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Sex linked inheritance pedigree 2016.ppt
- 2. Wait…. What????? • What’s a “mosaic”? • Remember the FLUID MOSAIC MODEL???? – The Plasma Membrane – P.S. What is a Plasma Membrane? • An individual (organism, artwork, organelle) made up of smaller, different ”pieces”… • So, in a way, WE ARE MOSAICS, too!
- 3. Calico Cats • Calico Cats can ONLY BE Female!
- 4. Why???? • Because a cat’s fur color is linked to two different alleles on the “X” chromosome • And…For a cat to have more than two colors… • It must have TWO X CHROMOSOMES!
- 5. Sex-Linked Inheritance • Sex-Linked Inheritance means that a gene (or multiple genes) are carried on one of the sex chromosomes
- 6. Sex-Linked Inheritance • Remember, Females have XX and Males are XY. – The Y has very few genes - mainly those that contribute to male characteristics. (Only about 87 genes total.) – The X much more genetic information – for gender and other characteristics. (About 2050 genes!)
- 7. Sex-Linked Inheritance • Some genes for a disorder/disease are located on one of the sex chromosomes • If the gene is linked to the “Y” chromosome, women will not have the disorder. – Why? _________________________________ • If the gene is linked to the “X” chromosome, and it is recessive, women will not express the disorder. – Why? ______________________________________ • If the gene on “X” is dominant… both will express it!
- 8. Who is usually affected by Sex-Linked Disorders? • MEN! Genes for certain traits are on the X chromosome only… – Since Men only have one X chromosome then they are more likely to have the disorder – Women are somewhat protected since they have two X chromosomes and are less likely to inherit receive disorders. • If women receive a recessive gene on one X chromosome, they are called “carriers” because they “carry” the gene but don’t express the disorder
- 9. Sex-Linked Disorders • Affected males never pass the disease to their sons – Men give their “Y” to their sons! • Affected males pass the defective X chromosome to all of their daughters, who are described as carriers – This means they carry the disease-causing allele but generally show no symptoms • Female carriers pass the defective X chromosome to… – half their sons (affected by the disease) – half their daughters (who are carriers) – The other children inherit the normal copy of the chromosome
- 10. How do you solve Sex-linked Problems? • You determine which trait (or disorder) is dominant or recessive • Set up a punnett square using XX for females and XY for males. – Assign alleles for X only! • Solve as usual, keeping in mind that the Y chromosome has no allele! Genotypes: XRXr , XRY Phenotypes: All offspring have red eyes. If Red eyes are dominant and sex-linked, show the cross between a homozygous red eyed female and a white eyed male.
- 11. Your Turn! • Hemophilia is a sex-linked trait where XH gives normal blood clotting and is dominant to the hemophilia allele Xh • Identify the genotypes of… 1) a woman with normal blood clotting whose father had hemophilia 2) a normal man whose father had hemophilia. • What is the probability that a mating between these two individuals will produce a child, regardless of sex, that has hemophilia?
- 12. Set up the Punnett Square! - a woman with normal blood clotting whose father had hemophilia XHXh - a normal man whose father had hemophilia XHY Genotypes: Phenotypes:
- 13. What are some X-linked disorders? • ALD • Hypertrichosis • Duchenne muscular dystrophy • Hunter Syndrome • Menkes disease(kinky hair syndrome) • Hemophilia • Color blindness • Inherited diabetes (Type 1)
- 14. ALD (Adrenoleukodystrophy) • A deadly genetic disease that is a result of fatty acid buildup caused by the enzymes not functioning properly • Causes damage to the nerves, resulting in neurological issues and, later, death
- 15. Hypertrichosis • An abnormal amount of hair growth over the body – Informally called werewolf syndrome, because the appearance is similar to the mythical werewolf
- 16. Hypertrichosis
- 18. Color Blindness • Having a decreased ability to see some colors or differences in colors • Red-Green is most common
- 19. Think how difficult some things would be if you have colorblindness
- 20. What about this…. Imagine life without being able to see true colors!
- 21. Menke’s Disease (Kinky Hair Syndrome) • Rapid deterioration of the nervous system. • Weak muscle tone, sagging facial features, seizures, developmental delay, and intellectual disability caused by enzymes not functioning • Children with Menkes syndrome typically begin to develop symptoms during infancy and often do not live past age 6
- 22. Menke’s Disease
- 23. Hemophilia • The “Royal Blood Disease” impairs the body's ability to make blood clots – Clots are needed to stop bleeding • This results in people bleeding longer after an injury and an increased risk of bleeding inside joints or the brain
- 24. Hemophilia • Remember the Royal Family?
- 25. Tay-Sachs • Tay-Sachs disease is a rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spine • Enzymes are the culprit AGAIN! • Paralysis of the nerves cause eventual death
- 27. Duchene Muscular Dystrophy • Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and weakness • Until relatively recently, boys with DMD usually did not survive much beyond their teen years – Advances in cardiac and respiratory care means that survival into the early 30s is becoming more common
- 29. PKU (PhenylKetonUrea) • Decreased metabolism of the amino acid phenylalanine – Enzymes can’t break it down! • Untreated PKU can lead to intellectual disability, seizures and death
- 30. PKU
- 31. Cystic Fibrosis (CF) • A genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine Cystic Fibrosis • The enzymes required to break down mucous are not functioning, so the mucous collects and clogs…
- 32. SCID (Severe combined immunodeficiency) • Do you know “David, the Boy in the Bubble”, who was born without a working immune system?
- 33. SCID • What happens when your immune system doesn’t work??? – https://www.nytimes.com/video/u s/100000004077071/the-boy-in- the-bubble.html
- 34. Albinism • Albinism is an inherited genetic condition that reduces the amount of melanin pigment formed in the skin, hair and/or eyes. Albinism occurs in all racial and ethnic groups throughout the world. – As well as other species!
- 35. Albino Animals
- 36. Different degrees of Albinism…
- 37. Y linked • Hairy ears