logging in or signing up Ch4 Brainy007 Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT 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: 1017 Category: Entertainment License: All Rights Reserved Like it (2) Dislike it (0) Added: August 03, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: oni_pt (16 month(s) ago) I'm interested this presentation, it's very informative to us, I want to request this file. Thank you. Saving..... Post Reply Close Saving..... Edit Comment Close By: sbhu (17 month(s) ago) hi it is a good Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Chapter 4 Sex Determination and Sex-Linked Characteristics: Chapter 4 Sex Determination and Sex-Linked Characteristics Sex may be determined by various mechanisms; for example, sex is determined by: - X:A ratio in C. elegans and Drosophila) - presence or absence of a sex-determining gene on the Y chromosome in humans and other mammals Slide2: Ova Sperm The male is the heterogametic sex. The female is the homogametic sex. (This is not always the case). The X is a large chromosome. The Y is much smaller and has few genes on it. Sex Determination in Mammals Male Determination in Mammals: Male Determination in Mammals Testis determining factor (TDF) produced by the SRY (sex-determining region of the Y) gene located on the Y chromosome. Sex Determination General Rule in Mammals:: Sex Determination General Rule in Mammals: If a Y chromosome is present, it will be a male. If a Y chromosome is not present, it will be a female. Slide5: XX males are possible if the SRY gene has translocated onto an autosome (TDF present). XY females are possible if the SRY gene is missing off of the Y and not present on an autosome (TDF lacking). Both of these are infertile. Sex is determined by presence or absence of TDF, not the Y chromosome, per se. Slide6: PAR = pseudoautosomal regions are the regions of homology on the X and Y and are essential for pairing in meiosis. Klinefelter Syndrome (XXY): Klinefelter Syndrome (XXY) (Sterile) Males With Multiple X Chromosomes: Males With Multiple X Chromosomes 48, XXXY 48, XXYY 49, XXXXY 49, XXXYY All are similar to XXY Klinefelter syndrome, but usually with more severe effects. 47, XYY: 47, XYY No distinguishing morphology (not a syndrome) Tall (2/3 are andgt; 6 feet tall) Slightly reduced average intelligence Increased risk of behavioral problems Turner Syndrome (XO): Turner Syndrome (XO) Females With Multiple X Chromosomes: Females With Multiple X Chromosomes 47, XXX – Mostly normal females. 48, XXXX 49, XXXXX These tend to have underdeveloped secondary sex characteristics, sterility and mental retardation. Dosage Compensation: Dosage Compensation Females have two copies of every X-linked gene; males have only one. How is this difference in gene dosage compensated for? Mammals: X-chromosome inactivation in females X-Chromosome Inactivation: X-Chromosome Inactivation Barr Bodies: Barr Bodies Barr bodies represent the inactive X chromosome and are normally found only in female somatic cells. Multiple X Chromosomes: Multiple X Chromosomes In cells with more than two X chromosomes, only one X remains genetically active and all the others become inactivated. Therefore: a woman with the chromosome constitution 47, XXX should have 2 Barr bodies in each cell. Slide16: Female MammalsAre Mosaic: Female Mammals Are Mosaic X-linked coat color gene CB = black, CY = yellow Males: XCBY black or XCYY yellow Females: XCBXCB black or XCYXCY yellow or XCBXCY calico or tortoiseshell Calico Cat: Calico Cat Slide19: Why doesn’t a female who is heterozygous for hemophilia A have hemophilia in half of her cells? Answer: She does, but the half of her cells that make clotting factor produce enough for the blood to clot normally. Question: Mechanism of X-chromosome Inactivation: Mechanism of X-chromosome Inactivation A region of the p arm of the X chromosome near the centromere called the X-inactivation center (XIC) is the control unit. This region contains the gene for X-inactive specific transcript (XIST). This RNA presumably coats the X chromosome that expresses it and then DNA methylation locks the chromosome in the inactive state. Slide21: If one of the two X chromosomes is inactivated in females, Why are XY females sterile? Why is XO not a normal female? Questions to contemplate: Sex Determination in Drosophila: Sex Determination in Drosophila Sex is determined by a 'tug-of-war' between female-determining genes on the X chromosome and male-determining genes on the autosomes. How is this different from sex determination in humans? Sex Determination in Drosophila: Sex Determination in Drosophila One complete set of autosomes is symbolized as 'A'. A normal female fly has two X chromosomes and two complete sets of autosomes (XXAA). In a female fly, the X:A ratio is 1:1. Sex Determination in