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Q8(a):
Differentiate between the followings:
Repetitive DNA and Satellite DNA
Solution :
1. Definitions and Fundamental Nature
The distinction between Repetitive DNA and Satellite DNA is rooted in the architecture of the eukaryotic genome and the density-gradient centrifugation profiles of nuclear DNA.
- Repetitive DNA: These are sequences of DNA that are repeated many times throughout the genome, ranging from a few times to millions of copies. They can be categorized into tandem repeats (clustered together) or interspersed repeats (transposable elements distributed throughout). [Per the Human Genome Project findings on non-coding regulatory sequences].
- Satellite DNA: This is a specific subset of repetitive DNA consisting of short, highly repetitive sequences (often 2–100 base pairs) arranged in tandem arrays. These sequences have a different base composition (GC/AT ratio) than the bulk genomic DNA, allowing them to form distinct "satellite" bands when subjected to density-gradient centrifugation.
2. Comparative Analytical Table
| Feature | Repetitive DNA | Satellite DNA |
|---|---|---|
| Scope | Broad category encompassing all repeated sequences. | Specific sub-category of tandemly repetitive DNA. |
| Physical Distribution | Can be tandemly arranged or interspersed (e.g., SINEs, LINEs). | Always arranged in tandem arrays (head-to-tail). |
| Centrifugation Profile | Does not necessarily form distinct bands separate from bulk DNA. | Forms distinct 'satellite' bands due to significant differences in buoyant density. |
| Functional Context | Often involved in structural maintenance, regulation, and transposition. | Highly concentrated in heterochromatic regions (centromeres, telomeres). |
3. Structural Visualization
4. Theoretical Justification
The distinction is fundamentally based on Buoyant Density. Satellite DNA is characterized by high rates of polymorphism. Because these sequences do not code for proteins [Per the Central Dogma constraints], high mutation rates are tolerated, leading to a high degree of variation in the number of copies between individuals. This variation is the basis for DNA Fingerprinting (VNTRs—Variable Number Tandem Repeats). In contrast, "Repetitive DNA" is an umbrella term; if a repetitive element is transcribed (like some mobile genetic elements), its structural constraints are much stricter.
Final Solution: Repetitive DNA represents a broad classification of all repeated sequences in the genome, which may be scattered or clustered. Satellite DNA is a specific, restricted subset of repetitive DNA that is arranged in tandem arrays, possesses a distinct buoyant density from bulk genomic DNA, and is concentrated in highly condensed heterochromatic regions.
More Questions from Class 12 Biology Molecular Basis of Inheritance EXERCISES
- Q1: Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
- Q1: Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
- Q2: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
- Q2: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
- Q3: If the sequence of one strand of DNA is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of complementary strand in 5'\(\rightarrow\)3' direction.
- Q3: If the sequence of one strand of DNA is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of complementary strand in 5'→3' direction.
- Q4: If the sequence of the coding strand in a transcription unit is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of mRNA.
- Q4: If the sequence of the coding strand in a transcription unit is written as follows: 5' -ATGCATGCATGCATGCATGCATGCATGC-3' Write down the sequence of mRNA.
- Q5: Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q5: Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q6: Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
- Q6: Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
- Q7: How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
- Q7: How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
- Q8(a): Differentiate between the followings: (a) Repetitive DNA and Satellite DNA
- Q8(b): Differentiate between the followings: mRNA and tRNA
- Q8(b): Differentiate between the followings: (b) mRNA and tRNA
- Q8(c): Differentiate between the followings: Template strand and Coding strand
- Q8(c): Differentiate between the followings: (c) Template strand and Coding strand
- Q9: List two essential roles of ribosome during translation.
- Q9: List two essential roles of ribosome during translation.
- Q10: In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
- Q10: In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
- Q11(a): Explain (in one or two lines) the function of the followings: (a) Promoter
- Q11(a): Explain (in one or two lines) the function of the followings: Promoter
- Q11(b): Explain (in one or two lines) the function of the followings: (b) tRNA
- Q11(b): Explain (in one or two lines) the function of the followings: tRNA
- Q11(c): Explain (in one or two lines) the function of the followings: (c) Exons
- Q11(c): Explain (in one or two lines) the function of the followings: Exons
- Q12: Why is the Human Genome project called a mega project?
- Q12: Why is the Human Genome project called a mega project?
- Q13: What is DNA fingerprinting? Mention its application.
- Q13: What is DNA fingerprinting? Mention its application.
- Q14(a): Briefly describe the following: (a) Transcription
- Q14(a): Briefly describe the following: Transcription
- Q14(b): Briefly describe the following: (b) Polymorphism
- Q14(b): Briefly describe the following: Polymorphism
- Q14(c): Briefly describe the following: (c) Translation
- Q14(c): Briefly describe the following: Translation
- Q14(d): Briefly describe the following: (d) Bioinformatics
- Q14(d): Briefly describe the following: Bioinformatics
CBSE Solutions for Class 12 Biology Molecular Basis of Inheritance
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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