DNA Ladders


DNA Ladders
  • Hind III DNA marker
  • PST I DNA marker
Bacteriophage lambda DNA was used. Molecular weight 48.5kb of genomic DNA. Hind III gaston was carried and then restriction with PST 1 was performed.

In both cases, different molecular weight fragments were formed which by running gel were used as markers. Later, more fine fragments came using her enzymes. Similarly, protein markers were formed by putting all proteins of different molecular weights in one tube. Likewise, markers forensics are finer.

The combined DNA Index System (CODIS) uses 13 STR sites. We can make our own markers by amplifying all 13 STR sites, running on el purifying them, and by comparing it with some marker as the molecular weight will be compared. So by putting them on gel.markers of known molecular weights. These can be used as DNA Ladder.


Much bands/markers that have up to 100-500 bp fragments are required. Not bigger fragments like 500 or above. The difference of 3-4 nucleotides can be seen with the help of these markers. For example, in the case of VIVA, if there is a mnge of -5-10 then fragments for 5,6,7,8,9,10 should come. Markers should be finer for it: there should be markers for all possible alleles.

Amelogenin is a site on the X chromosome, on the basis of which gender can be discriminated against. It also contributes to teeth enamel. There is a deletion of 6 bp on the X chromosome. e.g. y chromosome will give 112bp of amelogenin, in X the fragment will be of 100bp. Thus if in a sample two peaks are obtained then it belongs to a mole.


In a female sample, a single peak is obtained, product size or peak height will be more as it will be producing more. In the case of a sexual assault case, there will be mixed samples.


Through the ladder, size can be identified. There may be a problem. For example, as in the Indian population, there is a deletion in both or not in both. As a result, there will be one product; no differentiation.

As the y chromosome is different from x thus there might be some other site as well.

  • In first-generation multiplex PCR, the SIR sites used have the power of discrimination 1 in 10,000. 4 SIR sites were used:

TH01 VWA
FES/FPS F13A1

  • Ability to identify 1 person out of 10,000.


Second generation Multiplier (SCOM):
  • It was claimed to have the power of discrimination 1 in 50 million 6 SIR sites were used:

TH01 FGA D18S11
VWA D8S1179 D21S11

In use is the 13 CODIS System.

D3S1358 TPOX CSFIPO LPL
F13B THOI F13A01 FES/FPS
FGA D5S818 D7S820 D8S1179
D13S317 D21S11 D16S539 D18S51

  • The purpose is to reach the individual out of the population.
  • New sites can also be used, some can be removed.

Editor's Recommendation:

DNA Ladders DNA Ladders Reviewed by AB Ultimate Guides on June 19, 2020 Rating: 5

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