The results shown are from a DNA test for four genes used in a paternity identification case. DNA for the mother (M) and her child (C) are shown along with DNA from two possible fathers, F1 and F2. What can you conclude based on the DNA results available?

Verified step by step guidance

1. Step 1: Understand the principle of paternity testing, which is based on the fact that a child inherits half of their DNA from the mother and half from the biological father. For each gene locus, the child's alleles must be a combination of one allele from the mother and one from the father.
2. Step 2: For each gene tested, compare the child's alleles with the mother's alleles to determine which allele the child inherited from the mother. The remaining allele(s) in the child must have come from the biological father.
3. Step 3: Compare the paternal alleles required (those not inherited from the mother) with the alleles present in each potential father (F1 and F2). For a man to be the biological father, he must have at least one allele matching the paternal allele at each gene locus tested.
4. Step 4: Identify any gene loci where a potential father does not have the required allele to match the child's paternal allele. If a potential father lacks the necessary allele at any locus, he can be excluded as the biological father.
5. Step 5: Based on the allele matches and exclusions, conclude which potential father is consistent with the child's DNA profile and therefore most likely to be the biological father.

Key Concepts

Mendelian Inheritance and Allele Matching

Mendelian inheritance explains how offspring inherit one allele from each parent for a given gene. In paternity testing, the child's alleles at each gene locus must match one allele from the mother and one from the biological father. This principle allows exclusion or inclusion of potential fathers based on allele compatibility.

DNA Profiling and Genetic Markers

DNA profiling uses specific gene loci with known variations (genetic markers) to compare individuals. These markers are highly polymorphic, making them useful for identifying biological relationships. Matching patterns between child and potential fathers at multiple loci increase confidence in paternity determination.

Paternity Exclusion and Inclusion Criteria

Paternity exclusion occurs when a potential father's alleles do not match the child's alleles at one or more loci, ruling him out as the biological father. Inclusion requires consistent allele matches across all tested loci, supporting the possibility of paternity. This concept is critical for interpreting DNA test results in legal cases.