Evolution is a Fact #7 - Human Egg Yolk Gene
Exploring the human genome is like roaming around an historic town. Some places are pristine and obviously still in everyday use. Others have been unused for a while and starting to show signs of decay and if you look carefully there are relics of buildings that were abandoned long ago.
In this post we are going to look at a gene that we still carry in every cell in our body but which fell into disuse 10s of millions of years ago.
Humans are placental mammals. We nurture our young in the womb for a long time and then feed it with milk for a relatively short period. Marsupial mammals have much shorter pregnancies but they lactate for longer. There is a third group known as the monotremes which consists of just the duck-billed platypus and four species of echidna. The reproductive strategy of this has not changed much from their amphibian ancestors. They lay eggs filled with yolk and then feed their young with milk that is secreted onto a patch of skin.
The major nutritional ingredient in egg yolk is a protein called vitellogenin. Geneticists decided to have a look at the genes for this protein in chickens and then see if it still existed in mammals.
The first task was to locate vitellogenin in the chicken genome. They discovered chickens have three copies of this gene. Next they identified genes that were physically located either side of vitellogenin on the same chromosome. Next they located these active genes in the mammal genomes. When they examined the region that lay between these genes they found a genetic relic that was millions of years old.
In monotremes they found one active copy of the gene but in placental and marsupial mammals all three were inactive relics or pseudogenes.
When they studied the sequence of code for these broken genes in humans and in primates they found exactly what evolution predicted. Precisely the same mutations had occurred in the very same places in our closest relatives.
They were further able to show that the production of milk predated the switching off of our final vitellogenin by at least 100 million years.
The existence of the genetic machinery for yolk production is irrefutable evidence for our distant evolutionary history.
Part 1 - Protein Functional Redundancy ... Part 4 - Smelly Genes Part 2 - DNA Functional Redundancy ... Part 5 - Vitamin C Part 3 - ERVs ... Part 6 - Human Chromosome 2
Wouldn’t it be easier to just refer people to the book or books you are lifting this stuff. This forum isn’t a biology class. You are taking credit for ideas and research that isn’t your own.
Hello again Clambake. I am very impressed by your dedication to my "Evolution is a Fact" series. I am planning on 50ish threads in the series so I hope you keep up.
I am really not taking any credit at all for anything I post in these threads. I am just an amateur who enjoys reading science stuff and explaining it.
If you go to google scholar and type in "vitellogenin pseudogene" you will find lots of source material for further research.
By the way if calm down and don't punch the keys so hard you won't get those double posts.
Instead of giving out bible studies no one wants you have chosen to flood this board with science lessons we didn’t ask for.
A life wasted is a life wasted.
A life wasted is a life wasted
I am flattered you think these posts are so substantial. They are all stuff I know so it doesn't take me very long to write them up.
By the way I never plagiarise. Everything is my own words based on research in multiple sources. I can recommend a reading list if you like?
I like these posts, keep them coming.
no one wants you
Just out of interest Clambake, you can only speak for yourself. Your assertion above is I think a gross exaggeration. If you don't want to read this stuff that Cofty has chosen to "flood" this board with then don't bother to read it. I for one find it fascinating and welcome any and all posts to come on the subject. Thanks Cofty!
I find your lessons a bit hard to follow (ie, lots of information in a small package - well done), so have been supplementing by googling and rounding them out. I've never had much interest in the actual science of evolution before, so you have sparked that. Thanks. I do have a question about this lesson, just a small one.
My reading showed that 'joeys' are nursed for 350 days, and humans also breast-feed for at least a year (under normal conditions, ie, before industrialization and other factors gave women the option to refrain from breast feeding). This short term of breast feeding is a 20th century practice, and has little to do with women's ability to produce milk for years after birth.
The practice made popular in the 1950s, of feeding infants Pablum (ie, cereal grains) beginning at 3 months is now known to be a bad nutritional start. Mother's milk is all that is required, and indeed, it is recommended that 12 months be the earliest cutoff (medically) for breast feeding, even when the child's diet is already inclusive of other foods.
Are we (modern technological culture) effecting an eventual biological change, by rejecting 'nature' and turning to substitution for mother's milk? In other words, will we 'lose' the ability to lactate, as more generations of babies are not fed from the breast? In effect, 'use it or lose it'?
And I don't expect a 'defining answer' ... it just made me think of all the messed-up, unnatural things we are doing to ourselves and the planet, and left me wondering what kind of genetic changes may take place down the road. Or perhaps I have just read too much sci-fi in my life (not a bad thing, considering Verne and others who 'imagined' the future). : )
Interesting question talesin.
Genes are only preserved without damage if there is a selective pressure. On the other hand our very large gene pool and modern travel probably makes it unlikely that any particular allele is going to gain much traction.
Did you know that men also have all the machinery for breast feeding?
One thing I plan to do if I ever am able to retire is take a college course on Biology. This stuff is so fascinating to me now. Couldn't care less when I was 14.
Thank you Cofty for the time and effort you put into this thread, you make JWC an interesting place to keep up with.