Heritage Album

family tree dna?

do brother and sister have the same dna say there two sister two brother do they all have same dna? also if the family and another family have a baby together what are the results like brother and sister

Public Comments

1. A brother and sister share (statistically speaking) 50% of the same DNA. Each one gets 23 chromosomes from each parent out of each parent's 46 chromosomes. So odds are that 50% of your DNA is the same as a sibling's DNA. Of course, this is simplified to not include crossing-over. The only siblings that share 100% identical DNA are identical twins.
2. Full brothers and sisters have between 1/4 and 1/2 their dna in common (depending on how you calculate that). It's virtually impossible for 2 siblings to have the identical DNA (except identical twins). In the case of a brother and sister, it's obvious they have different DNA, because one is a boy and the other a girl! I don't understand the second question.