Drosophila: Sex Determination in Drosophila A normal male fly has one X chromosome and two complete sets of autosomes (XYAA). In a male fly, the X:A ratio is 1/2. Drosophila: Intersex Drosophila 1/2 Male 1 Female 3/2 Female 2/3 What sex would these be in humans? Slide26: Sex-Linked Inheritance: Sex-Linked Inheritance Genes located on one sex chromosome, but not the other, exhibit sex-linked inheritance. Sex-Linked Inheritance: Sex-Linked Inheritance A father transmits his X chromosome to his daughters. XX × XY XX XY Sex-Linked Inheritance: Sex-Linked Inheritance A father transmits his Y chromosome to his sons. XX × XY XX XY X Linkage: X Linkage The X chromosome in mammals is large and contains lots of genes that have nothing to do with sex determination. A female has two X chromosomes and can be homozygous or heterozygous for X-linked genes. A male has a single X chromosome and is hemizygous for all X-linked genes. First Example of X-linked InheritanceT.H. Morgan - White-eye in Drosophila: First Example of X-linked Inheritance T.H. Morgan - White-eye in Drosophila Slide32: P1 red-eyed female × white-eyed male F1 all have red eyes F2 ¾ have red eyes ¼ have white eyes But, all the white-eyed flies were males! The gene for eye color is on the X chromosome: The gene for eye color is on the X chromosome Xw+ Xw+ XwY red white F1 x F1 cross: F1 x F1 cross F2 Slide35: Slide36: When reciprocal crosses give different results, the gene is probably sex-linked. X-linked Inheritance in Humans: X-linked Inheritance in Humans If a female expresses an X-linked recessive trait, her father also expressed it (and her mother is a carrier). A male cannot inherit an X-linked trait from his father. X-linked recessive traits show a 'criss-cross' pattern of expression in pedigrees. Slide38: Color 'Blindness' X-linked recessive red/green color confusion Slide39: Note: Males are much more likely than females to exhibit X-linked recessive traits. Slide40: Sex-limited traits are inherited autosomally, but require specific hormones for expression. They are normally only expressed in either males or females. The genes for secondary sexual characters (e.g. breasts, beards) are sex-limited. Sex-influenced traits are also inherited autosomally, but expressed more strongly in one sex than the other (e.g. pattern baldness is dominant in males, recessive in females). Sex-Limited and Sex-Influenced Traits You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
Ch4 Brainy007 Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT 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: 1017 Category: Entertainment License: All Rights Reserved Like it (2) Dislike it (0) Added: August 03, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: oni_pt (16 month(s) ago) I'm interested this presentation, it's very informative to us, I want to request this file. Thank you. Saving..... Post Reply Close Saving..... Edit Comment Close By: sbhu (17 month(s) ago) hi it is a good Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Chapter 4 Sex Determination and Sex-Linked Characteristics: Chapter 4 Sex Determination and Sex-Linked Characteristics Sex may be determined by various mechanisms; for example, sex is determined by: - X:A ratio in C. elegans and Drosophila) - presence or absence of a sex-determining gene on the Y chromosome in humans and other mammals Slide2: Ova Sperm The male is the heterogametic sex. The female is the homogametic sex. (This is not always the case). The X is a large chromosome. The Y is much smaller and has few genes on it. Sex Determination in Mammals Male Determination in Mammals: Male Determination in Mammals Testis determining factor (TDF) produced by the SRY (sex-determining region of the Y) gene located on the Y chromosome. Sex Determination General Rule in Mammals:: Sex Determination General Rule in Mammals: If a Y chromosome is present, it will be a male. If a Y chromosome is not present, it will be a female. Slide5: XX males are possible if the SRY gene has translocated onto an autosome (TDF present). XY females are possible if the SRY gene is missing off of the Y and not present on an autosome (TDF lacking). Both of these are infertile. Sex is determined by presence or absence of TDF, not the Y chromosome, per se. Slide6: PAR = pseudoautosomal regions are the regions of homology on the X and Y and are essential for pairing in meiosis. Klinefelter Syndrome (XXY): Klinefelter Syndrome (XXY) (Sterile) Males With Multiple X Chromosomes: Males With Multiple X Chromosomes 48, XXXY 48, XXYY 49, XXXXY 49, XXXYY All are similar to XXY Klinefelter syndrome, but usually with more severe effects. 47, XYY: 47, XYY No distinguishing morphology (not a syndrome) Tall (2/3 are andgt; 6 feet tall) Slightly reduced average intelligence Increased risk of behavioral problems Turner Syndrome (XO): Turner Syndrome (XO) Females With Multiple X Chromosomes: Females With Multiple X Chromosomes 47, XXX – Mostly normal females. 