Y CHROMOSOME ADAM
Males have an X and a Y chromosome plus 23 pairs of chromosomes that are found in both sexes. Females have two X chromosomes. The X and Y chromosomes are called sex chromosomes. The Y chromosome is not essential for life (any female is living testimony to that inference). But it sure is needed to make a male. The Y chromosome has a gene that converts a neutral embryonic future sex organ (the gonads) into testes. The testes then make hormones that produce the male sexual apparatus. The absence of that gene on the Y normally occurs when the fertilized egg has two X chromosomes and the gonads become ovaries and the absence of the male hormones lead to female sex apparatus formation. Sometimes gene mutations can mess things up leading to XY females or apparent XX males.
The Y is found in half of a male’s sperm. Those are the sperm that produce sons. The X is found in the other half of the male’s sperm and they produce daughters. Biologists know that it is the male who determines the sex of his children but for generations many women were punished for not giving husbands sons!
The genes of the Y stay together but the genes of all other chromosomes have an opportunity to switch bits of their chromosomes when sperm or eggs are made. Since fathers pass their Y chromosomes only to their sons and these genes always stay together, the mutations that arise in the Y chromosome will stay there unless they lead to infertility. That is not at all unusual because many genes for making sperm are found on the Y chromosome.
The sequence of most of the genes for our Y chromosome is known because it is a small chromosome. Samples from people around the world in different continents have been studies and there is no variation except in Africa! Perhaps larger samples will reveal some differences, but the rate of change of normal to mutant is relatively low compared to some other genetic systems in our cells. This implies that our common Y ancestor or Ur-grandfather (whom we call Y chromosome Adam) left his African homeland with his mitochondrial Eve partner about 250,000 years ago and none of his European, Asian, or New World descendants have established Y chromosome variations that survived.
Just as mitochondrial Eve, our common ancestor of humanity, had kin in the thousands, so too Y chromosome Adam had lots of male kin. They just didn’t luck out to get their Y chromosome to us. When we study pedigrees, we often note people who keep following their family name back. They are following their father’s Y chromosome as far as it goes. Thus J. Pierpont Morgan, the financier and T. H. Morgan the Nobel Prize geneticist, share both a common last name, a relative who stepped off the Mayflower, and a common Y chromosome. They share very few of their other genes from that Mayflower ancestor.
Showing posts with label geneology. Show all posts
Showing posts with label geneology. Show all posts
Friday, December 17, 2010
Saturday, December 11, 2010
Life Lines 77
WELCOME TO MAXWELL HAWKINS CARLSON, AMERICAN
My ninth grandchild arrived June 22, 1998 in Pasadena, California. I was visiting my closest friend, Dr. Peter Gary, a composer in Victoria, British Columbia. He is a Holocaust survivor and had studied with Kodaly and Bartok. My wife, Nedra, was already en route from Vancouver to Los Angeles when baby Maxwell arrived a week early. His mother, Lyn Yasumura, MD is an obstetrician and this was her first child although she has delivered over a thousand babies for other women. His father, Anders, is finishing his Ph.D. in structural engineering at Caltech. Anders and Lyn attended Ward Melville High School in Setauket.
Baby Maxwell, you are my mother’s 52nd descendant. She was born in Bound Brook, New Jersey of immigrants from Tarnapol, in what is now the Southwestern Ukraine. You are my father’s 17th descendant. He came from Stockholm, Sweden and settled in New York City after a few years in the merchant marine. You have eight cousins on your father’s side and none yet on your mother’s side. You are a melting-pot American who combines Swedish (one-eighth) Japanese (one fourth), Ukraine (one eighth), German (one fourth, English (one tenth), Welsh (one percent), Scottish (one percent), and French (a trace) ancestry. Your ancestors are Lutheran, Baptist, Jewish, Huguenot, Catholic, Unitarian, and Buddhist.
