1. Genetic Disorders

2. Pedigree
Illustrates
inheritance

3. Pedigrees Cont.
Shaded circles or squares indicate trait being present
Empty circles and squares indicate the trait is not present
Each horizontal line of circles and squares is a generation
Generations are designated with a Roman numeral with most recent on bottom
A half shaded circle or square represents a carrier or a heterozygous individual
A horizontal line connecting a circle and a square indicate parents
Each Individual is iven a number

4. Analyzing a Pedigree F1= 5 males with 2 legs
2 females: 1 died and the other has 2 legs
F2= 5 males: 4 with 2 legs and 1 w/4
4 females: 2 w/ 2legs 1w/four 1 w/no legs

5. Simple Recessive Heredity
Most genetic disorders are caused by recessive alleles. Many of the alleles are rare but an be found in certain ethnic groups
Cystic fibrosis: 1 in 20 carry recessive allele. 1 in 2000 babies born to white Americans have this disorder. Defective protein results in the formation of thick mucus in lungs and digestive tract

6. Simple Recessive Heredity
Tay Sachs: Disease of the central nervous system
The allele is fairly common in the U.S. in the Ashkenazic Jew population(eastern Europe)

7. Simple Recessive Heredity
Phenylketonuria- PKU
Absence of the enzyme that converts phenylalamine to another amino acid tyrosine. Without this enzyme, phenylalamine builds up in the body and causes damage to the central nervous system
Allele common in people whose ancestors came from Sweden and Norway

8. Simple Dominant Heredity
Huntington’s disease- lethal genetic disease caused by a rare dominant allele
It results in the breakdown of certain parts of the brain
Onset is between 30 and 50, so affected individuals may have had children before knowing they have the disease

9. Complex Patterns of Heredity
Incomplete dominance
The phenotype of the heterozygous individual is intermediate between the two homozygote

10. Complex Patterns of Heredity
Codominance- causes the phenotypes of both homozygous parents to be found in the heterogeneous offspring

11. Sex Determination Females –XX Males – XY 1:1 ratio of males to females
50% chance

12. Sex Linked Inheritance
Traits that are controlled by genes located on the sex chromosomes
Color blindness
Hemophilia- a single recessive allele will cause it in males but a female needs 2 recessives to have disease
Duchenne Muscular Dystrophy

13. Polygenic Inheritance
Inheritance pattern of a trait that is controlled by 2 or more genes
Skin color- 3-6 genes controlled by amount of melanin
Eye color- melanin
Hair color
Height in humans
All traits are typically heterozygotes and intermediate in phenotype
Phenotypes show a continuous range of variability

14. Multiple Alleles Blood Group Has more than 2 alleles
ABO- called gene I
Ia, Ib and I
Universal donor: 0
Universal receiver: AB

15. Sex influenced traits Traits influenced by hormones
Male Pattern Baldness

16. Nondisjunction
Failure of a chromosome to separate from its homologue during meiosis
1 gamete receives an extra copy of a chromosome and the other has one less
It is not inherited but random mistakes

17. Nondisjunction Disorders
Trisomy
Egg may have 24 chromosomes
Sperm of = 47
Example: Down Syndrome
Extra Copy is on chromosome #21
Mild to severe mental retardation
Muscle weakness
Short
Characteristic facial features

18. Down Syndrome

19. Nondisjunction in Sex Chromosomes
1 egg has 22 chromosomes lacks a X sex chromosome
If a normal sperm fertilizes this egg the resulting human will have 45 chromosomes
This is called monosamy or Turner Syndrome
Female appearance
Do not mature sexually
infertile
Has one sex chromosome X

20. Nondisjunction of Sex Chromosomes
Klinefelter’s syndrome
Extra X (XXY) trisomy
47 chromosomes
Feminine characteristics
Infertile
Mental retardation

21. Nondisjuction of sex chromosomes
Aneuploidy(trisomy)
47 chromosomes
No major differences
Fertile
May be taller than average
May have learning difficulties

22. There is no such thing as a human with just a Y
X carries the information necessary for development and Y carries very little
There is some research that suggests that it plays a big role in male fertility: production of sperm
If there is no X, the organism will die