Sex - Linked Genes and Nondisjunction Disorders

Human Chromosomes One Human Chromosome has 46 chromosomes

Karyotype A picture of all chromosomes from an individual’s cells.

Autosomal Chromosomes 44 out of the 46 chromosomes

Sex Chromosomes 2 of the 46 chromosomes (determines an individual's sex) XX XY Female Male

Sex - Linked Genes Definition: Genes found on the Sex Chromosomes

Sex - Linked Genetic Disorders Mostly found on the X chromosome Sex - Linked Genetic Disorders Colorblindness Hemophilia Duchenne Muscular Dystrophy

Colorblindness Characteristics: Unable to distinguish certain colors (most commonly red and green) Mostly occurs in males Treatment: none Life Expectancy: normal

Can You See the Number 12?

Can you see the number 7?

What Colorblind People See NormalColorblind

What Colorblind People See NormalColorblind

Hemophilia Characteristics: Protein necessary for normal blood clotting is missing Can bleed to death from minor cuts or can suffer internal bleeding from bumps or bruises Treatment: Injections of normal clotting proteins Medical Complications: Forming antibodies against normal clotting proteins Life Expectancy: Normal if they keep up with their injections

An individual with hemophilia after he banged his knee

Duchenne Muscular Dystrophy Cause: Absence of dystrophin a protein that helps keep muscle cells intact Characteristics: Primarily affects males around the age of 3 Progressive weakening and loss of skeletal and voluntary muscle Treatment: Physical and Occupational therapy for range of motion and adaptive equipment NO CURE Life Expectancy: 20s

Individual with Muscular Dystrophy

Down Syndrome “Trisomy 21” Cause: Three copies of chromosome 21 Characteristics: Low muscle tone Flat facial profile Upward slant to eyes Small ears Protruding tongue Mild to moderate intellectual impairment Treatment: Physical, occupational, speech therapy Medical Problems: Congenital heart defects Hearing loss Vision problems Life expectancy: Average age is in the mid 50s

Down Syndrome

Down Syndrome Clip P4t2jR1g

Nondisjunction Disorders Failure of chromosome pairs to separate properly during cell division Disorders: Klinefelter’s Syndrome Down Syndrome Edward’s Syndrome Turner Syndrome

Klinefelter Syndrome XXY Cause: Nondisjunction Characteristics: Only affects MALES Usually don’t develop facial, underarm or pubic hair, don’t develop sperm and develop more breast tissue than normal due to decreased amounts of testosterone Learning disabilities Treatment: Testosterone injections Life Expectancy: Normal life span

An Indivdual with Klinefelter’s Syndrome

Karyotype of Klinefelter’s Syndrome

Edward’s Syndrome “Trisomy 18” Cause: 3 copies of chromosome 18 due to translocation Characteristics: Clenched hands Rocker bottom feet Abnormally shaped head Small head and jaw Abnormalities of organs Treatment: Supportive care Life Expectancy: Majority only live to one month

Physical Deformities in Edward’s Syndrome Clenched FistRocker Foot

Turner Syndrome Cause: Have only one X chromosome or a one full X chromosome and one partial X chromosome Characteristics: Only affects girls Will not go through all the changes associated with puberty Infertile Webbed neck Low hair line at the back of the neck Average height 4’7’’ Treatment: Growth hormone Estrogen injections Life Expectancy: normal

Karotype of Turner Syndrome

Turner Syndrome (Webbed Neck and Low Hair Line)