Sex determined by genes found on the X and Y chromosome Females egg produced with an X chromosome Males ½ sperm cells contain X and the other ½ contain Y There is a ID: 919138
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Slide1
Sex-Linked
Inheritance
Slide2Sex Determination
Sex determined by
genes
found on the X and Y chromosomeFemales: egg produced with an X chromosomeMales: ½ sperm cells contain X; and the other ½ contain YThere is a 50/50 chance of child being a boy/girl
X X
X
Y
X
X
X
X
X
X
Y
Y
Slide3Sex-Linked Disorders
Defined
:
Inherited conditions found on X chromosomeUsually recessiveFemales: XX chromosomes XH XH = healthy
XH Xh
= healthy carrier Xh
Xh = diseaseMales: XY chromosomes XH
Y = healthy XhY = disease
Rare in women (back-up X chromosome)Ex: Colorblindness, Hemophilia
, Muscular dystrophy
Slide4Sample Colorblind Tests
Slide54 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
Sample Colorblind Tests
Slide61 min: Discuss with your neighbor.
Jen is a healthy carrier (X
H
Xh) of hemophilia and Adam has no history in his family (XH Y).What is the probability of:a. Daughter with hemophilia? 0%b. Carrier child? 25%c. Child with hemophilia? 25%d. All healthy children? 75%
Healthy girl
Healthy boy
Healthy girl (carrier)
Hemophiliac boy
¾
¾
Slide7Kelly does not have hemophilia even though her mother did. Jim (Kelly’s husband) is a hemophiliac. Their first child Barry is healthy but their other child Rachel is a hemophiliac. Draw a Pedigree for this family and a Punnett square for Jim and Kelly.
What is the probability of getting a:
a. Healthy son?
50%b. Healthy daughter? 50%c. Child with hemophilia? 50%d. Carrier child? 25%
Healthy girl (carrier)
Healthy boy
Hemophiliac girl
Hemophiliac boy
Kelly
Kelly’s
mother
Rachel
Jim
Barry
Slide8Review
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?