Four living relatives also have your Y chromosome. Three relatives have your mitochondria. You have about 100 genes (out of 25,000) of your ancestor, Andrew Babcock, who helped make the links of the great chain that stretched across the Hudson River near West point to prevent the British navy from supplying its Canadian forces during the Revolutionary war. Seven generations ago, your ancestor, Israel Dock Johnson, fought for the Union during the Civil War with his Indiana regiment and he survived the rigors of a Confederate prison camp by digging up and eating raw sweet potatoes. You have about 400 of Dock Johnson’s genes. One of the slaves freed during the Civil War was the grandfather of Evelyn [Billie] Hawkins, whose last name is now your middle name. She was your father’s fifth grandparent and she had adopted our family before your father was born.
You bring together by your birth, four very different families. Your Japanese-American grandfather, a professor and physiologist, was American-born and raised in New York and California until World War II when he was sent with his parents to an internment camp in Idaho. Your maternal grandmother, a college administrator, was born and raised in New York of German-Americans whose ancestors lived many generations in Virginia. Your paternal grandfather, a professor and geneticist, grew up in the slums of New York. Your paternal grandmother, an in-vitro fertilization embryologist, grew up in the small towns and farms of Northern Indiana. What we all have in common is our designations as Americans.
From yesterday’s immigrants to those who have lived in North America for a dozen or more generations, we have enjoyed the benefits of freedom (sometimes denied) and opportunity (sometimes thwarted). Enjoy that good fortune, Maxwell, and celebrate the many components of your ancestors who each helped make America the world’s most admired concept.
My ninth grandchild arrived June 22, 1998 in Pasadena, California. I was visiting my closest friend, Dr. Peter Gary, a composer in Victoria, British Columbia. He is a Holocaust survivor and had studied with Kodaly and Bartok. My wife, Nedra, was already en route from Vancouver to Los Angeles when baby Maxwell arrived a week early. His mother, Lyn Yasumura, MD is an obstetrician and this was her first child although she has delivered over a thousand babies for other women. His father, Anders, is finishing his Ph.D. in structural engineering at Caltech. Anders and Lyn attended Ward Melville High School in Setauket.
Baby Maxwell, you are my mother’s 52nd descendant. She was born in Bound Brook, New Jersey of immigrants from Tarnapol, in what is now the Southwestern Ukraine. You are my father’s 17th descendant. He came from Stockholm, Sweden and settled in New York City after a few years in the merchant marine. You have eight cousins on your father’s side and none yet on your mother’s side. You are a melting-pot American who combines Swedish (one-eighth) Japanese (one fourth), Ukraine (one eighth), German (one fourth, English (one tenth), Welsh (one percent), Scottish (one percent), and French (a trace) ancestry. Your ancestors are Lutheran, Baptist, Jewish, Huguenot, Catholic, Unitarian, and Buddhist.
Four living relatives also have your Y chromosome. Three relatives have your mitochondria. You have about 100 genes (out of 25,000) of your ancestor, Andrew Babcock, who helped make the links of the great chain that stretched across the Hudson River near West point to prevent the British navy from supplying its Canadian forces during the Revolutionary war. Seven generations ago, your ancestor, Israel Dock Johnson, fought for the Union during the Civil War with his Indiana regiment and he survived the rigors of a Confederate prison camp by digging up and eating raw sweet potatoes. You have about 400 of Dock Johnson’s genes. One of the slaves freed during the Civil War was the grandfather of Evelyn [Billie] Hawkins, whose last name is now your middle name. She was your father’s fifth grandparent and she had adopted our family before your father was born.
You bring together by your birth, four very different families. Your Japanese-American grandfather, a professor and physiologist, was American-born and raised in New York and California until World War II when he was sent with his parents to an internment camp in Idaho. Your maternal grandmother, a college administrator, was born and raised in New York of German-Americans whose ancestors lived many generations in Virginia. Your paternal grandfather, a professor and geneticist, grew up in the slums of New York. Your paternal grandmother, an in-vitro fertilization embryologist, grew up in the small towns and farms of Northern Indiana. What we all have in common is our designations as Americans.
From yesterday’s immigrants to those who have lived in North America for a dozen or more generations, we have enjoyed the benefits of freedom (sometimes denied) and opportunity (sometimes thwarted). Enjoy that good fortune, Maxwell, and celebrate the many components of your ancestors who each helped make America the world’s most admired concept.
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