* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Sex-Linked Genes - Mr. Kleiman`s Wiki
Survey
Document related concepts
Causes of transsexuality wikipedia , lookup
Sexual dimorphism wikipedia , lookup
Gene expression programming wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Genome (book) wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Designer baby wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Genomic imprinting wikipedia , lookup
Microevolution wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Y chromosome wikipedia , lookup
Neocentromere wikipedia , lookup
Transcript
Sex-Linked Genes Below is a human karyotype. This is a picture of all of the chromosomes in one human cell. All cells in the body of one individual (except in the gametes) will have this same set of chromosomes. Unsorted Chromosomes Male Karyotype Sex Chromosomes: The X and the Y chromosomes are called sex chromosomes because they determine the gender of an individual In mammals, if you have two X chromosomes, you will be a female if you have one X and one Y chromosome you will be a male The X Chromosome is larger than the Y chromosome, therefore it codes for more traits. Sex Chromosomes do not only code for sexual characteristics! Let us create an irregular Punnett square using the entire sex chromosomes, rather than just one allele, to show the probability of offspring being male or female. P generation: Mother = XX Father = XY X Y X X XX XX XY XY “Genotype” = 2 XX : 50% 2 XY 50% Phenotype = 2 female : 2 male 50% 50% In reality the human world population is approximately 51% male and 49% female. Why are the X and Y chromosomes NOT considered to be homologous chromosomes even though they pair up and separate during meiosis? _____________________________________________________________________________________ _____________________________________________________________________________________ This means that alleles on the sex chromosomes are a special case for inheritance. We call genes on the X or Y chromosomes sex linked traits. Females have no chance of receiving Y-linked genes and males only receive ONE X chromosome This means that males only have one allele for all X-linked traits. They are more likely to show recessive X-linked traits because they cannot be masked by a dominant allele Sex Linked Diseases / Disorders Since the Y chromosome is small and doesn’t code for many traits, Y-linked diseases are rare Most sex-linked disorders (faulty genes on sex chromosomes) are X-linked. We need special Punnett squares to show the inheritance of X-linked Characteristics which show whole sex chromosomes Eg. Hemophilia – a rare recessive X-linked disease that prevents blood from clotting. What are the chances of offspring getting hemophilia if only the mother is a carrier of the hemophilia allele, but does not have hemophilia herself? Let A = allele for normal blood clotting a = allele for Hemophilia XA Xa XA XA XA XA Xa Y A a X Y X Y “Genotype” = Phenotype = P Generation: Mother = XAXa Female 1 XA XA : 1 XA Xa 25% 25% No Hemophilia : 75% Father = XAY Male 1 XA Y : 1 Xa Y 25% 25% Hemophilia 25% If Male : If Female: 50% chance 0% chance Why do males have more of a chance of having Hemophilia than females? _____________________________________________________________________________________ _____________________________________________________________________________________ On a separate page, answer the following question: In humans, colorblindness (b) is an example of a sex-linked recessive trait. If a colourblind male reproduces with a female who is not colourblind, but carries the colourblindness (b) allele, what are the chances that their children will be colourblind? Compare the chances if it is a son vs. a daughter. Sex-Linked Genes Below is a human ___________________. This is a picture of all of the chromosomes in one human cell. All cells in the body of one individual (except in the gametes) will have this same set of chromosomes. Unsorted Chromosomes Male Karyotype Sex Chromosomes: The X and the Y chromosomes are called sex chromosomes because they determine the ________________________ of an individual In mammals, if you have two X chromosomes, you will be a ___________________ if you have one X and one Y chromosome you will be a ___________________ The X Chromosome is ____________ than the Y chromosome, therefore it codes for more traits. Sex Chromosomes do not only code for sexual characteristics! Let us create an irregular Punnett square using the entire sex chromosomes, rather than just one allele, to show the probability of offspring being male or female. P generation: Mother = XX Father = XY X Y X X XX XX XY XY “Genotype” = 2 XX : 50% 2 XY 50% Phenotype = 2 female : 2 male 50% 50% In reality the human world population is approximately 51% male and 49% female. Why are the X and Y chromosomes NOT considered to be homologous chromosomes even though they pair up and separate during meiosis? _____________________________________________________________________________________ _____________________________________________________________________________________ This means that alleles on the sex chromosomes are a special case for inheritance. We call genes on the X or Y chromosomes ____________________________________________ Females have no chance of receiving Y-linked genes and males only receive ONE X chromosome This means that males only have one allele for all X-linked traits. They are more likely to show recessive X-linked traits because they cannot be masked by a dominant allele Sex Linked Diseases / Disorders Since the Y chromosome is small and doesn’t code for many traits, Y-linked diseases are rare Most sex-linked disorders (faulty genes on sex chromosomes) are X-linked. We need special Punnett squares to show the inheritance of X-linked Characteristics which show whole sex chromosomes Eg. Hemophilia – a rare recessive X-linked disease that prevents blood from clotting. What are the chances of offspring getting hemophilia if only the mother is a carrier of the hemophilia allele, but does not have hemophilia herself? Let A = allele for normal blood clotting a = allele for Hemophilia XA Xa XA XA XA XA Xa Y A a X Y X Y “Genotype” = Phenotype = P Generation: Mother = XAXa Female 1 XA XA : 1 XA Xa 25% 25% No Hemophilia : 75% Father = XAY Male 1 XA Y : 1 Xa Y 25% 25% Hemophilia 25% If Male : If Female: 50% chance 0% chance Why do males have more of a chance of having Hemophilia than females? _____________________________________________________________________________________ _____________________________________________________________________________________ On a separate page, answer the following question: In humans, colorblindness (b) is an example of a sex-linked recessive trait. If a colourblind male reproduces with a female who is not colourblind, but carries the colourblindness (b) allele, what are the chances that their children will be colourblind? Compare the chances if it is a son vs. a daughter.