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Very short answer No, not all males of all sexual species have Y chromosomes. You might want to have a look to the Wikipedia page on sex-determination systems. Long answer Diversity among the species that reproduce sexually Not all species that have sexual reproduction have sexes. Yeasts, for example, have mating types but no sex. Diversity among the ...


20

Actually, no. There are also recombination prone regions of the Y chromosome that recombine and exchange material with X chromosomes, and these are called pseudoautosomal regions (PARs). Y chromosomes can be used similarly to mitochondrial DNA to build up profiles of ancestry, but the sequences used for this purpose lie outside PARs, in the non-recombining ...


13

No. There are many sex-determination systems. Mammals and fruitflies use the XX/XY sex-determination system — except for the platypus, which has 10 sex chromosomes. ZW sex-determination system is used by birds and some reptiles. It's similar but with the male having two of the same chromosome (ZZ) and the female being the heterogametic sex (ZW). There's ...


9

The reason is that X-inactivation is not complete (Carrell & Willard, 2005; Ahn & Lee, 2008), and as many as 15-25% of X-linked genes escape silencing (Carrell & Willard, 2005; Cheng et al, 2005). This means that some genes on the Barr body are expressed in XX-females, although often at lower levels compared to the active X-chromosome, and this ...


8

Like the other answer already said: yes, all cells in the human body contain all 2x 23 chromosomes (with the exception of cells that loose all nuclear DNA during maturation, like red blood cells, or cell produces by meiosis, which contain only a single set of 1x 23 chromosomes). However, the more interesting part of your question remains to be answered: ...


6

Short answer Some genes on the X chromosome escape X-inactivation. Two copies of these genes are needed for normal development. These genes are also present on the Y chromosome. Hence, healthy males and females both have two copies of these genes. In Turner's, the SHOX gene seems to be one of the culprits, which is needed for normal skeletal development. ...


6

Pseudoautosomal region in mammals On sexual chromosomes, we have a so-called PseudoAutosomal Region (PAR). The PAR is the region which still recombine with the Y chromosome (in males only) and is though to be important to allow separation of chromosomes during meiosis. Pseudoautosomal region and dosage compensation Because the PAR is diploid in males too, ...


6

The discovery of genetic sex determination, and determination of sex via male gametes (in XY species, female in ZW), occurred over some time in the late 1800's and early 1900's. Advances were made with methods to stain chromosomes and, in 1891, Henking noted that wasps produced sperm with a varying number of chromosomes. However, he was unable to gather ...


6

After a lot of research, I've finally found an answer. In the case of humans, it is practically impossible. See this article from wikipedia: During gestation, the cells of the primordial gonad that lie along the urogenital ridge are in a bipotential state, meaning they possess the ability to become either male cells (Sertoli and Leydig cells) or female ...


5

Here is the list! There are about 900 protein coding genes and about 500 non-coding transcribed sequences. It is not going to be feasible to explain you the function of every single one of those genes. Your question is hence too broad. You will find here on wikipedia a small subset of those ~900 genes. If your question was Are all genes that are on the ...


4

@AliceD's answer is excellent, but I thought it would be helpful to include an additional perspective. The issue here isn't that monosomy X shouldn't be a problem because the majority of one X chromosome is inactivated. It is that monosomy X isn't as big a problem as any other monosomy because the majority of one X chromosome is inactivated. Monosomies ...


4

From a computer science perspective, there's nothing at all special about DNA. It's stored as a simple ASCII text file consisting of repetitions of 4-15 different letters. DNA, the molecule, is a long chain of nearly identical smaller molecules (nucleotides) joined together. The nucleotides differ only in which of four possible bases (A,C,T/U or G) they ...


4

Barr bodies (X-chromosome inactivation) don't form in the initial fertilized embryo — it's not that one X-chromosome is inactivated, and then that same inactivation is passed down to daughter cells. Rather, X-chromosome inactivation occurs on a cell-by-cell basis in differentiated cells. Note how the accepted answer to the question you linked mentions that ...


3

During metaphase, all chromosomes look like an X with the exception of the chromosome Y. See below Why Y then? Well, according to wikipedia, just because the letter Y follows the letter X in the alphabet. Note that many species don't have sexual chromosomes and note that in many species, the Y-looking chromosome is present in the female but not in the ...


