within the coding sequence of an enzyme, ( -galactosidase. This results into inactivation of the enzyme, which is referred i to as insertional inactivation. The presence of a chromogenic j substrate gives blue coloured colonies if the plasmid in the bacteria does not have an insert. Presence of insert results into insertional inactivation of the -galactosidase and the colonies do not produce any colour, these are identified as recombinant colonies.

Multiple choice botany biotechnology: principles and processes dna transfer rdna technology - dna transfer and transformation gene cloning procedure biotechnology in agriculture

In the process of insertional inactivation ________________.

  1. A recombinant DNA is inserted within the coding sequence of enzyme -galactosidase, resulting in inactivation of the enzyme

  2. A recombinant DNA is inserted within the coding sequence of proteins involved in the replication of the plasmid

  3. A recombinant DNA is inserted within the recognition site for EcoRI

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

Alternative selectable markers have been developed which differentiate recombinants from the non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, a recombinant DNA is inserted within the coding sequence of an enzyme, ( -galactosidase. This results into inactivation of the enzyme, which is referred i to as insertional inactivation. The presence of a chromogenic j substrate gives blue coloured colonies if the plasmid in the bacteria does not have an insert. Presence of insert results into insertional inactivation of the -galactosidase and the colonies do not produce any colour, these are identified as recombinant colonies.

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

If a recombinant DNA bearing gene for resistance to antibiotic ampicillin is transferred to E.coli cells, the host cells become transformed into ampicillin-resistant cells. If such bacteria are transferred on agar plates containing ampicillin, only transformants will grow and the untransformed recipient cells will die. The product produced by transformant bacteria that digests the ampicillin antibiotic is called as - 

  1. Selectable marker

  2. Recombinant protein

  3. Cloning site

  4. Chemical scalpels
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The product produced by the bacteria that digests the antibiotic (like ampicillin) is a protein (an enzyme like beta-lactamase). In the context of recombinant DNA technology, this is a recombinant protein product.

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

The correct sequence of making a cell competent is

  1. Treatment with divalent cations incubation of cells with recombinant DNA on ice heat shock ($42^0$C) placing on ice
  2. Heat shock ($42^0$C) incubation of cells with recombinant DNA on ice treatment with divalent cations placing on ice
  3. Treatment with divalent cations placing on ice incubation of cells with recombinant DNA on ice heat shock ($42^0$C)
  4. Incubation of cells with recombinant DNA on ice heat shock ($42^0$C) treatment with divalent cations placing on ice
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In order to force a bacteria to take up the plasmid , the bacterial cells must to be made competent. This is done by treating them with a specific concentration of divalent cations such as calcium which increases the efficiency with which the DNA molecule enters into the bacteria through pores in its cell wall. Recombinant DNA then forced into such cells by incubating the cells with recombinant DNA on ice followed by placing them immediately at heat shock and then again into ice. This enables the bacteria to take up the recombinant DNA. 

So, the correct option is 'Option A' .

Multiple choice botany biotechnology: principles and processes dna transfer rdna technology - dna transfer and transformation gene cloning procedure biotechnology in agriculture

Statement 1 : In insertional inactivation, blue colour produced by bacterial colonies indicates that the plasmid does not have an insert into the bacterial genome. 
Statement 2: Presence of insert results into insertional inactivation of -galactosidase enzyme and the colonies do not produce any colour.

  1. Both statements 1 and 2 are correct

  2. Statement 1 is correct but statement 2 is incorrect

  3. Statement 1 is incorrect but statement 2 is correct

  4. Both statements 1 and 2 are incorrect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Selectable markers have been developed which differentiate recombinants from non- recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, a recombinant DNA is inserted within the coding sequence of an enzyme B-galactosidase. This results into an  insertional inactivation. The presence of chromogenic substrate gives blue coloured colonies if the plasmid in bacteria does not have an insert. Presence of insert results into insertional inactivation of a^-galactosidase enzyme and the colonies do not produce any colour, these are identified as recombinant colonies. 

So, the correct option is 'Option A' .

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

Chimeric DNA is

  1. Gene clone

  2. Recombinant - DNA

  3. Transposon

  4. Vector shuttle
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Recombinant DNA molecules are sometimes called chimeric DNA, because they can be made of material from two different species, like the mythical chimera.
  • A chimera is essentially a single organism that is made up of cells from two or more individuals—that is, it contains two sets of DNA, with the code to make two separate organisms.
  •  R-DNA technology uses palindromic sequences and leads to the production of sticky and blunt ends.
So, the correct answer is 'Recombinant - DNA'.

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

Competent host in recombinant DNA technology is __________________.

  1. Any human cancer cell

  2. The cell ready to update align DNA

  3. A host cell without cell wall

  4. Agrobacterium cell
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option 'D' is correct.


Competent host is recombinant DNA technology is Agrobacterium cell. Competent host cell is required for transformation with recombinant DNA. Different types of available host cells are like E.cola, yeast, animal and plant cells. Eukaryotic cells will be preferred host, yeast-cells are preferred because this are simple eukaryotic organism and like bacteria are single-celles, easy to grow manipulated. Bacteria also acts enabled to pick up the recombinant-DNA.

Multiple choice botany genetic technology dna transfer rdna technology - dna transfer and transformation gene cloning procedure

The colonies of recombinant bacteria appear white in contrast to blue colonies of nonrecombinant bacteria because of

  1. Inactivation of glycosidase enzyme in recombinant bacteria

  2. Nonrecombinant bacteria contain beta galactosidase
  3. Insertional inactivation of $\alpha$-galactosidase in nonrecombinant bacteria
  4. Insertional inactivation of $\alpha$-galactosidase in recombinant bacteria
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In blue-white screening, the insertion of foreign DNA into the lacZ gene (which encodes beta-galactosidase) causes insertional inactivation, preventing the production of the enzyme and resulting in white colonies.