Question

Why were VNTR sequences replaced with STRs for obtaining a DNA profile?

Short answer

VNTR sequences were replaced with STRs for obtaining a DNA profile due to their accuracy, easier analysability, and ability to be amplified using PCR, which allows profiling from small, degraded DNA samples.

Step-by-step solution

Understanding VNTR and STR

It is important to first understand what VNTR and STR means. VNTR stands for Variable Number Tandem Repeats and STR stands for Short Tandem Repeats. They both are part of DNA sequence and repeats multiple times.

Comparing VNTR and STR

VNTRs are longer segments of repeated DNA with the repeat unit consisting of 10 to 100 base pairs. On the other hand, STRs are shorter segments of repeated DNA with the repeat unit typically consisting of 2 to 6 base pairs. Because of their shorter length, STRs are less likely to undergo recombination or fragmentation which allows them to provide more reliable results.

Reasons for shift from VNTR to STR

The significant reasons for replacing VNTR sequences with STRs for obtaining a DNA profile include: STRs are more accurate, they are easier to analyse with current technology, and they can be amplified using the technique of Polymerase Chain Reaction (PCR) making them suitable for profiling even small, degraded DNA samples often found at crime scenes.