logging in or signing up human sex determination rkpillai Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1031 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: October 01, 2010 This Presentation is Public Favorites: 0 Presentation Description The genetical basis of human sex determination Comments Posting comment... By: coolkingvaibhav (16 month(s) ago) i want to download a ppt on sex determination please allow me Saving..... Post Reply Close Saving..... Edit Comment Close By: coolkingvaibhav (16 month(s) ago) nc Saving..... Post Reply Close Saving..... Edit Comment Close By: moomelon (19 month(s) ago) that is really good Saving..... Post Reply Close By: rkpillai (19 month(s) ago) Thank you Saving..... Edit Comment Close Premium member Presentation Transcript Human Sex Determination : Human Sex Determination Dr. R.K. Pillai Dept of Zoology Hindu College MORADABAD – 244 001 Sex Determination in Man : Sex Determination in Man Sex determination in man is related to the X-Y chromosome make up. Autosomes play no part in determining the sex. The Y-chromosome determines the maleness A single Y can outweigh upto 5 Xs. The X-chromosome determines femaleness in the absence of any Ys. Human Karyotype : Human Karyotype X- Chromosome : X- Chromosome The human X chromosome is a medium-length, submetacentric chromosome. X- chromosome is intermediate in length between autosome pairs 7 and 8. In mitotic metaphase the X chromosome measures approximately 4.5 to 5.5 mm Y- Chromosome : Y- Chromosome The human Y-chromosome is small acrocentric chromosome. Y is intermediate in length between autosome pairs 20 and 21. Y chromosome is variable in length among different men. In most human males averages roughly 1.1mm in length. Unlike autosomes 21 and 22, the Y has no satellites. With fluorescent banding techniques, the longer arm fluoresces brilliantly in good quality preparations. Human Sex Determination : Human Sex Determination The female individuals are homogametic with chromosome constitution 44A+XX. Male individuals are heterogametic with chromosome constitution 44+XY. Females produce only one type of ova, all containing 22 autosomes and one X-chromosome. Males produce two types of spermatozoa, 50% with X-chromosome and 50% with Y-chromosome. Sex is determined at the time of fertilization by the nature of the sperm that fertilizes the egg. Y-bearing sperms produce male zygotes. X-bearing sperms produce female zygotes. Slide 7: X-carrying and Y-carrying sperms are produced in 1:1 ratio. The average ratio of women and men in human population is 1:1. Humans, like other mammals have a sex-determination mechanism that depends on Y chromosome (dominant Y system). Individuals with a Y chromosome (XY and XXY) develop as males. Individuals without a Y chromosome (XO, XX and XXX) develop as females. Unlike Drosophila X : autosome (A) ratio does not influence sex determination. Picture slide : Picture slide Bullet 1 Bullet 1 Slide 10: The key to sex determination in humans is the SRY (for Sex Region on the Y) gene located on the Y chromosome. SRY direct the medulla of bipotential gonads to develop into testes Testes produce male hormones( testosterone), initiates development of male sexual characteristics. In individuals without a functional SRY, the cortex of bipotential gonads to develop into ovaries. The ovaries produce female hormones (estrogens) that initiates the development of female sexual characteristics. Slide 11: Recent research has shown the presence of testis-determining factor (TDF) on the human Y chromosome. This factor corresponds to a gene called SRY (for sex-determining region Y). SRY is located just outside the pseudoautosomal region in the Y chromosome’s short arm. The discovery of SRY was made possible by the identification of unusual individuals with constitution XX males and XY females. Some of the XX males were found to carry a small piece of the Y- chromosome inserted into one of the X-chromosomes. This piece carried a gene responsible for maleness. Some of the XY females were found to carry an incomplete Y chromosome. A particular segment of chromosome with TDF was needed for male development. SRY gene is also present on the Y chromosome of mouse. Slide 13: After the formation of testes, testosterone secretion initiates the development of male sexual characteristics. Testosterone binds to receptors on many kinds of cells. Once bound, the hormone-receptor complex transmits signals to differentiate and develop distinct male characteristics such as heavy musculature, beard and deep voice. If testosterone signalling system fails, these characteristics do not appear and theindividual develops as a female. The normal male possesses a wild type Tfm (testicular feminization) gene on the short arm of X which produce testosterone receptor. The male with the tfm mutation does not produce testosterone receptor resulting in a syndrome called testicular feminization. The person with syndrome acquire female sexual characters, but does not possess ovaries and hence sterile. The tfm mutation is transmitted from mothers to sons (who are phenotypically female) in a typical X-linked pattern. X and Y Chromatin in Interphase Nuclei : X and Y Chromatin in Interphase Nuclei The sex chromosomal complement of an individual can be obtained by examining squamous epithelial cells from scrapping of the oral mucosa. When stained, most somatic cells of normal females show a characteristic structure, the Barr body. Normal males whose cells do not contain a Barr body, are sex chromatin negative. Because of various cytological factors, frequency of sex