Half-Sibling Test

A half-sibling test is a DNA test that determines if siblings share only one parent (mother or father), i.e., if siblings share only one parent in common (i.e. same father, different mother, or vice versa). This test determines if siblings share only one parent by looking for DNA matches.

Characteristics of half-sibship sibling testing

In a half-sibling test, siblings may share 50% of their DNA. This means there is a lower genetic match than in full-sibling tests (where both parents are shared), and the results can be more difficult to interpret than full-sibling tests.

Methods for half-sibship sibling identification

The main technologies used are:

1. STR (short sequence repeat) analysis

• STRs are repeating sequences in DNA that have different patterns for each individual. STR analysis compares how many STR markers match between siblings to confirm blood ties.
• Half-siblings: If they share one parent, they will likely have a match of about 25%-50% of the STR markers.

2. SNP (single nucleotide polymorphism) analysis

• SNP analysis is a method to check the genetic identity between siblings by analyzing the difference between a specific single nucleotide. Although the matching rate is lower for half-siblings compared to full-blood siblings and parent-child relationships, it is still useful for checking blood ties.

Steps for testing for half-sibling relationships

1. Sample Collection:

• Saliva and cheek cells (buccal swab) will be collected from each sibling.

1. Sample delivery:

• The collected sample will be sent to a testing institution.

1. DNA analysis:

• DNA is extracted at the testing facility and SNP and STR markers are analyzed. In the case of half-related siblings, precise analysis is required because there are not as many markers that match as in full-related siblings.

1. Results:

• The percentage of DNA match and the probability of sharing a parent will be reported. Half-siblings will usually report a match rate of less than 50%.

Uses of half-sibship sibling testing

• Half-sibling relationship verification: Used to verify the relationship between siblings who may have half-siblings, for example.
• Inheritance and legal issues: It can be used in inheritance or legal situations where you need to prove a sibling relationship.
• Family Relationship Verification: Used to verify blood ties when family background is unknown.

Benefits of half-sibling testing

• High accuracy: DNA analysis is highly accurate, and by using STRs and SNPs, it can accurately determine whether or not people are half-siblings.
• Non-invasive: Collecting samples from saliva or oral swabs is painless and easy.
• Can be used for legal proof: Useful when legal proof is required, such as in inheritance or custody issues.

Restrictions on half-sibling testing

• Uncertainty when parental samples are not provided: When parental DNA samples are not provided, it can be difficult to determine the relationship between siblings, especially if the father is unknown. Having parental samples increases the accuracy of the test results.
• Results are difficult to interpret: Because the genetic match rate is lower than for full siblings, determining whether or not a person is half-sibling may require more testing and interpretation of the results.

Interpretation of the results

• A match rate of 25% to 50% indicates that the two are half-siblings who share only one parent. In particular, if the match rate of STR markers falls into this range, it is presumed that the two share one parent.
• Low match rate: If the match rate is low, it may be that they are unrelated or have completely different parents.

Conclusion

Half-sibling testing is a reliable DNA test to determine if siblings share only one parent. It is especially useful for determining the relationship between siblings who share only one parent, such as in inheritance issues or family verification. This test can confirm genetic ties with high accuracy and is an important tool for understanding family connections.