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Atypical Meiosis

Atypical Meiosis. BC Science Probe 9 Section 4.5 Pages 127-129. Nondisjunction. Sometimes errors happen during meiosis and the homologous chromosomes do not separate. This is called nondisjunction . Nondisjunction.

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Atypical Meiosis

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  1. Atypical Meiosis BC Science Probe 9 Section 4.5 Pages 127-129

  2. Nondisjunction • Sometimes errors happen during meiosis and the homologous chromosomes do not separate. • This is called nondisjunction.

  3. Nondisjunction • If one of the gametes that fuses during fertilization has the wrong number of chromosomes, the zygote will have either too much or too little genetic information.

  4. Nondisjunction • For example: • If a gamete with 22 chromosomes fuses with a gamete with 23, the zygote will have 45 instead of 46. • Most of the time this causes the zygote to not divide and it dies.

  5. Down Syndrome • Down syndrome (DS), also called Trisomy 21, is a condition in which extra genetic material causes delays in the way a child develops, both mentally and physically.

  6. Down Syndrome • Down Syndrome affects about 1 in 800 babies born. • Heart conditions, hearing loss and hypothyroidism are common among people with Down Syndrome.

  7. Patau Syndrome • Trisomy 13, also called Patau syndrome, is a chromosomal condition associated with severe intellectual disability and physical abnormalities in many parts of the body.

  8. Patau Syndrome • Individuals with trisomy 13 often have heart defects, brain or spinal cord abnormalities, very small or poorly developed eyes, extra fingers and/or toes, a cleft lip or a cleft palate, and weak muscle tone.

  9. Turner Syndrome (X0) • Most girls are born with two X chromosomes, but girls with Turner syndrome are born with only one X chromosome or they are missing part of one X chromosome.

  10. Turner Syndrome (X0) • Short stature • Lack of sexual development • a low hairline at the back of the neck • drooping of the eyelids • differently shaped ears that are set lower • abnormal bone development • a larger than usual number of moles on the skin • extra fluid in the hands and feet

  11. Trisomic X (XXX) • XXX syndrome (also called Trisomy X or Triple X) is caused by the presence of an extra ‘X’ chromosome in every cell.

  12. Trisomic X (XXX) • Tall stature (height) • Possible mild facial characteristics • Normal IQ, but may be 10-15 points below siblings • Speech and language delays (50%) • poor coordination • introverted, difficulty with interpersonal relationships

  13. Klinefelter Syndrome (XXY) • Affected individuals typically have small testes that do not produce as much testosterone as usual. • A shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement, reduced facial and body hair, and an inability to have biological children (infertility).

  14. Klinefelter Syndrome (XXY) • Children with Klinefelter syndrome may have learning disabilities and delayed speech and language development. • They tend to be quiet, sensitive, and unassertive, but personality characteristics vary among affected individuals.

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