In the Wikipedia article for biological sex, I read the following sentence.

"The gametes produced by an organism are determined by its sex:..."

However, is it not through the gametes produced by an organism that "sex" is defined? Should this sentence be the other way around?

  • $\begingroup$ Please clarify, do you mean the type of gametes produced (i.e. eggs and sperm) are determined by the sex? $\endgroup$ – rg255 Nov 27 '15 at 7:12
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    $\begingroup$ related: What's the difference between male and female? $\endgroup$ – fileunderwater Nov 27 '15 at 8:25
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    $\begingroup$ Short version of the above link; sex is often determined by chomosomal makeup, but it can also be determined by other factors (e.g. environmental cues or sequential hermaphroditism). Sexes are defined in terms of Anisogamy (different-sized gametes). $\endgroup$ – fileunderwater Nov 27 '15 at 8:40

The gametes produced by an organism are determined by the organism's sex - Thus, that statement from Wikipedia appears correct to me. In the case of humans, males have two different sex chromosomes. Thus, males produce gametes with either a Y-chromosome or an X-chromosome (XY). Female humans also have two sex chromosomes, but they are two different X chromosomes (XX). Thus, when females produce gametes they have a single copy of one of the X chromosomes in each gamete. In most cases, a fertilized embryo results and is either XX or XY - in the case of males the embryo gets the Y from Dad and the other sex chromosome is one of the two X's from Mom. In the case of a female the embryo gets the X chromosome from Dad and one of the two X's from Mom.

Here is an image describing what I said above with a link to the page to read more:

enter image description here

Here is a link from a basic genetics course from Dr. Young in the UK that has a more in-depth explanation.

Here is a link to another article from Nature Education that help explain how this works in humans as well as some other organisms that are slightly different.


No. You are confused. There are different types of chromosomal sex determination. If one sex is heterogametic (an example of one system like this are mammals, which have an X and a Y chromosome) then the sexual phenotype (male versus female) is determined by the presence (or absence) of the Y chromosome. If you have a Y you will develop testes,and the androgens produced by the testes will direct all of your secondary sexual characteristics to develop the male fates.

In the absence of a Y chromosome the default developmental pathway of the somatic gonads is to form ovaries. The ovaries produce estrogen which will direct all of your secondary sexual characteristics to develop female fates.

Gametes are either sperm or eggs. Early after fertilization some of the embryonic cells get sequestered away to form the primordial germ cells (PGCs). Later on these cells will mature in the somatic gonad to form the germline, giving rise to more sperm (or eggs). These germline cells have no effect on the sex or gender of a mammal. In some animals (like model organisms that can be subjected to genetic screens) you can isolate sexually transformed mutants where, for example the XX animals develop as males and produce sperm, and the XY animals develop as females and produce oocytes. There are other possible mutant situations as well where the male sex produces oocytes, and the female sex produces sperm.

  • $\begingroup$ you're interpreting the question differently - the sex of the organism determines the gametes - males produce haploid sperm with either an X or Y sex chromosome, females produce ova that have one of two of the X chromosomes. I agree with you though - the way the sex is determined is not by the necessary presence of a particular chromosome though. $\endgroup$ – Vance L Albaugh Nov 27 '15 at 6:38
  • $\begingroup$ It looks like we need clarification from the person asking the question $\endgroup$ – Vance L Albaugh Nov 27 '15 at 6:46
  • $\begingroup$ In mammals carrying a strong loss-of-function mutation in the TDF (testis determining factor) gene, which is the only gene directly required for sex determination on the Y chromosome, both the XX and the XY individuals develop as fertile females. No TDF = no testes, no testes = no androgens, no androgens = default female developmental pathway. This shows that the Y is necessary for male fates. IF: you create an XX transgenic mouse carrying the TDF gene, THEN: it will develop as a fertile XX male. This shows that TDF (SRY or sry) is sufficient for male fates. $\endgroup$ – mdperry Nov 27 '15 at 11:42
  • $\begingroup$ I agree with you - though the most common condition is that the sex of the organism determines the gametes – you're talking about a very rare type of anomaly - how rare is a strong loss of function mutation in the TDF? $\endgroup$ – Vance L Albaugh Nov 27 '15 at 12:51
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    $\begingroup$ We may me be addressing different sections of the original poster's query. I do not object to the edited title. My comments are replying to the body of the question: ". . . is it not through the gametes produced by an organism that 'sex' is defined?" To this I posted an answer that starts "No. You are confused." My gametes in no way influence or affect my sex or gender. The primary signals for mammalian sex determination are, as far as I know, chromosomal. It is the zygotic chromosomes that dictate and control the development of the embryos somatic and germline sex. $\endgroup$ – mdperry Nov 28 '15 at 1:19

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