Which chromosome is male

The X is labeled to the right of the top quadrant, while the minus sign is labeled outside the right quadrant. In this case, two of the four quadrants contain the genotype XX, resulting in female insects; the remaining two quadrants contain the genotype X-, resulting in male insects. Figure 7: A side-by-side comparison of sex determination systems in humans, insects, and birds. The diagram looks like a diamond that has been divided into four equal square cells.

The second Punnett square represents the sex determination system in insects. In this case, two of the four quadrants contain the genotype XX, resulting in female offspring; the remaining two quadrants contain the genotype X-, resulting in male offspring.

The third Punnett square represents the sex determination system in birds. In this case, two of the four quadrants contain the genotype ZZ, resulting in male offspring; the remaining two quadrants contain the genotype ZW, resulting in female offspring. More on sex determination. In some animals, sex can be determined by environmental conditions Sex Determination in Honeybees Scientists report sex reversal in a transgenic mous.

The variety of inheritance patterns described in this article illustrate that sex determination is a complex and varied feature among organisms. Key Questions How can environmental conditions determine sex in some animals?

What have honeybees taught scientists about sex determination? What do transgenic mice reveal about sex reversal? What did beetles and wasps teach us about sex chromosomes? Topic rooms within Genetics Close.

No topic rooms are there. Browse Visually. Other Topic Rooms Genetics. Student Voices. Creature Cast. Simply Science. In addition to these AZF loci, CNVs across the entire length of the Y chromosome have been investigated in male infertility [ , , , ].

To understand the association of gene CNVs and male infertility, 68 well-defined histopathologically confirmed cases of males with idiopathic testicular maturation arrest were analysed by SNP arrays [ ].

Men with normal spermatogenesis have not been investigated in this study; it is difficult to ascertain the significance of these CNVs. However, the discovery of PAR CNVs is biologically significant as X and Y chromosome pairing is made possible by the PARs and aberrations in chromosome structure at the PARs due to these CNVs would logically disrupt meiotic synapsis resulting in gametogenic failure and can be one of the aetiological factors underlying maturation arrest.

In addition, the PAR regions are rich in genes that escape X inactivation to maintain dosage compensation Fig. However, with the exception of genes in AZFc, no direct studies have been done comparing the CNVs with gene expression and spermatogenesis arrest.

Although there is universal agreement on the need for chromosome analysis by karyotyping in the workup of male infertility, there is still a lack of consensus regarding the clinical utility of testing for Y chromosome microdeletions in azoospermic and oligozoospermic males. While the American Society of Reproductive Medicine recommends the use of both, karyotyping and Y chromosome microdeletion studies, in males preparing to undergo Intracytoplasmic Sperm Injection [ICSI], the National Institute for Health and Care Excellence recommends only karyotyping for this group of patients [ 4 ].

In which patients molecular screening of the Y chromosome should be performed remains a dilemma. However there are population specific differences [ ] and in this scenario country specific guidelines are necessary. While analysis of Yq microdeletions is not indicated in patients with chromosomal abnormalities, obstructive azoospermia or hypogonadotropic hypogonadism, there are a number of examples of deletion carriers among non-idiopathic infertile men including Klinefelter syndrome and varicocele [ ].

Therefore, the presence of any diagnosis accompanied by azoo- or severe oligozoospermia should be an indication for AZF testing. We recommend Yq microdeletion testing in routine clinical practice for the following reasons. Identifying the cause of infertility: The Y chromosome contains several genes required for spermatogenesis and loss of one or more of such genes can cause impairment of this process.

By investigating the presence of Y chromosome microdeletions it is possible to determine the underlying genetic aetiology of male factor infertility and implement appropriate screening strategies for abnormal phenotypes.

Knowledge regarding these deletions will also help clinicians to provide more effective solutions to problems faced by infertile couples. For example, low sperm count and motility can be treated with hormones, anti-oxidants and lifestyle changes to improve the seminogram. However, these strategies of treatment will fail if the cause of infertility is genetic.

Also AZF screening is important before varicocoelectomy because deletion carriers will most likely not benefit from the surgical procedure.

Therefore, if the male partner is detected with a deletion the couple can directly be offered assisted reproductive techniques [ART] and not subjected to medical treatments to improve sperm count and motility. Predicting the prognosis of infertile males: While there exist numerous cases reports of AZFc deleted men can father a child, it is clinically observed that individuals harbouring Y chromosome microdeletions have progressive decline in sperm counts and can progress to azoospermia over time discussed above.

