Find the best tutors and institutes for Class 12 Tuition
Q5:
Do eukaryotic cells have restriction endonucleases? Justify your answer.
Solution :
Theoretical Foundation: Defining Restriction Endonucleases
Restriction endonucleases are a class of enzymes categorized under nucleases that possess the specific ability to cleave phosphodiester bonds within a DNA molecule at highly specific recognition sequences, known as palindromic sites [Per the Restriction-Modification System theory]. These enzymes act as a critical component of the prokaryotic immune mechanism, specifically designed to degrade foreign genetic material, such as bacteriophage DNA, thereby preventing viral replication within the host cell.
Step 1: Analyzing the Presence in Eukaryotes
Eukaryotic cells, by definition, possess complex compartmentalization, including a nucleus surrounded by a nuclear membrane. Their genomic defense mechanisms are evolutionary distinct from the prokaryotic Restriction-Modification (R-M) systems. Based on current genomic sequencing and biochemical assays, eukaryotic cells do not possess restriction endonucleases.
Step 2: Justification through Evolutionary Strategy
The absence of restriction endonucleases in eukaryotes is supported by the following biological rationales:
- Defense Mechanism Divergence: Eukaryotes utilize alternative, more sophisticated mechanisms for defense against invasive nucleic acids, primarily RNA interference (RNAi), CRISPR-Cas systems (in specialized prokaryotes/archaea, which are distinct from the eukaryotic genome), and the interferon response in vertebrates.
- Genomic Integrity: Restriction endonucleases function by recognizing short, specific palindromic sequences (typically 4–8 base pairs). The eukaryotic genome is vast and rich in repetitive sequences; the presence of such enzymes would pose a lethal threat of self-cleavage (autodigestion) to the organism's own DNA.
- Methylation Constraints: In prokaryotes, restriction endonucleases are paired with methyltransferases that modify the host DNA to prevent self-cleavage. While eukaryotes utilize methylation (e.g., DNA methyltransferase activity), it is used for gene regulation and epigenetic silencing rather than shielding against restriction endonucleases.
Visual Representation of Restriction Logic
Step 3: Comparative Analysis
| Feature | Prokaryotic Cells | Eukaryotic Cells |
|---|---|---|
| Presence of Restriction Enzymes | Present (Defense mechanism) | Absent |
| Primary Defense | Restriction-Modification System | RNAi, Interferons, Innate Immune Response |
| Genome Complexity | Low (Usually circular) | High (Linear, complex chromatin) |
Final Solution: Eukaryotic cells do not have restriction endonucleases. Their absence is essential because eukaryotic genomes contain numerous potential recognition sites; the presence of such enzymes would lead to spontaneous fragmentation of the host's own DNA, proving fatal. Eukaryotes have evolved more complex immune mechanisms, such as RNA interference, which do not rely on the cleavage of specific palindromic DNA sequences.
More Questions from Class 12 Biology Biotechnology: Principles and Processes EXERCISES
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q11(a): Explain briefly (a) PCR
- Q11(a): Explain briefly (a) PCR
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(c): Explain briefly (c) Chitinase
- Q11(c): Explain briefly (c) Chitinase
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
CBSE Solutions for Class 12 Biology Biotechnology: Principles and Processes
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
Top Tutors who teach Biotechnology: Principles and Processes
Top Tutor
R - Block, Kovaipudur
20 yrs of
Exp
16 students
296 hrs of classes completed
500
per hour
Online Classes
I have 21 years of experience in teaching chemistry and training the students for both board and competitive exams.
Top Tutor
Ma Periyar Bus Stand, Madurai
20 yrs of
Exp
250
per hour
Online Classes
My Qualification : M.com., M.A., M.Phil., M.Ed I have total 30+ years of experience handling following subjects : 1] Accountancy 2] Cost Accountancy 3] Management Accountancy 4] Business Management 5] English for B.Ed only For the following Degrees : B.Com, B.B.A., M.B.A., +1 & +2 [Commerce and Accountancy] Rich Teaching Experoences i various colleges.
Top Tutor
Hiran Magri Sector 14, Udaipur
6 yrs of
Exp
20 students
3758 hrs of classes completed
400
per hour
Online Classes
I am doing work as a home tutor for the last 6 years. currently, I am pursuing a Ph.D. in Economics. I am confident about my skills, and if you will show confidence in me I am sure I leave up to your expectations. if you looking for a good mentor then go and check my profile and book the demo session now. Thank you so much.
She is very dedicated educator. Always understand child needs and preferences. My child is satisfied. She is available for anytime help.
Top Tutor
Malkajgiri D.D.Colony, Hyderabad
20 yrs of
Exp
21 students
1580 hrs of classes completed
500
per hour
Online Classes
32+ years of teaching. Conducted online classes for more than 10 years. Prepared question papers and materials. Teaching students preparing for IIT, VITEE, COMEDK and other entrance examinations. Teach problems from various other authors, other state books and train students for their examinations. Conducted weekly quizzes and unit wise tests. Also conducted mock examinations before the board exam
Top Tutor
Sector 54, Chandigarh
15 yrs of
Exp
10 students
259 hrs of classes completed
750
per hour
Online Classes
i am physics teacher with 15 years of experience in teaching 11,12, competitive exams. i always try to explain topics more in practical form rather than theortical by giving examples from day to day life . topics like electrostatics , alternating current ,optics , semiconductors and logic gates are most imp and students usually got troubled there but with practical apporoach i make them go with happy and easy learning .
Puts in genuine effort Clear concepts Offer flexible timings Cover all types of questions in class Excellent teacher
Other Subjects in CBSE - Class 12
Download free CBSE - Class 12 Biology Biotechnology: Principles and Processes EXERCISES worksheets
Download Now
