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Mon Jan 7, 2019, 07:40 PM

Sex - It's really really complicated

Just when you begin to grok the X-Y chromosome sex determination, here come the birds.

Are the bird males XX, or XY?

Answer: Neither. They're ZZ, and the hens are ZW.

https://en.wikipedia.org/wiki/ZW_sex-determination_system

9 replies, 666 views

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Arrow 9 replies Author Time Post
Reply Sex - It's really really complicated (Original post)
Xipe Totec Jan 7 OP
dameatball Jan 7 #1
JDC Jan 7 #2
customerserviceguy Jan 7 #3
Xipe Totec Jan 7 #5
dameatball Jan 8 #7
Igel Jan 10 #8
Xipe Totec Jan 11 #9
Midnightwalk Jan 7 #4
Xipe Totec Jan 7 #6

Response to Xipe Totec (Original post)

Mon Jan 7, 2019, 08:01 PM

1. If I have never had sex with a bird, do I still need to read all this?

Thanksgiving not included of course.

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Response to dameatball (Reply #1)

Mon Jan 7, 2019, 08:10 PM

2. Good one

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Response to dameatball (Reply #1)

Mon Jan 7, 2019, 08:50 PM

3. It's not

all it's quacked up to be.

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Response to dameatball (Reply #1)

Mon Jan 7, 2019, 09:05 PM

5. Setting aside the funny reply, and it is funny.

Think about it this way:

Mammals and birds diverged before sexual differentiation was established. Then they developed sex through convergent evolution.

Sex is such an evolutionary advantageous strategy that it has evolved multiple times throughout life.

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Response to Xipe Totec (Reply #5)

Tue Jan 8, 2019, 04:26 AM

7. A platypus, a zebra finch and a komodo dragon walked into a bar.....:) Interesting post for sure.

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Response to Xipe Totec (Reply #5)

Thu Jan 10, 2019, 10:22 PM

8. Not sure that's entirely right.

Or, more accurately put, entirely necessary or observationally adequate.

It can be claimed that they they diverged before the two current systems were established.

Or maybe not.

https://en.wikipedia.org/wiki/Sex-determination_system#Evolution

Since argumentatio ex wiki seems in vogue.

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Response to Igel (Reply #8)

Fri Jan 11, 2019, 01:26 PM

9. As I said, it's really, really complicated. nt

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Response to Xipe Totec (Original post)

Mon Jan 7, 2019, 09:01 PM

4. Interesting topic

Thanks for posting this it gave me some interesting things to read about.

Learned there are 3 main systems, XY where the male has two different chromosomes and determine the sex of the offspring; X0 where the male gives an X or no chromosome; XW where the male is XX and the female determines sex by whether the egg has an X or W chromosome

Also read a little about X inactivation which prevents too much transcription of those genes in XY systems.

What surprised me most is it sounds like these systems exist in species that are unrelated. There are mammals with X0 systems and reptiles with XY. ZW systems exist in insects, reptiles and birds.

That sounds like these systems must have evolved multiple times? The wiki articles didnít talk about about that aspect, at least I didnít see it.

Sorry if I got any of this wrong. Interesting stuff.

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Response to Midnightwalk (Reply #4)

Mon Jan 7, 2019, 09:06 PM

6. You hit the nail in the head. See my reply above. nt

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