1. Genetic Disorders & Chromosomal Mutations
Chapter 12

2. Karyotype
Karyotype: picture of homologous chromosomes arranged in pairs
Human = 46 chromos. = 23 pairs
Sex chromosomes = determine sex of human (1 pair)
Male: XY
Female: XX
Autosomes = all others (22 pairs)

4. Pedigree Chart Shows relationships within a family
Each row is a different generation
Males: ■ Females: ●
Vertical: children; Horizontal: couples
Solid shape: has trait
Used to track appearance of traits
Can infer genotype of family members

5. Recessive Allele Disorders
Revealed only when dominant allele is absent
Disorders:
1) PKU (phenylketonuria): newborns lack enzyme to break down phenylaline in milk → severe mental retardation
2) Tay-Sachs: nervous system breakdown → death by age 4
Mostly central and eastern Europeans

6. Tay Sachs
PKU

7. Recessive Allele Disorders
3) Cystic Fibrosis: Causes respiratory and digestive problems
Most common fatal genetic disorder
4) Sickle Cell Disease: Results in bent and twisted red blood cells; ↓ blood O2 levels
Causes physical weakness; brain, heart, and spleen damage; death
Closely linked to malaria

8. Cystic Fibrosis
Sickle Cell Disease

9. Dominant Allele Disorders
Always revealed (even if recessive allele is present)
Disorders:
1) Acondroplasia: type of dwarfism
2) Huntington’s disease: progressive loss of muscle and mental functioning
No symptoms until in 30’s

10. Huntington’s
Disease
Acondroplasia

11. Mutations Mutation: any change in DNA
May involve entire chromosome or single nucleotide
May take place in ANY cell
May be beneficial or deadly (“lethal”)
Occur in 2 types of cells:
Germ-Cell Mutation: occur in gametes (sex cells); passed on to children
Somatic Mutation: occur in body cells

12. Chromosome Mutations
Non-Disjunction: failure of chromosomes to separate during meiosis
Results in gain/loss of entire chromosome
Trisomy 21: inheritance of extra chromos. #21
“Down Syndrome”

13. Karyotype of Trisomy 21

15. Chromosome Mutations
1) Deletion: loss of piece of chromosome

16. Chromosome Mutations
3) Translocation: swapping segments of non-homologous chromosomes