Thus males with mild or moderate oligozoospermia and Yq microdeletions would require a multiple followed-up for their possible progression to azoospermia. Thus the knowledge of the Yq status would aid in counselling these men and provide them an option of sperm cryopreservation for biological parenthood in future. Predicting outcome of testicular sperm aspiration [TESA]: Most males with Y chromosome microdeletions would be infertile and have absence of or very few sperms in ejaculate. To achieve pregnancy, sperm can be retrieved directly from the testes using techniques like testicular sperm extraction [TESE] or testicular sperm aspiration [TESA].

The occurrence and type of Yq microdeletion has been found to correlate with testicular phenotype and chance of sperm retrieval. Hence, screening for Y chromosome microdeletions can aid to predict the success of obtaining biological parenthood before undertaking invasive procedures.

Although yet controversial, Studies have reported slower fertilization rate, poor embryo quality, impaired blastocyst rate and lower overall success of ART in men with AZF deletions [ , , , ]. Hence, Yq microdeletion screening would also help in counselling couples regarding the probability of success rates after taking up ART to aid the couple in a rational decision making. Prevention of vertical transmission of the genetic defects: With the advent of ICSI, several live births are reported in couples where the male partner has a Yq microdeletion.

In some instances the partial AZFc deletion in the father has resulted in full deletion in the offspring [ ] which is a definite case of spermatogenic failure. Thus Y chromosome microdeletion testing is highly recommended for all infertile males who opt for ICSI so that the couple can make an informed choice of having biological parenthood at the risk of perpetuating infertility in the family. Risk of testicular cancers: The Y chromosome has long been a suspect candidate for gonadal cancers.

In individuals with gonadal dysgenesis that bear a full or even partial fragments of Y chromosome even in a few of the cells have a high risk of developing gonadal tumours specifically gonadoblastoma [ , , , ]. While these are limited observational studies, results of large case control studies are yet awaited. It is becoming increasingly apparent that beyond infertility, the knowledge of Yq microdeletions should also aid in predicting occurrence of cancers in men. Neuropsychiatric disorders and Yq microdeletions: While Yq microdeletions are strongly associated with infertility, reports are now emerging that atleast a subset of men with Y chromosome defects have higher prevalence of mental disorders.

Clinical histories also documented language delay, attention-deficit hyperactivity disorder ADHD and emotional and behavioural problems including anxiety and social disabilities in this cohort [ ].

However none of the infertile patients with non-terminal Yq microdeletions had any medical history of neuropsychiatric abnormalities [ ]. While further long term clinical follow-up data of men with Yq microdeletions is required; these preliminary observations do indicate the occurrence of other health risks beyond infertility in such men and this warrants testing of Y chromosome genetics in a clinical situation. Male infertility is a complex multifactorial condition that presents with highly heterogeneous phenotypes.

The Y chromosome plays a central role in regulation of spermatogenesis as it harbours Y-linked genes that are expressed in the testis and involved in various processes during spermatogenesis. The importance of these genes is evident from the observations that the removal of these genes causes distinct pathological testis phenotypes.

After 20 years from the first molecular definition of the AZF, Yq deletion screening has now become a routine test for infertile males in many countries to identify the cause of male infertility.

With clear-cut cause—effect relationship with severely impaired spermatogenesis, this test is now of help in even determining the success rates of sperm retrieval and prediction of success of assisted reproduction. Beyond these immediate applications, there are some clinically relevant issues associated with Yq deletions that need urgent attention. Presently, there is no long term follow-up data of men harbouring Yq microdeletions and there is an urgent need for data on the health status of children born from AZF deletion carriers.

It is especially relevant in two conditions 1 Increased risk of testicular cancers 2 Possible occurrence of neurological dysfunctions. However, little data exist on the incidence of testicular tumours in men with Yq microdeletions especially in second generation males born to fathers carrying the deletion.

Secondly, recent reports have demonstrated a significantly higher deletion load not only on the sex chromosome but also on autosomes of infertile men [ , ] indicate more widespread effects of such deletions on genomic stability. Coupled with the fact that many Y linked genes are also expressed in multiple tissues; how genomic instability and disturbances in gene expression owing to Yq deletions affect general physiological functions has not been investigated the long term implications of such effects are obscure.

With the recent data on higher prevalence of neurological problems in infertile men with Yq deletions it is imperative that we carry out detailed analysis of men with Yq deletions with an outlook beyond infertility. We hope that careful clinical observations coupled with detailed genetic information will provide important insights into these unanswered basic questions and give a different perspective to the field of androgenetics. Laboratory manual for the examination and processing of human semen.

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The sex-determining region of the human Y chromosome encodes a finger protein. ATM promotes the obligate XY crossover and both crossover control and chromosome axis integrity on autosomes.

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Recombination between palindromes P5 and P1 on the human Y chromosome causes massive deletions and spermatogenic failure. Zorrilla M, Yatsenko AN. The genetics of infertility: current status of the field.

