genetic disorders & chromosomal mutations chapter 12

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Genetic Disorders & Chromosomal Mutations Chapter 12

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Page 1: Genetic Disorders & Chromosomal Mutations Chapter 12

Genetic Disorders & Chromosomal Mutations

Chapter 12

Page 2: Genetic Disorders & Chromosomal Mutations Chapter 12

Karyotype

Karyotype: picture of homologous chromosomes arranged in pairsHuman = 46 chromos. = 23 pairs

Sex chromosomes = determine sex of human (1 pair)

• Male: XY • Female: XX

Autosomes = all others (22 pairs)

Page 3: Genetic Disorders & Chromosomal Mutations Chapter 12
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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

Page 5: Genetic Disorders & Chromosomal Mutations Chapter 12

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

Page 6: Genetic Disorders & Chromosomal Mutations Chapter 12

PKUTay Sachs

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Recessive Allele Disorders

3) Cystic Fibrosis: Causes respiratory and digestive problemsMost common fatal genetic disorder

4) Sickle Cell Disease: Results in bent and twisted red blood cells; ↓ blood O2 levelsCauses physical weakness; brain, heart, and

spleen damage; deathClosely linked to malaria

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Cystic Fibrosis Sickle Cell Disease

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Dominant Allele Disorders

Always revealed (even if recessive allele is present)

Disorders:1) Acondroplasia: type of dwarfism2) Huntington’s disease: progressive

loss of muscle and mental functioning• No symptoms until in 30’s

Page 10: Genetic Disorders & Chromosomal Mutations Chapter 12

Acondro

plasi

a

Huntington’sDisease

Page 11: Genetic Disorders & Chromosomal Mutations Chapter 12

Mutations

Mutation: any change in DNAMay involve entire chromosome or

single nucleotideMay take place in ANY cellMay 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

Page 12: Genetic Disorders & Chromosomal Mutations Chapter 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”

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Karyotype of Trisomy 21

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Chromosome Mutations 1) Deletion: loss of piece of chromosome

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Chromosome Mutations 3) Translocation: swapping segments of non-

homologous chromosomes