Facebook and Apple ’s decision to offer distaff employee a $ 20,000 benefit to immobilize their nut argue a stunning disregard for the complexness of reproductive biota .
The Center for Genetics and Society write out anews releasethat name societal , technical , and biological business concern : the danger of block egg to both the fair sex and the individual that may one day arise from that egg , and contrary result that include infertility , cancer , and even death . I ’m recovering now from surgery to remove an 18 - pound ovarian vesicle , so I ’m specially sensitive to putter with ovaries in any way .
Marcy Darnovsky , PhD , executive theater director of the Center for Genetics and Society , summed up the magnanimous image beautifully , which deals with intent , not biology : “ Why are Facebook and Apple endorsing a proficiency that encourages their employees to put their wellness at risk ? pay for bollock freezing is being pose as a welfare for women , but it may be that discourage women from balancing work and menage is really a benefit to the companies . ”
I ’d like to bestow another layer to the discourse : we just do n’t recognise that much about why older egg run to finish up with a wrong number of chromosome . A terrific late enquiry report in theAmerican Journal of Human Geneticsaddresses exactly this issue : how do older bollock mis - kind their chromosomes ? I marvel if the egg - freezing advocates at Facebook and Apple read it .
Old Eggs
I always matt-up weird , as a genetic counselor , telling a womanhood older than 35 that she was of “ sophisticated maternal age . ” But back in the days of amniocentesis , before non - invasive antepartum testing became available circa 2012 , we did indeed consider these woman high - endangerment .
The “ maternal age outcome ” is real : ovulating eggs with extra or absent chromosomes ( aneuploidy ) does happen more frequently as a woman ages . The risk of infection of a charwoman carrying a trisomic fetus is 2 to 3 % if she ’s in her XX , but outgo 30 % if she ’s in her 40s .
But the advice of who should have amnio was more technical than biological : At years 35 , the danger of aneuploidy matched the risk of amnio being follow by miscarriage . Younger than that , in the absence seizure of a family history of aneuploidy , the risk of the procedure outweighs the endangerment of the problem . Although amnio risks fell precipitously over the years , for some reason that age of 35 remained a standard . ( Image : The maternal age effect for trisomy 21 Down syndrome )
In my text and classes , I ’d airily call the phenomenon the “ rotten egg theory , ” but it ’s technically term the “ production - origin speculation , ” an idea first hatch in 1968 by Alan Henderson and Robert Edwards , who pioneered in vitro fertilization . The hypothesis states that the oocytes that have been hanging around in the ovary the farseeing accumulate the most errors .
As my cyst , named Waldo , grew this retiring summertime , I had spate of opportunities to ponder the mysterious biota of the human ovary . The male of the species , not astonishingly , is simple : he begins fabricate spermatozoan at puberty and keep on to do so throughout life , without a monthly reminder of the process . A distaff starts making testicle when she herself is a 5 - month foetus . That means a pregnant fair sex holds the future ball that could become her granddaughters .
An Egg’s View of Fertilization
Just before birth , a female person has a million or so eggs stopped at a stage of meiosis ( the word form of cell division that makes gametes ) when the two chromosomes of each pair tend to wrap around each other and exchange component , a minuscule like two people hug and trading hats and knock . obviously , this crossing over is very authoritative for the power of each chromosome yoke to dust into separate cells as division continues .
An ovary caparison break eggs does indeed depend like aproduction line , with babe eggs enlarging and developing as they reach the periphery . An ovary is a little like a bag of microwave popcorn .
By pubescence , about 400,000 eggies remain in a womanhood ’s two ovaries . Each month , a few eggs awaken and take a few more tone in meiosis , halting at the very brink of chromosome pair separation , like 23 pairs of line up square dancers . At the mid - cycle hormone upsurge , the biggest egg pop out .
Ovulation ! The favourable female cell drops into the waving arm of a waiting Fallopian tube and propel towards the womb .
If a flack of sperm arrives and one dude penetrates the egg ’s membrane , the distaff cadre , at last , finish up meiosis . The egg then concentrates most of itself – cytol , organelles , nutrient — into one girl electric cell , along with exactly one written matter of each chromosome type . The puny other cell , a arctic eubstance , exits the body , its function to siphon off the second chromosome set while concentrating supplies for the fertilized egg . Unless dig into in a genetic exam , as aprevious postdescribed , the opposite trunk is flushed out .
If the egg escape a sperm ’s penetration , it too exits as the catamenial flow , meiosis bare . The female Hz may make us crampy and crabby , but biologically speaking , it is most elegant and not at all uneconomical , only fill out litotes when it make signified to do so .
Understanding Ovaries
In the study report in July , Terry Hassold , PhD , from Washington State University and colleagues admit a closer look at events in the human fetal ovary . And they discovered that one assumption of the product line of descent hypothesis , that the former eggs cross over less and that ’s why they may drop or add a chromosome , simply is n’t true .
The researchers used immunofluorescence microscopy to label proteins that score crossovers , examine 8,518 cell from 191 samples from ovary removed at 14 to 26 calendar week of gestation . The material came from elected abortions .
Results were surprising , view how entrenched the production short letter idea was .
The extent of crossing over varied , not greatly , between ovaries and even within ovaries . More significantly , the researchers happen no correlation between age of either the ballock or the woman and the extent of cross over .
“ If the production - line hypothesis were true , you ’d wait good deal of abnormal cells and you would expect them all to be happening late . We do see a pretty high relative incidence of abnormal cells , but they ’re just as likely to be pass early as later , ” first source and doctoral candidate Ross Rowsey say WSU News . The effect might not have show up in earlier study that deduce crossing over from cell conduct after nativity because that approach did n’t front at what was endure on in foetal ovaries .
The beauty of scientific enquiry is that when one hypothesis is disproven , investigators follow another . And in the case of the misjudged egg , another potential explanation is that the reasonableness for an surplus or missing chromosome is ebb levels with age of a protein called cohesin that , as the spellcheck - confounding name incriminate , glues chromosomes together , ease the exchanging of function . experiment from other species are now pursuing the cohesin surmise .
The expectant mental picture is that Facebook and Apple are attempt to give female employees to undergo a very risky procedure with not - well - understood consequences , when we do n’t even be intimate the mechanics behind the maternal age effect . Has n’t the current Ebola crisis teach us not to ignore biology ?
This articleoriginally appearedat PLOS Blogs ’ DNA Science Blog and is republished here under a Creative Commons Attribution 3.0 Unported License .
Top image : ICSI .
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