TPR Bio Review question Error?

[xylem29]

Wondering if anyone got this, on page 328, Ch.10, it asks a question about what would happen if an XY genotype lacked a testosterone receptor...

The answer says that testes are present (agree), external genitalia are female (disagree), and neither the mullerian or Wollfian ducts develop (agree).

My answer choice was D - testes and male external genitalia are present b/c I thought that if T was present, but no receptor, then cells just can't respond to it, thus internal male genitalia won't develop, but neither will female ones b/c MIF is present. However, T can still become DHT and thus, external male genitalia should still develop...right? Unless T and DHT use the same receptor?

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[estairella]

Wondering if anyone got this, on page 328, Ch.10, it asks a question about what would happen if an XY genotype lacked a testosterone receptor...

The answer says that testes are present (agree), external genitalia are female (disagree), and neither the mullerian or Wollfian ducts develop (agree).

My answer choice was D - testes and male external genitalia are present b/c I thought that if T was present, but no receptor, then cells just can't respond to it, thus internal male genitalia won't develop, but neither will female ones b/c MIF is present. However, T can still become DHT and thus, external male genitalia should still develop...right? Unless T and DHT use the same receptor?

I don't know what DHT is BUT, I can help you... one of my department professors specializes in sexual dysfunction.

Anyways, it sounds like a case of androgen insensitivity syndrome. The most important thing you have to remember is that default development is female. What I mean is, if you detesticularize or de-ovarize or whatever, any fetus (male or female), it will still develop external female genitalia.

If DHT is an androgen, then yes, it will bind to the same receptor. And in addition, unless I'm mistaken, genitalia development occurs when testosterone --(aromatized)--> estradiol in males (kinda counterintuitive, I know, but it's because testosterone can enter the brain and females with estradiol just have it circulating in blood).

I don't think any of that is REALLY important. Just remember that female is default.

 

[TMP-SMX]

Wondering if anyone got this, on page 328, Ch.10, it asks a question about what would happen if an XY genotype lacked a testosterone receptor...

The answer says that testes are present (agree), external genitalia are female (disagree), and neither the mullerian or Wollfian ducts develop (agree).

My answer choice was D - testes and male external genitalia are present b/c I thought that if T was present, but no receptor, then cells just can't respond to it, thus internal male genitalia won't develop, but neither will female ones b/c MIF is present. However, T can still become DHT and thus, external male genitalia should still develop...right? Unless T and DHT use the same receptor?

If the receptor is lacking the development of the male primary sexual characteristics will remain female. As was said, female is the default. And without testosterone the SRY gene on the Y chromosome can't do very much in terms of determining maleness. (The receptor is not present)

Ok that's enough. The previous poster told you enough.

 

[xylem29]

If the receptor is lacking the development of the male primary sexual characteristics will remain female. As was said, female is the default. And without testosterone the SRY gene on the Y chromosome can't do very much in terms of determining maleness. (The receptor is not present)

Ok that's enough. The previous poster told you enough.

DHT is dihydrotestosterone and it is required for scrotum and penis development. I thought about it and I don't think that T and DHT would have the same receptor b/c if the enzyme that converts T to DHT is missing, then you will get vagina and clitoris.

No, it won't remain female, the embryo still makes MIF which inhibits the mullerian duct. So there will be no internal genitalia, no uterus, fallopian tubes, but no vas deferens either...am i making sense? I thought that this is how it goes - SRY gene on Y determines the gonadal sex - you will get testes instead of the default ovaries. Then, the rest of sexual development depends completely on hormones or the lack of hormones (for females). No?

 

[estairella]

No, it won't remain female, the embryo still makes MIF which inhibits the mullerian duct. So there will be no internal genitalia, no uterus, fallopian tubes, but no vas deferens either...am i making sense? I thought that this is how it goes - SRY gene on Y determines the gonadal sex - you will get testes instead of the default ovaries. Then, the rest of sexual development depends completely on hormones or the lack of hormones (for females). No?

Your thinking is (partially) correct. There will be no internal female genitalia (except for undescended testes)... but... uhh, let's say hypothetically, there was nothing "externally" at all. Just smooth skin. How exactly does this poor man/woman pee? Externally, it will be female. The only difference is that the vagina will end prematurely and not lead to anything.

 

[photoelectric]

I don't know what DHT is BUT, I can help you... one of my department professors specializes in sexual dysfunction.

Anyways, it sounds like a case of androgen insensitivity syndrome. The most important thing you have to remember is that default development is female. What I mean is, if you detesticularize or de-ovarize or whatever, any fetus (male or female), it will still develop external female genitalia.

If DHT is an androgen, then yes, it will bind to the same receptor. And in addition, unless I'm mistaken, genitalia development occurs when testosterone --(aromatized)--> estradiol in males (kinda counterintuitive, I know, but it's because testosterone can enter the brain and females with estradiol just have it circulating in blood).

I don't think any of that is REALLY important. Just remember that female is default.

I think you're slightly off on the role of T > aromatized > E ...

-SRY on Y chrom = testes
-testes secrete T but no receptors = NO Wolffian ducts
-MIH = NO Mullerian ducts either, so NO internal genitalia
-female external genitalia by default (no T receptor, and MIH only inhibits internal development)
-T > aromatized > Estradiol = sets up the brain to be "male" (e.g. sexual responsivity etc.)
...keep in mind that other complications develop when puberty hits
disclaimer :: this is from behavioral neuroendocrinology that i took last semester

 

[xylem29]

I think you're slightly off on the role of T > aromatized > E ...

-SRY on Y chrom = testes
-testes secrete T but no receptors = NO Wolffian ducts
-MIH = NO Mullerian ducts either, so NO internal genitalia
-female external genitalia by default (no T receptor, and MIH only inhibits internal development)
-T > aromatized > Estradiol = sets up the brain to be "male" (e.g. sexual responsivity etc.)
...keep in mind that other complications develop when puberty hits
disclaimer :: this is from behavioral neuroendocrinology that i took last semester

So T also masculinizes the external tissues? And estradiol does not do that? Ok, now this makes more sense.

 

[mychelle774]

So T also masculinizes the external tissues? And estradiol does not do that? Ok, now this makes more sense.

Ooh rock on xylem! I remember this exact question from the homework, and I didn't really get TPR's explanation either. But I got it straightened out. I am so tempted to go back to my books and check if I still know what I'm talking about.

 

[xylem29]

Ooh rock on xylem! I remember this exact question from the homework, and I didn't really get TPR's explanation either. But I got it straightened out. I am so tempted to go back to my books and check if I still know what I'm talking about.

So what's the answer then?