logging in or signing up sex linked and pedigrees Flemel 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: 10977 Category: News & Reports.. License: All Rights Reserved Like it (7) Dislike it (0) Added: August 11, 2007 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... By: chbowden (39 month(s) ago) This is a great presentation. I'd like to download it. Saving..... Post Reply Close Saving..... Edit Comment Close By: heinri13 (39 month(s) ago) i would like to download a copy too. Saving..... Post Reply Close Saving..... Edit Comment Close By: nani_mbbs (47 month(s) ago) its good.i want to down load it Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Slide1: Sex-Linked Traits and Pedigrees Slide2: The Location of Genes Remember that genes for specific traits are coded for in our DNA -- our (humans) DNA is divided into 23 pairs of chromosomes -- all chromosome pairs are homologous (coding for the same traits, EXCEPT for the 23rd pair) The 23rd pair are known as sex chromosomes -- they determine whether an individual is male or female -- #23 chromosomes come in two varieties, X, and Y Slide3: X and Y Chromosomes If a human individual has two X chromosomes (XX), they are female, and both chromosomes are homologous If a human individual has one X and one Y chromosome, they are male, and the 23rd pair of chromosomes is NOT homologous -- in other organisms, XX individuals are male and XY individuals are female X and Y chromosomes differ in many ways Slide4: The X Chromosome The X chromosome contains genes for over 2300 traits -- most of these traits are not involved in determining sex Genes on the X chromosome are expressed in both males and females The X chromosome has a centromere in the middle and is fairly large in size Slide5: The Y Chromosome The Y chromosome is short and stubby and has a centromere near one end The Y chromosome contains only about 25 genes The most important gene on the Y chromosome is the sex-determining gene (SRY) -- if SRY is present, testes form and a male develops -- is SRY is absent, ovaries form and a female develops Slide6: How Sex is Determined We can treat the sex chromosomes just like alleles (remember alleles are on each chromosome in a homologous pair) The father has an X and a Y chromosome to give The mother has two X chromosomes. Therefore the cross looks like this: As you can see, the chance of each sex being born is 50% X Y X X XX XY XX XY Slide7: Traits on X and Y What about traits located on the X chromosome? Traits on the X chromosome behave in the normal dominant/recessive relationship for individuals with two X chromosomes (female), however, what about individuals who only have one X chromosome and one Y? -- remember Y chromosomes contain almost no genes For XY individuals (males), whatever trait is expressed on the X chromosome will be shown in the male individual -- we call traits on the X-chromosome sex-linked Slide8: The Bigger Problem Many unwanted traits are recessive traits located on the X chromosome. -- this is not a big deal for someone who has two X chromosomes (female), because the other chromosome could have the dominant allele -- if a male gets the recessive trait on his X chromosome, however, he gets the unwanted phenotype Traits that are passed this way: -- red/green colorblindness -- hemophilia -- baldness Slide9: Sex-Linked Crosses When we want to see how sex-linked traits are passed, we do a sex-linked crossed. We write alleles so that the chromosome X is shown with an upper or lower-case superscript for the trait (dominant or recessive), and Y has no superscript We also try to figure out if it is a boy or girl, what the percentage of each phenotype will be Females who are heterozygous for a recessive trait are called carriers Slide10: Practice Problem Hemophilia, a disease where blood does not clot properly, is caused by a recessive sex-linked allele. A female, who is a carrier for hemophilia and a normal male have a child. What is the probability that the child will be born with hemophilia? What is the probability that a female child will be born with hemophilia? What about a male child? Slide11: Tracing Inherited Traits Many times, individuals have questions about a specific trait or traits that run in families -- this could be a question as to whether or not future generations could get a gene for an undesirable trait, like a genetic disease -- this could also be a question as to whether a gene that codes for a specific trait is dominant, recessive, autosomal (on chromosomes 1 – 22), or sex-linked In order to trace the development of a trait through a population, and figure out the answer, we construct a chart known as a pedigree Slide12: Reading a Pedigree Pedigrees are read from top to bottom Each generation of a family is placed in its own row, with the older generations on top of younger generations Squares represent males Circles represent females If a male and female are connected by a square, they have mated and had offspring -- offspring are hung 'bracket-style' from the line connecting the two parents Individuals who are shaded-in are afflicted by the trait Individuals who are half-shaded are carriers (heterozygous) for the trait Slide13: Symbols in a Pedigree Slide14: Reading Pedigrees The hardest part of pedigrees is reading the pedigree and then trying to assess whether the trait was either: -- autosomal dominant -- autosomal recessive -- sex-linked dominant -- sex-linked recessive The best method to figure this out is to assign genotypes to affected individuals and then look at what the offspring of individuals should be if the cross follows each of the four patterns . . . Some examples. . . Slide15: Autosomal Recessive Pedigree Notice, in this pedigree how the only individual with the trait has parents who are BOTH carriers. Therefore, the trait is probably recessive. Also, since males can be carriers, the trait must be autsomal and not sex-linked Slide16: Autosomal Dominant Pedigree Notice how there are NO CARRIERS. All individuals with the allele show the phenotype. This is a pretty good clue that the trait is dominant. Since this trait is not always given by males to females, it is also probably autosomal Slide17: Sex-Linked Dominant Pedigree All females from the affected male have the trait, but not all males from affected females have the trait, this means it must be sex-linked and dominant. Also, there are no carriers Slide18: Sex-Linked Recessive Pedigree Notice how there are no male carriers. Additionally, the female carrier in generation 2 gave the trait to 50% of her male offspring and the affected male in generation 1 had 100% of his daughters as carriers. This is definitely sex-linked and recessive You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
