In other words, let's say Xena and Stevie have litter #1 consisting of puppies A, B, C, D, and E. Xena and Stevie reproduce with each other again, and out pops litter #2 consisting of puppies F, G, H, I, and J. Is puppy A genetically closer related to puppy B than she is to puppy F? Is puppy G closer related to puppy J than he is to puppy D?
@gentlesheepman So, "relatedness" as measured by DNA testing for parentage typically looks at short tandem repeats (STRs, = "microsatellites"). These are segments of non-coding DNA, which means that they do not determine physical traits or physiological function. They are more or less "filler" DNA in between the important coding stuff, but since they are heritable and unique to an individual can be used to identify relatedness. If tested by DNA, all offspring from a set of parents would exhibit a set of these alleles inherited from their parents. In the most simple terms, they are all the same "relatedness".
Anyway, genetics and inheritance are much more complicated than just "take 50% of Mom's DNA and 50% of Dad's DNA and put them together to get one possible offspring. There are many factors that contribute to diversity of offspring even from the same parents - epigenetics on parental DNA, meiosis and crossing-over, epigenetics on offspring DNA, and erroneous processes like mutations and translocations.
The NCBI NIH Genetics Home Reference and CDC Genetics guides are great places to learn more! There is simply too much to cover in a single Reddit comment.
@devonboy We learned it in my biology class. The parents provide the same DNA, but when they have a child it’s a roulette as to what mix of genes they get. So siblings share 50% of the similar strands and patterns. Like how both sibling have brown hair, but one has blue eyes and the other green. They share the brown hair gene but when it comes to eyes, they got a different combo. It’s how/why parents can have 20 kids and not have two children who are super similar genetically.
@devonboy There are only two sides to the strand of DNA for each gene. Overall, 50% of the siblings’ DNA is similar. They can look totally different, a lot of that DNA is for internal stuff that is similar in families, like blood type or heart disease likelihood, stuff we don’t see. It’s always going to be a huge roulette wheel as to what the kids get, but 50% will be similar because they come from the same parents who provide the same DNA options, just in different combinations.
@imagebeastmarkbeast I'm getting downvoted, but this article you linked literally confirms what I said.
Mom passes one of two copies for each of her genes onto an offspring. Theoretically, she could pass one copy of each of her genes to one offspring and the other copy of each of her genes to another offspring. Siblings that share both parents will on average share 50% of their DNA, but it isn't horribly unlikely that one pair of siblings from the same litter will only share 30% of their DNA while another pair of siblings from that litter will share 65% of their DNA.
@devonboy The challenge is trying to tell twins from siblings that look like each other. I mean how would you know if any two pups in a Golden litter are twins?
One thing that is interesting is how some markings are shaped by cell division and cell actions while the embryo is developing. I remember seeing photos of identical twin horse. They both had the genes for a blaze but the actual shape of each horse's blaze was different. And the same for their socks. So they were identical twin horses genetically but not identical phenotypically.
@tippymoondawg That is always interesting to me. If you had Merle twins, they would be Merled completely differently for instance because it’s random deletion and nobody would ever know.