3

Sex Chromosomes and Sex Determination by Ilona Miko The first inkling that sex chromosomes were unique from all other chromosomes came from experiments conducted by German biologist Hermann Henking in 1891… Henking saw that some wasp sperm cells had 12 chromosomes, while others had only 11. Moreover, while observing the stages of meiosis that formed these ...


2

It is not easy for an individual to figure out if it is haploid or diploid at a given sequence. To my knowledge, this is feasible only by searching for specific case of heterozygosity. The most famous case is mating types in yeasts. In yeasts, haploid cells have mating types. Individuals are either "a" or "$\alpha$". Individuals can only fuse with ...


2

There are mechanisms through which the X-chromosome that has been turned into a Barr-body can be re-activated. This happens during cloning, but is also seen in some cells that turn into cancer cells. This paper discusses a lot of intriguing lessons we've learned from transplanting nuclei from one cell to another in frogs and mice. Interestingly, though the ...


2

You can answer this question for yourself using the modMine data warehouse for modENCODE datasets. All you need is a list of female-specific genes (using your identifier of choice, although FlyBase FBGxxxxxxxx are the simplest). You can use their list tools to upload your own list of identifiers, and then there are a bunch of widgets that will tell you ...


2

All cells except mature rbcs contain genetic material. So every cell must contain 46 chromosome containing sex chromosome as well


1

The ratio you are referring to is indeed computed aggregating multiple observations and thus it is a "statistical average". Any individual (or couple, in this case) can have a specific ratio that differs from the average one. Many factors may affect sex ratio, among which sperm/egg viability, chromosomal aberrations, and hormones misbalance are the ones ...


1

Most often, it seems that Turner syndrome is due to fertilization by a sperm cell lacking a sex chromosome. I wouldn't describe such a cell as "empty": it still has the other 22 chromosomes, but in meiosis the sex chromosomes failed to segregate appropriately. Monroy et al 2002 note that of 10 people with complete monosomy X, 9 had their single chromosome ...


1

After fertilization the diploid cells divide by mitosis. Chromosomes don’t need to pair with their partner during the eukaryotic cell cycle. After S-phase each chromosome has been duplicated (so there are 46 + 46 = 92). The two daughter chromosomes resulting from semi-conservative DNA replication are held together at one point: their centromeres. In M-...


1

There is 'homology' at the pseudo-autosomal region, a recombining region of the X and Y chromosomes.


1

Can sexual selection operate in temperature dependent sex determining organisms? Yes! Crocodiles are indeed a good example as the sex in determined by the temperature (ref) and they have some traits evolving through sexual selection (ref). I think you went almost all the way to the answer in your thoughts. Let's categorize things a little bit and talk ...


1

I posted this on Reddit as well, so credit to km1116 for working this out. Here is his response which follows my original logic (though I'm not sure if he is right): female x male: w x se F1: wild-type females and white males F2: 1/4 white-eyed males, 3/16 wild-type males, 1/16 sepia males, 1/4 white-eyed females, 3/16 wild-type females, ...


1

Very interesting question! And I don't think either that the linked Wikipedia article answers the question. Unfortunately I do not know the answer for sure, but I might have some relevant information to add. So, from my studies I know that Barr-bodies are not totally inactive, they, in fact, do have some very limited transcriptional activity. It might be ...


1

Fry (2010) borrowed his variables from Kidwell et al. (1977). Kidwell defines the fitness of each genotype as, $w_{m1}$, $w_{f1}$ = male and female fitness of the A$_1$A$_1$ genotype. $w_{m2}$, $w_{f2}$ = male and female fitness of the A$_1$A$_2$ genotype. $w_{m3}$, $w_{f3}$ = male and female fitness of the A$_2$A$_2$ genotype. Kidwell then establishes ...


1

Lizards of the genus Uta are apparently male heterogametic (XY) (Pennock et al. 1969). The XY system seems to be the most common mode of sex determination in iguanid lizards (Kasahara et al. 1983). Kasahara, Y et al. 1983. Chromosome mechanisms of sex determination, G- and C-band patterns and nucleolus organizer regions in Tropidurus torquatus (Sauria, ...


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