Cytogenetics chromosome mutations aberrations evolution
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Cytogenetics: Chromosome Mutations, Aberrations & Evolution. Chromosomes. Prokaryote Eukaryote. Eukaryotic chromosomes. Human karyotype. Why do we care?. Many diseases and birth defects are a direct result of missing, broken, or extra chromosomes. Down Syndrome Cri du chat Syndrome

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Chromosomes
Chromosomes

Prokaryote Eukaryote




Why do we care
Why do we care?

Many diseases and birth defects are a direct result of missing, broken, or extra chromosomes.

  • Down Syndrome

  • Cri du chat Syndrome

  • Patau Syndrome


Mutations at the level of the homologous pair
Mutations at the level of the homologous pair

  • EUPLOIDY: "true" ploidy, meaning two members of each homologous pair.

  • ANEUPLOIDY: "not true" ploidy, meaning more or fewer members than two of each homologous pair.

    • MONOSOMY - one homolog; partner is missing

    • TRISOMY - three homologs

    • NULLISOMY- one entire homologous pair is missing.




How does it happen nondisjunction
How does it happen? Nondisjunction

Each chrom.

has two

chromatids


Trisomy patau syndrome
Trisomy: Patau Syndrome

  • 1/20,000 births

  • severe mental retardation

  • heart and organ defects

  • polydactyly

  • death by the age of one year


Structural changes
Structural Changes

  • Deletions (deficiencies)

  • Duplications

  • Inversions

  • Translocations



How can chromosomes break
How can chromosomes break?

Ionizing radiation (production of free radicals, which act like little atomic "cannon balls", blasting through strands of DNA or c'somes.

Chemical insult.

Why do they rejoin?

Break points of chromosomes are highly reactive ("sticky"), whereas normal ends of c'somes are capped by telomeres, which do not readily bond to other molecules.


  • Breaks that occur ______ __________________ __________________ will affect both newly formed chromatids, & all daughter cells arising from them.

  • Breaks that occur ______ ____________________ ____________________ may affect only one chromatid. (Thereafter, only the progeny carrying the broken chromatid will be affected.)


Cri du chat syndrome

_________________ __________________ will affect both newly formed chromatids, & all daughter cells arising from them.

_________________

Mental retardation

Slow motor skill development

Low birth weight and slow growth

Small head (microcephaly)

Partial webbing of fingers or toes

Wide-set eyes (hypertelorism)

High-pitched cry

Cri-du-chat Syndrome


Structural changes1
Structural Changes __________________ will affect both newly formed chromatids, & all daughter cells arising from them.

  • Deletions (deficiencies)

  • Duplications

  • Inversions

  • Translocations


Duplication
Duplication __________________ will affect both newly formed chromatids, & all daughter cells arising from them.


Duplications
Duplications __________________ will affect both newly formed chromatids, & all daughter cells arising from them.


Bar eye caused by duplication
Bar eye: caused by duplication __________________ will affect both newly formed chromatids, & all daughter cells arising from them.


Duplications source of evolutionary novelty

______________ __________________ will affect both newly formed chromatids, & all daughter cells arising from them.

______________

______________

______________

Duplications: source of evolutionary novelty?

Duplication is a source of new genes over evolutionary time: e.g., gene families like globins and MHC genes


Structural changes2
Structural Changes __________________ will affect both newly formed chromatids, & all daughter cells arising from them.

  • Deletions (deficiencies)

  • Duplications

  • Inversions

  • Translocations


Inversions
Inversions __________________ will affect both newly formed chromatids, & all daughter cells arising from them.


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