chromatin positive cells on scrapping of oral mucosa from females have been reported to range from 36 to 80% of cells examined. Slide 15: The Barr body is a small structure, about 1 mm in dimension, hemispherical, disc shaped, rod shaped or triangular in outline. Barr body lies attached to the inner surface of the nuclear membrane or in nerve cells, may be associated with nucleolus. In diploid cells of females the number of x chromosomes is one more than the number of the Barr bodies. Staining of XY (or XYY) cells with such fluorescent dyes as quinacrine hydrochloride discloses the brightly fluorescing Y chromosome. It is found in both mitotic metaphase as well as interphase nucleus. SEX DIFFERENTIATION : SEX DIFFERENTIATION Human sex can be classified into following five types: Genetic Sex Gonadal Sex Genital Sex Somatic Sex Sociopsychological Sex Genetic Sex : Genetic Sex Normal females ordinarily have two X chromosomes, normal males have one X and one Y. The genes on these chromosomes determine femaleness or maleness. So females have the genetic sex designation XX and males have the genetic sex designation XY. Gonadal Sex : Gonadal Sex Chemical substances (inductors) produced by embryonic XX cells act on the medullary regions of undifferentiated gonads to bring about development of the ovarian tissue. In XY embryos, however, inductors stimulate production of testes from the cortex of the undifferentiated gonads. Hence the XX genetic sex is ordinarily associated with ovarian gonadal sex and XY with testicular gonadal sex. Genital Sex : Genital Sex The embryonic gonads produce hormones that determine the morphology of the external genitalia and genital ducts. XX embryos normally develop ovaries, female external genitalia and Mullerian ducts. XY embryos, on the other hand ordinarily develop testis, male external genitalia and Wolffian ducts. In XY embryos the Mullerian ducts remain undeveloped. Thus there is a distinction between male and female genital sex. Somatic Sex : Somatic Sex Production of gonadal hormones continues to increase until at puberty, secondary sex characters appear. These include amount and distribution of hair, (e.g. facial, body, axillary and pubic), pelvic dimensions, general body proportions, subcutaneous fat over hips and thighs and breast development in the female as well as increased larynx size and deepening of the voice in the male. Sociopsychological Sex : Sociopsychological Sex In most individuals genetic sex, gonadal sex, genital sex and somatic sex are consistent. XX persons for example develop ovaries, female genitalia and female secondary sex characters. Ordinarily these persons are raised as females and adopt the feminine gender. A similar consistency from genital sex to sociopsychological sex is seen for XY individuals. You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
human sex determination rkpillai Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1031 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: October 01, 2010 This Presentation is Public Favorites: 0 Presentation Description The genetical basis of human sex determination Comments Posting comment... By: coolkingvaibhav (16 month(s) ago) i want to download a ppt on sex determination please allow me Saving..... Post Reply Close Saving..... Edit Comment Close By: coolkingvaibhav (16 month(s) ago) nc Saving..... Post Reply Close Saving..... Edit Comment Close By: moomelon (19 month(s) ago) that is really good Saving..... Post Reply Close By: rkpillai (19 month(s) ago) Thank you Saving..... Edit Comment Close Premium member Presentation Transcript Human Sex Determination : Human Sex Determination Dr. R.K. Pillai Dept of Zoology Hindu College MORADABAD – 244 001 Sex Determination in Man : Sex Determination in Man Sex determination in man is related to the X-Y chromosome make up. Autosomes play no part in determining the sex. The Y-chromosome determines the maleness A single Y can outweigh upto 5 Xs. The X-chromosome determines femaleness in the absence of any Ys. Human Karyotype : Human Karyotype X- Chromosome : X- Chromosome The human X chromosome is a medium-length, submetacentric chromosome. X- chromosome is intermediate in length between autosome pairs 7 and 8. In mitotic metaphase the X chromosome measures approximately 4.5 to 5.5 mm Y- Chromosome : Y- Chromosome The human Y-chromosome is small acrocentric chromosome. Y is intermediate in length between autosome pairs 20 and 21. Y chromosome is variable in length among different men. In most human males averages roughly 1.1mm in length. Unlike autosomes 21 and 22, the Y has no satellites. With fluorescent banding techniques, the longer arm fluoresces brilliantly in good quality preparations. Human Sex Determination : Human Sex Determination The female individuals are homogametic with chromosome constitution 44A+XX. Male individuals are heterogametic with chromosome constitution 44+XY. Females produce only one type of ova, all containing 22 autosomes and one X-chromosome. Males produce two types of spermatozoa, 50% with X-chromosome and 50% with Y-chromosome. Sex is determined at the time of fertilization by the nature of the sperm that fertilizes the egg. Y-bearing sperms produce male zygotes. X-bearing sperms produce female zygotes. Slide 7: X-carrying and Y-carrying sperms are produced in 1:1 ratio. The average ratio of women and men in human population is 1:1. Humans, like other mammals have a sex-determination mechanism that depends on Y chromosome (dominant Y system). Individuals with a Y chromosome (XY and XXY) develop as males. Individuals without a Y chromosome (XO, XX