48, XXXX 49, XXXXX These tend to have underdeveloped secondary sex characteristics, sterility and mental retardation. Dosage Compensation: Dosage Compensation Females have two copies of every X-linked gene; males have only one. How is this difference in gene dosage compensated for? Mammals: X-chromosome inactivation in females X-Chromosome Inactivation: X-Chromosome Inactivation Barr Bodies: Barr Bodies Barr bodies represent the inactive X chromosome and are normally found only in female somatic cells. Multiple X Chromosomes: Multiple X Chromosomes In cells with more than two X chromosomes, only one X remains genetically active and all the others become inactivated. Therefore: a woman with the chromosome constitution 47, XXX should have 2 Barr bodies in each cell. Slide16: Female MammalsAre Mosaic: Female Mammals Are Mosaic X-linked coat color gene CB = black, CY = yellow Males: XCBY black or XCYY yellow Females: XCBXCB black or XCYXCY yellow or XCBXCY calico or tortoiseshell Calico Cat: Calico Cat Slide19: Why doesn’t a female who is heterozygous for hemophilia A have hemophilia in half of her cells? Answer: She does, but the half of her cells that make clotting factor produce enough for the blood to clot normally. Question: Mechanism of X-chromosome Inactivation: Mechanism of X-chromosome Inactivation A region of the p arm of the X chromosome near the centromere called the X-inactivation center (XIC) is the control unit. This region contains the gene for X-inactive specific transcript (XIST). This RNA presumably coats the X chromosome that expresses it and then DNA methylation locks the chromosome in the inactive state. Slide21: If one of the two X chromosomes is inactivated in females, Why are XY females sterile? Why is XO not a normal female? Questions to contemplate: Sex Determination in Drosophila: Sex Determination in Drosophila Sex is determined by a 'tug-of-war' between female-determining genes on the X chromosome and male-determining genes on the autosomes. How is this different from sex determination in humans? Sex Determination in Drosophila: Sex Determination in Drosophila One complete set of autosomes is symbolized as 'A'. A normal female fly has two X chromosomes and two complete sets of autosomes (XXAA). In a female fly, the X:A ratio is 1:1. Sex Determination in Drosophila: Sex Determination in Drosophila A normal male fly has one X chromosome and two complete sets of autosomes (XYAA). In a male fly, the X:A ratio is 1/2. Drosophila: Intersex Drosophila 1/2 Male 1 Female 3/2 Female 2/3 What sex would these be in humans? Slide26: Sex-Linked Inheritance: Sex-Linked Inheritance Genes located on one sex chromosome, but not the other, exhibit sex-linked inheritance. Sex-Linked Inheritance: Sex-Linked Inheritance A father transmits his X chromosome to his daughters. XX × XY XX XY Sex-Linked Inheritance: Sex-Linked Inheritance A father transmits his Y chromosome to his sons. XX × XY XX XY X Linkage: X Linkage The X chromosome in mammals is large and contains lots of genes that have nothing to do with sex determination. A female has two X chromosomes and can be homozygous or heterozygous for X-linked genes. A male has a single X chromosome and is hemizygous for all X-linked genes. First Example of X-linked InheritanceT.H. Morgan - White-eye in Drosophila: First Example of X-linked Inheritance T.H. Morgan - White-eye in Drosophila Slide32: P1 red-eyed female × white-eyed male F1 all have red eyes F2 ¾ have red eyes ¼ have white eyes But, all the white-eyed flies were males! The gene for eye color is on the X chromosome: The gene for eye color is on the X chromosome Xw+ Xw+ XwY red white F1 x F1 cross: F1 x F1 cross F2 Slide35: Slide36: When reciprocal crosses give different results, the gene is probably sex-linked. X-linked Inheritance in Humans: X-linked Inheritance in Humans If a female expresses an X-linked recessive trait, her father also expressed it (and her mother is a carrier). A male cannot inherit an X-linked trait from his father. X-linked recessive traits show a 'criss-cross' pattern of expression in pedigrees. Slide38: Color 'Blindness' X-linked recessive red/green color confusion Slide39: Note: Males are much more likely than females to exhibit X-linked recessive traits. Slide40: Sex-limited traits are inherited autosomally, but require specific hormones for expression. They are normally only expressed in either males or females. The genes for secondary sexual characters (e.g. breasts, beards) are sex-limited. Sex-influenced traits are also inherited autosomally, but expressed more strongly in one sex than the other (e.g. pattern baldness is dominant in males, recessive in females). Sex-Limited and Sex-Influenced Traits