Karyotypes and Mutations Karyotype



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Karyotypes and Mutations

Karyotype

  • An orderly display of magnified images of the individual’s chromosomes
  • Shows the chromosomes as they appear in metaphase.

What is a Normal Karyotype?

  • We are supposed to have 46 total chromosomes in each cell (22 pairs of autosomes = 44, + 2 sex chromosomes).

Amniocentesis

Preparing a Karyotype

  • 1. Use blood cells.

Essay: Preparing a Karyotype

  • 2. Burst RBC (red blood cells-have no nucleus) in hypotonic solution.
  • Release WBC (white blood cells).

Essay: Preparing a Karyotype

  • Use a centrifuge to separate the white blood cells from the rest of the blood fluid
  • centrifuge

Preparing a Karyotype

  • 4. Add chemical (colchicine) to stop the chromatids in metaphase (stops spindle fibers from forming)
  • making a karyotype video

Preparing a Karyotype (cont)

  • 5. Drop on a slide.

Preparing a Karyotype (cont)

  • 5. Take a picture
  • 6.Sort by size and shape from largest to smallest

Types of Karyotypes

  • Fluorescent to detect a marker showing certain defect
  • karyotype procedure video 4:29

Types of Karyotypes

  • Ideogram: bands locate sites on chromosome

Normal Karyotype

  • WHY?
  • Is it a Male or a female?

Down Syndrome Karyotype

  • Trisomy 21
  • Due to nondisjunction (chrom did not
  • separate evenly)

Down Syndrome

  • Trisomy 21
  • Folds over eyes
  • Sluggish muscles
  • Mental Problems
  • (IQ often below 50)- but
  • Some much higher

Down Syndrome

Down Syndrome

  • Short Stature
  • heart defects
  • susceptibility to respiratory infection , leukemia, ADHD,
  • Alzheimer’s
  • We Are More ALike Than Different (2:40)

Does the mother’s age matter?

  • As the age of the mother increases above 30, the frequency of Trisomy 21 also increases

Abnormal Sex Chromosomes

  • 47 XXY syndrome
  • male
  • testes small (sterile)
  • breast enlargement
  • feminine body contours (wider hips)
  • 1 in 500 to 1,000 newborn males
  • Klinefelter’s

Klinefelter’s Syndrome

  • also XXYY, XXXY, XXXXY

TURNER SYNDROME

  • XO (only one X)
  • Short
  • often web of skin between neck and shoulders
  • sterile
  • poor breast development

Turner Karyotype

What about…

  • MUTATIONS?

Chromosomal Mutations

  • most often brought on by problems that occur during meiosis or by mutagens (chemicals, radiation, etc.) = cancer-causing agent
  • Often harmful

Can you find the changes?

DELETION

Duplication

  • Fragment of one chromosome attaches to a homologous chromosome
  • Maybe no harm.

Translocation

  • Fragment reattaches in reverse direction (less likely to produce harm)

Translocation

INVERSION

Inversions

  • Inversions, by definition, do not involve loss or gain of chromosomal material.
  • chromosomal mutations (Mcgraw Hill)
  • Click mutations

INVERSION

Staining Chromosomes

  • Chromosomes from the father of a child... a portion of chromosome 11 (blue) has been transferred to chromosome 1(yellow).


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