and XXX) develop as females. Unlike Drosophila X : autosome (A) ratio does not influence sex determination. Picture slide : Picture slide Bullet 1 Bullet 1 Slide 10: The key to sex determination in humans is the SRY (for Sex Region on the Y) gene located on the Y chromosome. SRY direct the medulla of bipotential gonads to develop into testes Testes produce male hormones( testosterone), initiates development of male sexual characteristics. In individuals without a functional SRY, the cortex of bipotential gonads to develop into ovaries. The ovaries produce female hormones (estrogens) that initiates the development of female sexual characteristics. Slide 11: Recent research has shown the presence of testis-determining factor (TDF) on the human Y chromosome. This factor corresponds to a gene called SRY (for sex-determining region Y). SRY is located just outside the pseudoautosomal region in the Y chromosome’s short arm. The discovery of SRY was made possible by the identification of unusual individuals with constitution XX males and XY females. Some of the XX males were found to carry a small piece of the Y- chromosome inserted into one of the X-chromosomes. This piece carried a gene responsible for maleness. Some of the XY females were found to carry an incomplete Y chromosome. A particular segment of chromosome with TDF was needed for male development. SRY gene is also present on the Y chromosome of mouse. Slide 13: After the formation of testes, testosterone secretion initiates the development of male sexual characteristics. Testosterone binds to receptors on many kinds of cells. Once bound, the hormone-receptor complex transmits signals to differentiate and develop distinct male characteristics such as heavy musculature, beard and deep voice. If testosterone signalling system fails, these characteristics do not appear and theindividual develops as a female. The normal male possesses a wild type Tfm (testicular feminization) gene on the short arm of X which produce testosterone receptor. The male with the tfm mutation does not produce testosterone receptor resulting in a syndrome called testicular feminization. The person with syndrome acquire female sexual characters, but does not possess ovaries and hence sterile. The tfm mutation is transmitted from mothers to sons (who are phenotypically female) in a typical X-linked pattern. X and Y Chromatin in Interphase Nuclei : X and Y Chromatin in Interphase Nuclei The sex chromosomal complement of an individual can be obtained by examining squamous epithelial cells from scrapping of the oral mucosa. When stained, most somatic cells of normal females show a characteristic structure, the Barr body. Normal males whose cells do not contain a Barr body, are sex chromatin negative. Because of various cytological factors, frequency of sex chromatin positive cells on scrapping of oral mucosa from females have been reported to range from 36 to 80% of cells examined. Slide 15: The Barr body is a small structure, about 1 mm in dimension, hemispherical, disc shaped, rod shaped or triangular in outline. Barr body lies attached to the inner surface of the nuclear membrane or in nerve cells, may be associated with nucleolus. In diploid cells of females the number of x chromosomes is one more than the number of the Barr bodies. Staining of XY (or XYY) cells with such fluorescent dyes as quinacrine hydrochloride discloses the brightly fluorescing Y chromosome. It is found in both mitotic metaphase as well as interphase nucleus. SEX DIFFERENTIATION : SEX DIFFERENTIATION Human sex can be classified into following five types: Genetic Sex Gonadal Sex Genital Sex Somatic Sex Sociopsychological Sex Genetic Sex : Genetic Sex Normal females ordinarily have two X chromosomes, normal males have one X and one Y. The genes on these chromosomes determine femaleness or maleness. So females have the genetic sex designation XX and males have the genetic sex designation XY. Gonadal Sex : Gonadal Sex Chemical substances (inductors) produced by embryonic XX cells act on the medullary regions of undifferentiated gonads to bring about development of the ovarian tissue. In XY embryos, however, inductors stimulate production of testes from the cortex of the undifferentiated gonads. Hence the XX genetic sex is ordinarily associated with ovarian gonadal sex and XY with testicular gonadal sex. Genital Sex : Genital Sex The embryonic gonads produce hormones that determine the morphology of the external genitalia and genital ducts. XX embryos normally develop ovaries, female external genitalia and Mullerian ducts. XY embryos, on the other hand ordinarily develop testis, male external genitalia and Wolffian ducts. In XY embryos the Mullerian ducts remain undeveloped. Thus there is a distinction between male and female genital sex. Somatic Sex : Somatic Sex Production of gonadal hormones continues to increase until at puberty, secondary sex characters appear. These include amount and distribution of hair, (e.g. facial, body, axillary and pubic), pelvic dimensions, general body proportions, subcutaneous fat over hips and thighs and breast development in the female as well as increased larynx size and deepening of the voice in the male. Sociopsychological Sex : Sociopsychological Sex In most individuals genetic sex, gonadal sex, genital sex and somatic sex are consistent. XX persons for example develop ovaries, female genitalia and female secondary sex characters. Ordinarily these persons are raised as females and adopt the feminine gender. A similar consistency from genital sex to sociopsychological sex is seen for XY individuals.