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Mutations

Mutations. A Few Words on Mutations. Mutations can be neutral, positive, damaging or lethal Can occur at the single base or chromosomal level Naturally occurring mutations are RANDOM can introduce new traits most mutations are harmful. Causes of Mutations. • radiation • chemical

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Mutations

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  1. Mutations

  2. A Few Words on Mutations • Mutations can be neutral, positive, damaging or lethal • Can occur at the single base or chromosomal level • Naturally occurring mutations are RANDOM • can introduce new traits • most mutations are harmful

  3. Causes of Mutations • radiation • chemical • high temperature • age

  4. Chromosomal Mutations • Structural • Change in length or arrangement of nucleotides on chromosomes • Nondisjunction • Change in chromosome number • Caused by errors in meiosis

  5. Structural Chromosomal Mutations • Cause birth defects or cancer • Can be one of the following: • Deletions • Duplications • Inversions • Translocations

  6. Deletion • When part of a chromosome is deleted, usually due to unequal crossing over.

  7. Cri-Du-Chat Syndrome • 1 in 216,000 births • 46 chromosomes • #5 Deletion of lower arm Symptoms: Moon-shaped face Heart disease Mentally retarded Malformed larynx Normal lifespan

  8. Duplication • When part of a chromosome is duplicated, again usually due to unequal crossing over.

  9. Huntington’s incidence: 1/10,000 in U.S. nervous system degenerates late onset may not show symptoms until past reproductive age Duplication

  10. Inversion • An inversion is a type of mutation where a sequence of nucleotides in the DNA is reversed, or inverted

  11. Translocation • Mutuation when a there is a rearrangement of parts between nonhomologouschromosomes

  12. Burkitt Lymphoma • Translocation of the Myc gene on chromosome 8 • Normal Myc genes control cell growth and division • Translocated Myc genes don’t function properly • Leads to cancer of the lymph nodes

  13. Nondisjuction • Error in meiosis in which chromosomes fail to separate. • Can happen in Meiosis I or Meiosis II

  14. Changes to Chromosome Number • Monosomy 2n-1 • 45 chromosomes • Turners (XO) • Trisomy 2n+1 • 47 chromosomes • Down syndrome(trisomy 21), Klinefelters (XXY), Triple X (XXX), Jacobs (XYY) • Polyploidy (Triploid, Tetraploid, etc)

  15. Down Syndrome: Trisomy Down Syndrome 1 in 31,000 births46 chromosomes XY=97% XX=3% #14/21 Translocation 1 in 1,250 births 47 chromosomesXY or XX #21 Trisomy Nondisjunction

  16. Down Syndrome Short, broad hands Stubby fingers Rough skin Impotency in males Mentally retarded Small round face Protruding tongue Short lifespan

  17. Turners Syndrome 1 in 5,000 births 45 chromosomes X only #23 MonosomyNondisjunction 96-98% do not survive to birth No menstruation No breast development Narrow hips Broad shoulders and neck

  18. Klinefelter Syndrome 1 in 1,100 births 47 chromosomesXXY only #23 Trisomy Nondisjunction Scarce beard Longer fingers and arms Sterile Delicate skin Low mental ability Normal lifespan

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