Prime_Time_spring_2019

DNA Matters Tim Kozelsky | DNA & Data Service Analyst | tkozelsky@akaushi.com AKAUSHI BREED GENET ICS

H e’s the daddy … until he’s not! My column in this issue will focus on the DNA parenting verifica- tion process we follow when DNA is submitted. When does a calf qualify as Akaushi sired? Why didn’t a calf qualify to

are typically expressed as AA, AC, CC, etc. These results are synonymous with homo- zygous and heterozygous traits such as polled, F11 and coat colors. Right now, there are more than 200 markers that make up an SNP parentage profile, and there are tests capable of looking at more than 250,000 markers for certain genetic tests. There are many advantages to SNP. Par- entage determination has a much higher degree of accuracy. Individual trait carri- ers can be identified. Expected progeny differences can be greatly enhanced. The disadvantage is that a good DNA sample is needed in order to extract the amount of DNA material needed to create the profile.

any sires? What does it mean when we say a calf qualifies to a sire and/or a dam, but the mating doesn’t work? I hope to clarify questions people have about the verification process. So, how does DNA work? First, we have to understand how the profiles for the two DNA methods we use – STR and SNP – are derived. Short tandem repeat (STR) looks for particular sequences of markers within a strand of DNA. The results are expressed numerically, such as 17/180, 146/150, 87/87, etc. These markers, or STR loci, are deter- mined by the International Society of Ani- mal Genetics (ISAG). The positives of using STRs is that it is very easy to generate a profile, which makes it very favorable in forensic investi- gations where the amount of DNA available could be very minimal. The concerns are that it is also very susceptible to contamina- tion in that the DNA can be influenced by any other DNA source the sample may have come in contact with. Also, the DNA profile only consists of 10-12 markers, so the ability for discrimination or complete identification of a particular parent may not be possible. There may not be enough differentiation be- tween the STR profiles of two sires to deter- mine which the actual sire is. The newer method the industry has ad- opted is called single nucleotide polymor- phisms (SNP). It looks at the value of each nucleotide base. These bases contain one of four values: A for adenine, C for cytosine, G for guanine and T for thymine. The results

Parentage is called an exclusionary pro- cess in that all possible parents are consid- ered until they can be excluded. Regardless of which method is used, DNA markers are always pairs in which one is from the moth- er and one is from the father. An example would be if an offspring had an STR profile in which allele TGLA had a value of 81/97. The verified parents have the following values for the same marker: sire 81/91 and dam 91/97. In this case, the offspring got the 97 value from the dam and the 81 value from the sire.

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Akaushi Prime Time • Spring 2019

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