Question

Given below are two statements
Statement I: Repetitive DNA can be of two types, e.g., Interspersed Repeat DNA and Tandemly Repeated DNA.
Statement II: Tandemly repeated DNA is also called as satellite DNA.
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Tandem = Like a "Tandem Bicycle" (one behind the other).
Satellite = Named after the Centrifugation Density profile, not space!
Tandem repeats are the basis for DNA Fingerprinting.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests the classification of the non-coding, repeated sequences that make up a large portion of eukaryotic genomes.

Step 2: Detailed Explanation:

• Classification of Repetitive DNA (I): Repetitive DNA is broadly divided into two structural categories based on their arrangement.
- Interspersed Repeats: These are sequences (like SINEs and LINEs) that are scattered throughout the genome. They are often mobile elements.
- Tandem Repeats: These are sequences that occur one after another in a head-to-tail fashion in a localized region. Statement I is correct.

• Satellite DNA (II): Tandemly repeated sequences are often referred to as Satellite DNA. This name comes from the fact that during density-gradient centrifugation, these highly repetitive regions form "satellite bands" distinct from the bulk genomic DNA because of their different base composition (GC content).

• Subcategories: Satellite DNA is further classified based on the length of the repeat unit into:
- Satellites: Large blocks at centromeres.
- Minisatellites: (VNTRs) units of 10-60 bp.
- Microsatellites: (SSRs) units of 1-6 bp.
Therefore, Statement II is also correct.

Step 3: Final Answer:
Both statements accurately describe the standard nomenclature and classification of repetitive DNA elements in genomics.