1 / 12

Sex-Linked Inheritance

Sex-Linked Inheritance. Two copies of each autosomal gene affect phenotype. Mendel studied autosomal gene traits (these genes are on autosomes ), like hair texture. The “either-or” traits that were seen in your tutorial. Genes found on autosomes (1-22 for humans) = autosomal traits

zebulon
Download Presentation

Sex-Linked Inheritance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sex-Linked Inheritance

  2. Two copies of each autosomal gene affect phenotype • Mendel studied autosomal gene traits (these genes are on autosomes), like hair texture. • The “either-or” traits that were seen in your tutorial. • Genes found on autosomes (1-22 for humans) = autosomal traits • Genes found on sex chromosomes (pair 23 for humans) = sex-linked traits

  3. Sex determined by genes found on the X and Y chromosome Females: egg produced with an X chromosome X chromosome genes in mammals affect many traits. Males: ½ sperm cells contain X; and the other ½ contain Y Chromosome genes in mammals are responsible for male characteristics. Sex Determination X X X Y X X X X X Y X Y There is a 50/50 chance of child being a boy/girl

  4. Males & Females have Different Inheritance Patterns • ALL of a male’s sex-linked genes are expressed. • Males have no second copies of sex-linked genes. • Because of this, males can NEVERbe “carriers” of sex-linked traits or disorders. • Ex: Colorblindness, Hemophilia, Muscular dystrophy

  5. Defined: Inherited conditions found on X chromosome Usually recessive Females: XX chromosomes XH XH = healthy XH Xh = healthy carrier Xh Xh = disease Males: XY chromosomes XHY = healthy XhY = disease Rare in women (back-up X chromosome) Ex: Colorblindness, Hemophilia, Muscular dystrophy Sex-Linked Disorders

  6. Sample Colorblind Tests 4 Sex-Linked Traits:1. Normal Color Vision: A: 29,  B: 45,  C: --,  D: 26  2. Red-Green Color-Blind: A: 70,  B: --,  C: 5,  D: --  3. Red Color-blind: A: 70,  B: --,  C: 5,  D: 6  4. Green Color-Blind: A: 70,  B: --,  C: 5,  D: 2

  7. Let’s take a look at… Sex-Linked Punnett Squares

  8. What is the probability of getting: Daughter with hemophilia? 0% Carrier child? 25% Child with hemophilia? 25% Two healthy children? ¾ x ¾ = 9/16 (56%) Jen is a healthy carrier (XH Xh) of hemophilia and Adam has no history in his family (XH Y). Healthy girl Healthy boy Healthy girl (carrier) Disease boy

  9. What is the probability of getting a: Healthy son? 25% Healthy daughter? 25% Child with hemophilia? 50% Carrier child? 25% Kelly is a healthy carrier of hemophilia, but Jim suffers from the disease. Healthy girl (carrier) Healthy boy Disease girl Disease boy

  10. If the phenotype is more common in males, the gene is likely sex-linked.

  11. Let’s try a sex-linked problem: A man and a woman marry. The woman is a carrier of colorblindness, an X-linked disorder. They have 4 children, 3 boys and one girl. Two of the boys are colorblind, and the girl is a carrier. The carrier daughter marries a healthy man. a)What is the probability they will have a carrier? b)What is the probability they will have a child that is colorblind? XDXd XDY Xd Y Xd Y XDXd XDY XDY ? XD Xd XDXDXDXd XD Y 25% XD YXdY 25%

  12. REVIEW • How are sex-linked disorders different from autosome disorders? • Why are sex-linked disorders more common in males? • Write the genotype of a heterozygous dominant female. • Write the genotype of a carrier female. • Examine Kelly and Jim’s Punnett square. What are the chances they would have three children, all of whom are healthy?

More Related