sex linked and pedigrees Flemel 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: 10977 Category: News & Reports.. License: All Rights Reserved Like it (7) Dislike it (0) Added: August 11, 2007 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... By: chbowden (39 month(s) ago) This is a great presentation. I'd like to download it. Saving..... Post Reply Close Saving..... Edit Comment Close By: heinri13 (39 month(s) ago) i would like to download a copy too. Saving..... Post Reply Close Saving..... Edit Comment Close By: nani_mbbs (47 month(s) ago) its good.i want to down load it Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Slide1: Sex-Linked Traits and Pedigrees Slide2: The Location of Genes Remember that genes for specific traits are coded for in our DNA -- our (humans) DNA is divided into 23 pairs of chromosomes -- all chromosome pairs are homologous (coding for the same traits, EXCEPT for the 23rd pair) The 23rd pair are known as sex chromosomes -- they determine whether an individual is male or female -- #23 chromosomes come in two varieties, X, and Y Slide3: X and Y Chromosomes If a human individual has two X chromosomes (XX), they are female, and both chromosomes are homologous If a human individual has one X and one Y chromosome, they are male, and the 23rd pair of chromosomes is NOT homologous -- in other organisms, XX individuals are male and XY individuals are female X and Y chromosomes differ in many ways Slide4: The X Chromosome The X chromosome contains genes for over 2300 traits -- most of these traits are not involved in determining sex Genes on the X chromosome are expressed in both males and females The X chromosome has a centromere in the middle and is fairly large in size Slide5: The Y Chromosome The Y chromosome is short and stubby and has a centromere near one end The Y chromosome contains only about 25 genes The most important gene on the Y chromosome is the sex-determining gene (SRY) -- if SRY is present, testes form and a male develops -- is SRY is absent, ovaries form and a female develops Slide6: How Sex is Determined We can treat the sex chromosomes just like alleles (remember alleles are on each chromosome in a homologous pair) The father has an X and a Y chromosome to give The mother has two X chromosomes. Therefore the cross looks like this: As you can see, the chance of each sex being born is 50% X Y X X XX XY XX XY Slide7: Traits on X and Y What about traits located on the X chromosome? Traits on the X chromosome behave in the normal dominant/recessive relationship for individuals with two X chromosomes (female), however, what about individuals who only have one X chromosome and one Y? -- remember Y chromosomes contain almost no genes For XY individuals (males), whatever trait is expressed on the X chromosome will be shown in the male individual -- we call traits on the X-chromosome sex-linked Slide8: The Bigger Problem Many unwanted traits are recessive traits located on the X chromosome. -- this is not a big deal for someone who has two X chromosomes (female), because the other chromosome could have the dominant allele -- if a male gets the recessive trait on his X chromosome, however, he gets the unwanted phenotype Traits that are passed this way: -- red/green colorblindness -- hemophilia -- baldness Slide9: Sex-Linked Crosses When we want to see how sex-linked traits are passed, we do a sex-linked crossed. We write alleles so that the chromosome X is shown with an upper or lower-case superscript for the trait (dominant or recessive), and Y has no superscript We also try to figure out if it is a boy or girl, what the percentage of each phenotype will be Females who are heterozygous for a recessive trait are called carriers Slide10: Practice Problem Hemophilia, a disease where blood does not clot properly, is caused by a recessive sex-linked allele. A female, who is a carrier for hemophilia and a normal male have a child. What is the probability that the child will be born with hemophilia? What is the probability that a female child will be born with hemophilia? What about a male child? Slide11: Tracing Inherited Traits Many times, individuals have questions about a specific trait or traits that run in families -- this could be a question as to whether or not future generations could get a gene for an undesirable trait, like a genetic disease -- this could also be a question as to whether a gene that codes for a specific trait is dominant, recessive, autosomal (on chromosomes 1 – 22), or sex-linked In order to trace the development of a trait through a population, and figure out the answer, we construct a chart known as a pedigree Slide12: Reading a Pedigree Pedigrees are read from top to bottom Each generation of a family is placed in its own row, with the older generations on top of younger generations Squares represent males Circles represent females If a male and female are connected by a square, they have mated and had offspring -- offspring are hung 'bracket-style' from the line connecting the two parents Individuals who are shaded-in are afflicted by the trait Individuals who are half-shaded are carriers (heterozygous) for the trait Slide13: Symbols in a Pedigree Slide14: Reading Pedigrees The hardest part of pedigrees is reading the pedigree and then trying to assess whether the trait was either: -- autosomal dominant -- autosomal recessive -- sex-linked dominant -- sex-linked recessive The best method to figure this out is to assign genotypes to affected individuals and then look at what the offspring of individuals should be if the cross follows each of the four patterns . . . Some examples. . . Slide15: Autosomal Recessive Pedigree Notice, in this pedigree how the only individual with the trait has parents who are BOTH carriers. Therefore, the trait is probably recessive. Also, since males can be carriers, the trait must be autsomal and not sex-linked Slide16: Autosomal Dominant Pedigree Notice how there are NO CARRIERS. All individuals with the allele show the phenotype. This is a pretty good clue that the trait is dominant. Since this trait is not always given by males to females, it is also probably autosomal Slide17: Sex-Linked Dominant Pedigree All females from the affected male have the trait, but not all males from affected females have the trait, this means it must be sex-linked and dominant. Also, there are no carriers Slide18: Sex-Linked Recessive Pedigree Notice how there are no male carriers. Additionally, the female carrier in generation 2 gave the trait to 50% of her male offspring and the affected male in generation 1 had 100% of his daughters as carriers. This is definitely sex-linked and recessive