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Chromosomes are grouped as sex chromosomes or autosomes, with the X, Y, Z and W all falling in to the former category. The Z and X are present both in the homogametic and heterogametic sexes, and the Y and W only in the heterogametic sex.

Is there a collective name for the chromosomes in such groupings (X/Z & Y/W)?

I want to talk about Z- and X- (and analagous) chromosomes in general. Rather than having to write "The X-chromosome, and analagous chromosomes such as the Z-, are present in both sexes...." I'd like to say "The blank chromosomes are present in both sexes...."

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  • $\begingroup$ I can suggest one for Y/W- meiomorphic : Smaller in size. Heteromorphic is anyways used for dissimilar sex chromosomes. $\endgroup$ – WYSIWYG Sep 1 '14 at 11:19
  • $\begingroup$ I'm not aware of collective names but you could define one for the purpose of your paper. Inspired by @WYSIWYG you could try macro- and micro/meio- prefixes. I don't know if those terms would apply broadly to your needs. $\endgroup$ – Michael S Taylor Sep 1 '14 at 11:26
  • $\begingroup$ majo- prefix means greater.. But majomorphic sounds weird. Macro/micro also seem fine (but macro/micro are not comparative prefixes). You can actually ask this in a Greek/Latin forum :P $\endgroup$ – WYSIWYG Sep 1 '14 at 11:30
  • $\begingroup$ @WYSIWYG yes this is a good Greek and Latin question $\endgroup$ – user1357 Sep 2 '14 at 10:41
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I think you can safely use the terms heterogametic (Y/W) and homogametic (X/Z) chromosomes, meaning that a heterogametic chromosome is the chromosome which makes one of the sexes heterogametic (i.e. defines the difference between the two types of gametes of the respective sex).

These terms applied to chomosomes do have some usage in the literature, e.g. in this article.

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  • $\begingroup$ heterogametic/homogametic is used only in the diploid sense. What else could be an appropriate name for the gene-rich/deficient of the sex chromosomes? $\endgroup$ – WYSIWYG Sep 2 '14 at 4:20
  • $\begingroup$ @WYSIWYG: 1) How many cases of sex-chromosomal sex determination in haploid organisms are known? Or do you mean something else? 2) I don't know. By the way, the differences between the two (or three) sex chromosomes are not always pronounced to such a degree as observed in mammals. $\endgroup$ – har-wradim Sep 2 '14 at 11:01
  • $\begingroup$ you mistook me.. I meant it is said in reference to the genotype of the sex rather than the chromosome itself $\endgroup$ – WYSIWYG Sep 2 '14 at 11:04
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    $\begingroup$ @WYSIWYG My point was that the same terms can be also applied to chromosomes. E.g.: "... the heterogametic chromosome (Y or W) has repeatedly lost many genes ..." (p. 1646). $\endgroup$ – har-wradim Sep 2 '14 at 12:23
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I just tried a search of major and minor sex chromosomes and found a paper here by Judith Mank who refers to the X and Z as the Major Sex Chromosomes and Y and W as the Minor Sex Chromosomes.

I will therefore refer to the W and Y as minor sex chromosomes, and will use the term major sex chromosomes in reference to the X and Z. These terms are based on abundance and do not refer in any way to size (discussed below) or relative effect. In fact, the effect of the minor sex chromosomes is, in many ways, anything but minor.

I think I will go with this naming as the hetero-/homogametic chromosomes distinction could become confusing in the context I am using it (Talking about expression of the X/Z in the homogametic and heterogametic sex).

EDIT:

Further I think it is wrong because, while "heterogametic chromosome" would be somewhat suitable for Y/W chromosomes, to call the X and Z the homogametic chromosome is wrong because the X/Z can be present in both a homogametic sense (in females/males respectively) and a heterogametic sense (paired with a Y or W). Calling the X/Z the homogametic chromosome implies that it is only present in homogametic sexes no less than "minor sex chromosome" might imply a minor role for the Y.

Another suggestion could be to call the Y/W chromosomes the sex-limited chromosomes, but then the question of what to call the X/Z remains... non-limited? shared? sex-unlimited?

Or recombining and non-recombining sex chromosomes.

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    $\begingroup$ I'm not a fan of this usage since the mechanism of function varies so widely and the major/minor distinction implies something about the functional role of the two types. $\endgroup$ – Jack Aidley Sep 2 '14 at 8:55
  • $\begingroup$ @JackAidley that's why I put in the Mank clarification "the effect of the minor sex chromosomes is, in many ways, anything but minor." $\endgroup$ – rg255 Sep 2 '14 at 8:57
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    $\begingroup$ I agree with @JackAidley regarding meaning but at least you have precedence to cite and it appears to suit your needs. $\endgroup$ – Michael S Taylor Sep 2 '14 at 10:29
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    $\begingroup$ I am also not a fan but did not downvte $\endgroup$ – user1357 Sep 2 '14 at 10:42
  • $\begingroup$ @JackAidley Thanks for your input so far, please see the edits.. $\endgroup$ – rg255 Sep 2 '14 at 11:38
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Regarding the meio/majo or micro/macro suggestion, I do not think it is the way to go for the following reasons:

  • Micro and macro-chromosomes are terms already used in species such as chicken whose genomes combine very small and big chromosomes
  • Although this is more the exception than the rule, bear in mind that sometimes the Y chromosome is bigger than the X chromosome (e.g. in S. latifolia)

As for the initial question, I do not know of a term the X/Z - Y/W groups. What comes to my mind is the term sex-restricted sex chromosome for the Y/W (as it is normally present only in one sex) although it does not seem to be widely used according to Google.

You could also oppose them as recombining vs non recombining sex chromosome which would hold true for most heteromorphic sex chromosomes (if we do not take PAR into consideration). It might be confusing as some persons would think you speak about the pair and not the individual chromosome. However, it seems to be used in the literature.

I checked one of my manuscript on the topic and we used X/Z when needed.

Edit: first sentence clarified.

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  • $\begingroup$ instead of size sex chromosomes should be classified by their gene content. $\endgroup$ – WYSIWYG Sep 2 '14 at 4:22
  • $\begingroup$ I did not say we should classify by size (my second bullet point clearly shows this is not a general rule). Gene content of any of their property (e.g. recombination, segregation,...) is definitely a better way to go. $\endgroup$ – Philippe Sep 2 '14 at 11:39
  • $\begingroup$ Not you. I was saying in general (after considering your example) $\endgroup$ – WYSIWYG Sep 2 '14 at 11:48
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Based on answers and discussion so far and my own searches, I think there is no widely understood and used term for grouping the X/Z and W/Y chromosomes. You could coin your own term or pluck one from obscurity in the literature, however, I think you would probably be better off not doing so and simply writing X/Z and W/Y wherever you need to refer to the grouping.

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    $\begingroup$ I've mentally decided to start using WYsomes (pronounced why-somes) and ZXsomes (pronounced zicks-somes) for collective use. Of course, I'm not trying to publish a paper. :) $\endgroup$ – Michael S Taylor Sep 2 '14 at 16:32

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