Pls/tia, explain genetics to me - closest cousins/siblings with differences?

[UTUSN]

My mother's brother married my father's sister. I have thought of my "double cousins" as genetic siblings for all practical purposes. Which at my level translates into "identical."

Most of us have done the DNA fad thing, and while most of the results are largely similar there are a couple of significant differences. The senior double cousin, who is also a Fundie and Drumpfster (no, I don't attribute those to DNA), takes pleasure in explaining that "each parent contributes 3 markers, meaning 6 different ones, and God rolls the dice, so even siblings can be different."

Lounge can explain it better, have at it.

[Ocelot II]

1. Here's a good explanation.

https://genetics.thetech.org/ask-a-geneticist/same-parents-different-ancestry

The only relatives who will ever have exactly the same DNA are identical twins because they came from the same fertilized egg that divided after fertilization.

[UTUSN]

2. Excellent article, sounds same as my cousin's explanation "Gawd rolls dice" - am (trying to) digest

But then, I have trouble with Time Zones and Standard/Savings. And don't get me started on GMT!1

No, really, thanks. Will study the link.

[UTUSN]

3. So my "double cousins" are just as randomly related to me as anybody else?

[unblock]

4. We have that in our family as well

We call them "criss-cross cousins". I'm one generation off as in my case it was my grandparents whose corresponding siblings married. At a double wedding in fact.

Typical first cousins involve one pair of siblings and two "random" people. The situation we're talking about involves only two sibling pairs. So the parents are drawing from two genetic pools instead of three.

So you are more closely related, genetically, to your criss-cross or "double" cousins.


But not as closely related as your siblings and certainly nothing close to identical.

[UTUSN]

6. You got me closer to getting it.

[wnylib]

10. No. They are more closely related to you

than just some random person, just not identically matched in DNA.

Example from my father's family. His maternal grandmother was English and Seneca. His maternal grandfather was English and Mohawk. So my father's mother was English, Mohawk, and Seneca. Her Native ancestry was visible in her appearance, more so than in her mother. Her sister (my father's aunt) had the same ancestry, but looked much more Native, as if she had no English ancestry at all.

Then my father's mother married a man whose ancestry was German and Native (unidentified Algonquian tribe). They had 9 children. One had blue eyes, very fair skin, and very light brown hair. Did not look like she had any Native ancestry at all. 4 looked Native, as if they had no European ancestry. The rest looked like a mix. You could tell that they had both Native and European ancestry. A couple if them, including my father, had blue eyes with their black hair.

It all depends on which genes from each parent a child gets. Not all the children get the same genes from each parent, even though they get half from each one. This is evident in any white family, where there are differences in hair and eye color.

My blue-eyed, black-haired, racially mixed father married a blond, brown-eyed daughter of German immigrants. They had 4 children. My oldest brother and I had the same coloring - dark brown hair, brown eyes, medium to fair skin tone. My sister got my mother's blond hair and brown eyes, but had my father's high cheekbones. My other brother got my father's blue eyes and mother's blond hair.

I have cousins with very light hair and skin, and blue eyes. I also have cousins with black hair, blackish brown eyes, and light brown to dark beige skin.

I have Native traits that are not visible to most people, e.g. "shovel" teeth and broad, high arched feet. I also have an eyelid fold associated with Asians and some Native Americans, but not as pronounced in me. But, I have my mother's blood type and tendencies to allergies and asthma.

Every genetic mating between a mother and father produces a roll of the dice in which genes from each one gets passed on to the child.

[hunter]

9. Curiously, identical twins are not identical.

Identical Twins' Genes Are Not Identical

Twins may appear to be cut from the same cloth, but their genes reveal a different pattern

Identical twins are identical, right? After all, they derive from just one fertilized egg, which contains one set of genetic instructions, or genome, formed from combining the chromosomes of mother and father.

But experience shows that identical twins are rarely completely the same. Until recently, any differences between twins had largely been attributed to environmental influences ( otherwise known as "nurture" ), but a recent study contradicts that belief.

Geneticist Carl Bruder of the University of Alabama at Birmingham, and his colleagues closely compared the genomes of 19 sets of adult identical twins. In some cases, one twin's DNA differed from the other's at various points on their genomes. At these sites of genetic divergence, one bore a different number of copies of the same gene, a genetic state called copy number variants.

--more--

https://www.scientificamerican.com/article/identical-twins-genes-are-not-identical/

Genetics is a lot messier than we once thought.

The analogy of genomes as static "blueprints" that are occasionally revised by beneficial mutations and natural selection isn't a good one.

Genomes are more like a huge blueprint made entirely of Post-it notes, layers and layers of them, many firmly fixed and strongly conserved in reproduction, others less so. Sections of DNA can be duplicated or deleted. They can change their positions. The expression of a particular gene can be suppressed or enhanced. Etc.

[UTUSN]

11. "a lot messier" - yea, I know *I'm* getting more confused than I was to begin with!1

[Scrivener7]

5. My father's brother married my mother's sister! It's great to have those double cousins, isn't it?

Very simplistically, for each trait, you inherit one allele from each parent. Your father and mother each inherited one allele from each of their parents.

So your father has two alleles for eye color. But you only inherit one of those. Likewise with your mother.

So (also a very simplistic high school level explanation) my mother had two green eyed alleles: gg
My father had a brown allele from his father and a green allele from his mother. His eyes were brown: Bg
I received a green allele from my mother and a green allele from my father: gg

Our two families have similar facial structures, but my family are all green or brown eyed and red haired, and my cousins are all blue eyed and dark haired.

[UTUSN]

7. "great" - well, my double is a Fundie/Drumpfster, so...

But the rest of your post is fascinating!

[Scrivener7]

8. I have one of those, but fortunately there are 4 others.