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LRs Considering Relatives as Alternate Contributors
Published in Jo-Anne Bright, Michael D. Coble, Forensic DNA Profiling, 2019
Jo-Anne Bright, Michael D. Coble
Assuming no inbreeding, the probability of a parent and their biological child sharing one allele IBD is exactly one. Therefore, given the first law of probability, the probability of a parent and their offspring sharing two or zero alleles IBD is zero. The probability of full siblings sharing one, two, or zero alleles is harder to visualize but may be seen using a Punnett square. Punnett squares are used to graphically represent the possible genotypes within offspring given the genotypes of their parents. A Punnett square given the parents (generation II) in Figure 5.1 is presented in Figure 5.2. There are four possible genotypes, and we can see their biological son is one of them (top right square). Assume that the parents give birth to a second son (not represented in the pedigree Figure 5.1). The possible genotype combinations for son number two are in Figure 5.2, each with equal probability of ¼. Assuming son number two is a 10,14 at this locus, the brothers would share one allele IBD: the 10. Similarly, if he was genotype 10,15, they would share two alleles IBD. If he was genotype 13,14, they would have no (zero) alleles IBD. And, finally, if he was genotype 13,15, they would share one allele IBD: the 15. Taken together, the probability of full siblings sharing two alleles IBD is ¼, one allele IBD is ¼ + ¼ = ½, and zero alleles IBD is ¼.
Genetic Principles
Published in Gail S. Anderson, Biological Influences on Criminal Behavior, 2019
Then, Mendel interbred this first generation, crossing Pp with Pp. Each parent donated one of two alleles to its gametes, either the dominant allele P or the recessive allele p. The following table (known as a Punnett square) shows all the possible combinations:
Patterns of Inheritance: Mendelian and Non-Mendelian
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Merlin G. Butler, Michael Begleiter, Shannon Lillis, Molly Lund, F. John Meaney
Most commonly, an individual affected with an autosomal dominant trait is the product of a mating between a normal parent and an affected parent. Students beginning their study of genetics learn to draw Punnett squares to help understand the segregation of genes in the egg and sperm. The Punnett square shown in Fig. 2 illustrates the possible results of the mating between a normal parent and an affected parent. The affected parent passes either the normal gene or the dominant disease gene to the offspring. The unaffected parent passes on a normal gene. Thus, there is a 50% chance of having an unaffected child with a homozygous normal genotype and a 50% chance of having an affected child with a heterozygous disease-causing genotype. When two individuals affected with an autosomal dominant condition conceive a child, there is a 1 in 4 or 25% of having a child who is homozygous for the disease gene. Typically, autosomal dominant conditions are more severe in the less common homozygous state than in the heterozygote state.
Women in science: a son’s perspective
Published in Journal of Neurogenetics, 2021
It does not matter if you are the president of the University of Toronto, a first-year undergraduate student, or a child entering their first day of grade school, my mom will treat you the same. I remember being about seven years old, sitting at a sushi restaurant with my mom. I asked her why some of my classmates look more like their mom or their dad. Smiling, my mom emptied what was left of my bento box, took salmon and cucumber rolls, and put them around the box. Moments later, she had me making Punnett squares with my sushi and bento box. At the time, I thought it was a great opportunity to play with my food. Now, I cannot help but think about independent assortment every time we eat sushi together. Each and every day, my mom walks a tight rope of how to communicate at the appropriate level and make the listener, often me, feel important and encouraged. Perhaps she gained this ability from her parents. Her father, Ernest, was a concentration camp survivor turned shoe salesman, with the equivalent of a grade five education. Moriah and I had the opportunity to spend our childhood with him and our Canadian-born grandmother Ruth, a former kindergarten teacher. Like our mother, we spent hours learning that Ernest’s inquisitive disposition and love of nature were second to none regardless of the horrific adversity he faced in his life and his lack of formal education. My grandmother Ruth instilled the qualities of patience, fairness, and the love of learning, in my mother, my sister and me. This unique upbringing may have helped my mom connect with and inspire us every day, just like she has inspired the diverse graduates at the University of Toronto during her convocation speeches.