This finding was further supported by another study that presented 0. The difference between the reported aneuploidy rate in X and Y chromosomes remains unclear even though aneuploidy was detected using similar methods i. Therefore, difference in the X and Y spermatozoa based on the frequency of aneuploidy in X and Y chromosomes remains unclear, which is in accordance with the other reported differences between these sperm types.

Recent studies have reported that exposure to certain EDs and pesticides induce sex chromosome abnormalities in spermatozoa Smith et al. Epidemiological study revealed a significant association between exposure to two organochlorine chemicals and sex chromosome disomy in the spermatozoa collected from men who underwent infertility assessment at the Massachusetts General Hospital between January and May Mcauliffe et al.

Moreover, similar epidemiological studies are warranted to identify the effects of various environmental chemicals and their association with chromosomal aberrations in the spermatozoa.

Genomics deals with the structure, function, evolution, and mapping of genomes Bader et al. A spermatozoon provides half of the nuclear genetic material to the diploid offspring via fertilization.

Thus, examination of the genes and protein content in spermatozoa might provide potential insights on their functions. It has been reported that haploid spermatids are capable of active chromosomal including sex chromosomes transcription important for their growth and survival Braun et al. As X and Y chromosome-bearing-spermatids express distinct genes encoded by each sex chromosome Hendriksen, , it might result in the proteomics difference between X and Y spermatozoa.

Although the majority of the genes are shared between X and Y spermatids via the intracellular bridge Braun et al. In this section, we review studies on the genomic and proteomic characteristics of X and Y spermatozoa and have elucidated their association with the morphophysiological characteristics of the two sperm types.

To date, very limited studies have identified and characterized genes that are differentially expressed in X and Y spermatozoa. Spermatozoa contain a minute amount of total RNA human spermatozoon, 0. This small amount of RNA per spermatozoon is the major drawback for research on gene expression in these cells. Chen et al. Using the RNA sequencing technology, it has been reported that the X chromosome encodes genes, whereas the Y chromosome encodes only 15 genes in mouse spermatozoa.

Some of these genes particularly receptors are also shown to be related to the growth, survivability, and functions of specific sperm types Umehara et al.

Therefore, differentially expressed genes might help in identifying the genetic background of stable differences between X and Y spermatozoa. When insemination was performed using Y spermatozoa, transcripts were downregulated and transcripts were upregulated in the oviduct.

Thus, the oviduct might have special biological sensors for screening spermatozoa. Bermejo-Alvarez et al. This indicates that the oocyte might also regulate an identical mechanism for reorganizing the different spermatozoa. Recent advances in genomic studies have provided several improved techniques that allow complete lysis of spermatozoa and isolation of total RNA Kirley, ; Meng and Feldman, ; Chen et al. Therefore, further studies are warranted to identify the genes expressed in the sexed spermatozoa of different species.

Mature spermatozoa undergo minimal transcription there are few ribosomes, so translation is not possible as well as protein synthesis Kwon et al. Therefore, these cells are extremely suitable for performing proteomic analysis. Direct comparison of protein levels in various cells can identify the markers responsible for differences between these cells Park et al.

Literature searches indicated that limited studies have been performed to evaluate the proteomic blueprint of X and Y spermatozoa to date. Hendriksen et al. This study indicated that sexing of spermatozoa cannot be performed based on their surface properties. This finding was partly supported by other investigators De Canio et al. In another recent study, Scott et al. Of these, the protein related to the embryo development EF-hand domain-containing protein 1 was expressed abundantly in the Y spermatozoa, whereas majority of other detected proteins were abundant in the X spermatozoa.

Since abundant proteins in Y spermatozoa help in post-fertilization embryo development and further in the survivability of male baby over female, which also support lightly higher males than female babies at birth.

In contrast, majority of these proteomics studies identified limited identical proteins despite the samples being collected from the same animal species bull. Moreover, Chen et al. In contrast, De Canio et al. Use of different proteomic approaches i. Based on these findings, it is essential to speculate that X and Y spermatozoa can at least be different based on their protein content; however, further studies are warranted to identify the validated markers that could differentiate these two cell types appropriately.

In addition, proteomic analysis of X and Y spermatozoa from different animal species should be conducted for their practical application particularly for immunosexing techniques. Proteins that are differentially expressed in X and Y spermatozoa are summarized in Table 4 data collected from published studies.

The differences in the protein content and associated signaling pathways between X and Y spermatozoa might provide a theoretical basis to distinguish between these sperm types. Nevertheless, it is uncertain whether these differences are correlated with the biological aspect of X and Y spermatozoa. By using the same program, we determined the associated disease processes that were regulated by the differentially expressed proteins in X and Y spermatozoa.

