Question

Given below are two statements:
Statement (I): STRs are polymorphic tandem repeats of sequences of only two to four nucleotide pairs.
Statement (II): STRs are called microsatellites.
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:

Microsatellites (STRs) have short repeat units (2-6 bp).
Minisatellites (VNTRs) have longer repeat units (10-100 bp).
Both are highly polymorphic and useful as molecular markers.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Repetitive DNA sequences are abundant in eukaryotic genomes.
These sequences are classified based on the length of the repeating unit and are widely used as molecular markers for genetic mapping, parentage verification, and forensic analysis.

Step 2: Detailed Explanation:
Let us evaluate both statements:
Statement (I) is correct.
STRs (Short Tandem Repeats), also known as Simple Sequence Repeats (SSRs), are repetitive DNA sequences where a short core motif is repeated in tandem.
The length of this repeating unit is typically very short, usually consisting of only two to six (often defined as two to four) nucleotide pairs (such as \( [GA]_n \) or \( [GATA]_n \)).
Because the number of repeat units varies highly among individuals, STRs are highly polymorphic.
Statement (II) is correct.
In molecular genetics, Short Tandem Repeats (STRs) are synonymous with microsatellites.
This distinguishes them from minisatellites (Variable Number Tandem Repeats, or VNTRs), which have longer core repeat units of 10 to 100 base pairs.
Therefore, both statements are correct.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are correct.