Why are non-coding repetitive sequences used for DNA fingerprinting?

Non-coding repetitive sequences are used for DNA fingerprinting for several reasons:

1. Variability: 

Non-coding repetitive sequences, such as variable number tandem repeats (VNTRs) and short tandem repeats (STRs), tend to be highly variable among individuals. These regions of the genome accumulate variations in the number of repeated units, creating unique genetic profiles. This high variability makes them ideal for distinguishing individuals.

2. Inheritance: 

Non-coding repetitive sequences are typically inherited in a Mendelian fashion, meaning they are passed down from one generation to the next. This heritability allows for the establishment of familial relationships and paternity testing.

3. Abundance: 

Non-coding repetitive sequences are abundant in the human genome, offering numerous potential loci for analysis. Their abundance allows for the creation of complex and highly individualized DNA profiles.

4. Lack of Functional Constraints: 

Non-coding repetitive sequences do not code for proteins or play a direct role in gene function. This lack of functional constraints means that mutations in these sequences do not typically lead to harmful effects, making them suitable for genetic analysis without the risk of disrupting essential biological functions.

In contrast, coding repetitive sequences, if used for DNA fingerprinting, may not be as variable because mutations in coding regions can have significant consequences for gene function and could be subject to stronger selection pressures. Therefore, non-coding repetitive sequences are preferred for DNA fingerprinting because they provide the necessary variability and do not impact essential biological processes.

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