By using this simple illustration Figures 2 , 3 , one may have a hypothetical presumption regarding the occurrence of specific diseases in men and women. For example, L -lactate dehydrogenase A and testis-specific glyceraldehyde 3-phosphate dehydrogenase, which are highly expressed in X spermatozoa, are found to be functionally associated with breast neoplasm and cervical carcinoma Figure 2.

Both the cancers are the leading cause of cancer deaths in women Siegel et al. In accordance, epidemiological investigation in humans revealed relatively higher incidence of anemia Malhotra et al. These diseases were also found to be associated with proteins that were highly expressed in X spermatozoa Figure 2. Similarly, abundant proteins in Y spermatozoa, that is TUBA8 and GSTM3, were found to be associated with hepatic cancer and renal cancer, respectively, and the prevalence of both diseases were reported to be high in men compared to the women Woldrich et al.

However, few other diseases that are found to be related with the differentially expressed proteins either in the X and Y spermatozoa represent different results compared to the epidemiological data Figure 3. For example, heart failure was found to be related with CAPZB that was highly expressed in Y spermatozoa, however, its incidence is lower in men than that in women. Consistently, tuberculosis was found to be related with the altered functionality of TPI1 that was more highly expresses in X spermatozoa than in Y spermatozoa.

However, the incidence of this disease is high in men than women. These inconsistencies presumably due to the Pathway Studio program, generated protein pathways by using information present in the PubMed database, which are incapable to explain every disease condition precisely. In addition, despite the differential expression of a particular protein between two cell types, the existence of majority of the proteins is constant between them.

Therefore, the increased expression of a protein in the particular cell may not always represent their functional activation. Table 4. List of differentially expressed proteins in X and Y chromosome bearing spermatozoa.

Figure 2. Signaling pathways associated with highly differentiated proteins in X spermatozoa. Figure 3. Signaling pathways associated with highly differentiated proteins in Y spermatozoa. Nature has developed many mechanisms to make genetically different sperm phenotypically identical within a male to avoid a fertilization advantage of one allele over another.

An example very rare where different alleles affect fertility is the T allele system on Chromosome 17 in mice, in which great infertility occurs Colaco and Modi, Among the mechanisms employed by nature are intercellular bridges of clutches of 32 or more spermatagonia and spermatids so that RNA and proteins are exchanged in the clutches of the developing sperm with different genotypes, thus homogenizing the cytoplasm, cell membranes, and so on. The Sertoli nurse cells take over many essential cellular molecular functions during this period to compensate.

Additional mechanism is coating sperm with surface molecules during epididymal maturation to make sperm look alike.

These mechanisms explain why sperm are so identical, including X and Y sperm within a male. Indeed, differentiation between X and Y spermatozoa has been of immense interest to researchers, physicians, and breeders, since the beginning of recorded history.

Various methods have been used to distinguish between X and Y spermatozoa; however, the practical validity of these methods is questionable. The only consistent de novo difference identified between X and Y spermatozoon to date is in their DNA content, which might be responsible for the differential expression of some genes and proteins and the occurrence of certain diseases in a sex specific manner; however, it is unclear whether this difference in the DNA content results in other physical, chemical, and functional differences between X and Y spermatozoa.

Moreover, the ambiguity in the existing findings might be due to the use of non-specific or less-specific methods for distinguishing between X and Y spermatozoa. Therefore, further studies using more specific, non-invasive less injurious to cells methods to distinguish between the two sperm types for the sex preselection of offspring are warranted.

MR and M-GP conceived the idea. MR drafted the manuscript and prepared the artworks. M-GP supervised the whole work. Both authors crucially revised the manuscript for important intellectual content and approved the final version to be published. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. We thank the funding agencies for supporting our study.

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This XY sex-determination system is found in most mammals as well as some reptiles and plants. Whether a person has XX or XY chromosomes is determined when a sperm fertilizes an egg.

Unlike the body's other cells, the cells in the egg and sperm — called gametes or sex cells — possess only one chromosome. Gametes are produced by meiosis cell division, which results in the divided cells having half the number of chromosomes as the parent, or progenitor, cells.

In the case of humans, this means that parent cells have two chromosomes and gametes have one. All of the gametes in the mother's eggs possess X chromosomes. The father's sperm contains about half X and half Y chromosomes. The sperm are the variable factor in determining the sex of the baby. If the sperm carries an X chromosome, it will combine with the egg's X chromosome to form a female zygote.

If the sperm carries a Y chromosome , it will result in a male. During fertilization, gametes from the sperm combine with gametes from the egg to form a zygote.

The zygote contains two sets of 23 chromosomes, for the required There are some variations, though.