Chapter E, Problem 1P

What is CODIS? Describe the four most important feature of gentic markers used in the system.

Summary Introduction

To analyze:

Describe CODIS and the four most important characteristics of genetic markers used in this system.

Introduction:

In $\text{1990}$, the United States Federal Bureau of Investigation created national DNA database known as Combined DNA Index System (CODIS). This database is preserved by Federal Bureau of Investigation. It has three levels of information – Local DNA Index System (LDIS), State DNA Index Systems (SDIS) and National DNA Index System (NDIS)

Explanation of Solution

CODIS – The United States national DNA database is Combined DNA Index System. Federal Bureau of Investigation (FBI) formed it and preserved it. Depending on the type of information being searched against, the CODIS software contains multiple different databases. These databases include forensic samples collected from crime scenes, missing persons, etc.

The genetic markers used in forensic genetic analysis are short tandem repeats (STRs) which contain different numbers of copies of short, repeating sequences of DNA. STRs are less than ten base pairs long and follow a co-dominant pattern of inheritance.

There are four important features of genetic markers – STRs used in CODIS. These include –

1. A CODIS STR must have a known location of chromosome and the location should ensure that the STR follows independent assortment from all other CODIS markers. This is important for calculation of individual identity.

2. A CODIS STR must have multiple alleles in all examined populations. The allele should not a frequency more than twenty to twenty five percent in a population. This increases the effectiveness of individual genetic identification.

3. A CODIS STR must carry alleles that can be amplified by PCR consistently, reliably, and accurately. These alleles should be such that they can be analyzed in highly automated laboratory settings in specially equipped laboratories. This is required to minimize the risk of contamination of DNA samples and to ensure the reproducibility of the results.

4. The last criterion for CODIS STRs is that their PCR products must distinguish alleles from one another clearly enough for automated PCR amplification and gel electrophoresis. This is required for reliable identification of each allele.

Conclusion

CODIS is an important software, containing different types of databases which are used for the forensic investigation.