Notices
Results 1 to 9 of 9

Thread: X sex chromosome gametes: Why do they result as sperm in males but as eggs in females?

  1. #1 X sex chromosome gametes: Why do they result as sperm in males but as eggs in females? 
    Forum Professor jrmonroe's Avatar
    Join Date
    Mar 2010
    Posts
    1,444
    Well, the title says it all.

    Consider the gametes with an X sex chromosome. Why does a male's body produce sperm for an X gamete, but a female's body produces an egg? The same question could be asked about why males always produce sperm, and females always produce eggs, but with the X sex chromosome gamete, the contents could theoretically be exactly the same in the male-produced gamete and in the female-produced gamete.

    So, why the different outcome? Why is their "cell fate" different?

    (Not homework, just curious.)


    Grief is the price we pay for love. (CM Parkes) Our postillion has been struck by lightning. (Unknown) War is always the choice of the chosen who will not have to fight. (Bono) The years tell much what the days never knew. (RW Emerson) Reality is not always probable, or likely. (JL Borges)
    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,222
    Omitting the which-came-first-chicken-or-the-egg, one reason might be simply be the size of the cells in question. An ovum is the largest cell in the human body. It's actually visible to the naked eye. They are much more biologically "expensive" to produce, a mere one or two per fertile cycle. Sperm are tiny by comparison and they're produced in their thousands every day*. They have much more scope for variation than ova do.

    *It's one of the reasons why researchers find it so much harder to produce an oral or injectable male contraceptive.


    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Mar 2014
    Posts
    65
    The sex of the adult determines whether sperm or eggs are produced.
    This is controlled by the Y chromosome in the XY sex-determination system.
    Females always produce eggs containing an X chromosome.
    Males always produce sperm (whether they contain X or Y chromosomes).

    In other sex-determination systems, the chromosome in the egg controls the resultant sex.
    Reply With Quote  
     

  5. #4  
    Forum Professor jrmonroe's Avatar
    Join Date
    Mar 2010
    Posts
    1,444
    So an egg is a huge metropolis-like gamete, and a sperm is a small gamete with a tail, all determined by the adult producing it, and it has nothing to do with the genetic content of the gamete itself?

    Grief is the price we pay for love. (CM Parkes) Our postillion has been struck by lightning. (Unknown) War is always the choice of the chosen who will not have to fight. (Bono) The years tell much what the days never knew. (RW Emerson) Reality is not always probable, or likely. (JL Borges)
    Reply With Quote  
     

  6. #5  
    Forum Professor Daecon's Avatar
    Join Date
    Jul 2013
    Location
    New Zealand
    Posts
    1,288
    Quote Originally Posted by jrmonroe View Post
    So an egg is a huge metropolis-like gamete, and a sperm is a small gamete with a tail, all determined by the adult producing it, and it has nothing to do with the genetic content of the gamete itself?
    Yes, I believe so. The gender of the adult determines the type of gamete produced. The chromosomes themselves are irrelevant. After all, each gamete has more than just one single chromosome in it.

    Unless nature is going to go for a million different varieties of gamete depending on the combination of chromosomes present within, it's a lot easier to determine it based on the gender of the adult producing the gametes.
    Reply With Quote  
     

  7. #6  
    Forum Professor jrmonroe's Avatar
    Join Date
    Mar 2010
    Posts
    1,444
    Okay, more along my question. Where in the sperm is the "software" that causes it to swim along toward the egg? Is there already DNA or RNA in the sperm to do that? Does the "software" run from the haploid genome that it carries? Or is the "software" separate from the haploid genome, which is merely along for the ride?
    Grief is the price we pay for love. (CM Parkes) Our postillion has been struck by lightning. (Unknown) War is always the choice of the chosen who will not have to fight. (Bono) The years tell much what the days never knew. (RW Emerson) Reality is not always probable, or likely. (JL Borges)
    Reply With Quote  
     

  8. #7  
    Forum Professor Zwirko's Avatar
    Join Date
    Sep 2008
    Location
    55 N, 3 W
    Posts
    1,085
    No "software". The genetic material in a sperm cell is inactive and tightly packaged. There are no ribosomes*, golgi, endoplasmic reticulum etc, so no protein synthesis is happening either. The energy of its swimming motion is provided by the densely packed mitochondria which power the large flagellum of the sperm cell. Sperm cells also have chemotactic abilities - they can change their behaviour in response to chemical stimuli. Eggs, for example, release chemicals that attract sperm cells.

    * Sperm cells contain many mRNAs some of which appear to be translated on mitochondrial ribosomes. I don't know what their function is.
    Reply With Quote  
     

  9. #8  
    Forum Professor Zwolver's Avatar
    Join Date
    May 2006
    Location
    Netherlands
    Posts
    1,667
    @zwirko, i didn't know a sperm cell had the ability to respond to chemical stimuli, other than normal cells do. Due to shear numbers of the sperm, do they really need to go to the egg. Isn't it good enough just to randomly disperse at a certain speed?

    @jrmonroe, whether it becomes an ovum, or a sperm cell all depends on the hormones the body is producing. Plus, before dividing, a sperm cell will have proteins created by the y chromosome, both in the x and the y sperm.
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
    Reply With Quote  
     

  10. #9  
    Forum Professor Zwirko's Avatar
    Join Date
    Sep 2008
    Location
    55 N, 3 W
    Posts
    1,085
    Yep, spermatocytes can do chemotaxis (as well as thermotaxis). I believe it's best studied in simple marine organisms though. In humans, progesterone is thought function as a chemoattractant for spermatocytes, which can be detected by spermatocytes at incredibly low concentrations. There are some other small molecules that may be involved as well.


    Here's a wiki article on "Sperm Guidance".
    Reply With Quote  
     

Similar Threads

  1. Replies: 9
    Last Post: July 21st, 2010, 11:34 AM
  2. HPV vaccination for males
    By i_feel_tiredsleepy in forum Health & Medicine
    Replies: 15
    Last Post: March 23rd, 2009, 05:01 PM
  3. Why do females when they...
    By Quantime in forum General Discussion
    Replies: 16
    Last Post: April 30th, 2008, 04:05 AM
  4. Why is there a preference by females of a male bum?
    By Quantime in forum Behavior and Psychology
    Replies: 28
    Last Post: January 23rd, 2008, 09:43 AM
  5. Are males superior to females?
    By in forum Biology
    Replies: 104
    Last Post: September 25th, 2006, 08:40 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •