Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23...
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Transcript of Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23...
![Page 1: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/1.jpg)
Abnormal Meiosis: Genetic Disorders
![Page 2: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/2.jpg)
Review: Human Chromosomes
There are 46 chromosomes (23 homologous pairs) in each somatic cell
22 pairs of autosomes
1 pair of sex chromosomes XX = Female, XY = Male
Karyotype – picture of chromosomes arranged according to shape and size
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Normal Meiosis
46
23 23
23232323
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Non-disjunction
“not coming apart”
failure of chromosome pairs to separate properly during cell division
produces gametes with 22 or 24 chromosomes
due to a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis
Results in a cell with an imbalance of chromosomes
![Page 5: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/5.jpg)
Abnormal Meiosis I
46
24 22
22222424
ALL 4 Abnormal
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Abnormal Meiosis II
46
23 23
23232224
Sister chromatids fail
to separate
![Page 7: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/7.jpg)
Abnormal Meiosis
If the error occurs in meiosis I, ALL 4 of the gametes will be abnormal
If the error occurs in meiosis II, TWO of the gametes will be normal, and the other 2 gametes will be abnormal.
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Trisomy Examples
Down syndrome (chromosome 21)
Edwards syndrome (chromosome 18)
Patau syndrome (chromosome 13)
Klinefelter syndrome (XXY, XXYY, XXXXY)
![Page 9: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/9.jpg)
Down syndrome
![Page 10: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/10.jpg)
Down Syndrome
1 in 800 live births Mild to moderate intellectual ability Round, full face Short height Large forehead
![Page 11: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/11.jpg)
Down Syndrome
![Page 12: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/12.jpg)
Edwards Syndrome
1 in 4,400 births
XX=80%XY=20%
![Page 13: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/13.jpg)
Edwards Syndrome
• Small head• Developmentally
delayed• Internal organ
abnormalities• 90% die before
5 months of age
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Patau Syndrome
![Page 15: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/15.jpg)
Small headSmall or missing eyesHeart defectsExtra fingersAbnormal genitaliaDevelopmentally delayedMost die a few weeks after birth
Patau Syndrome
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Klinefelter Syndrome
![Page 17: Abnormal Meiosis: Genetic Disorders. Review: Human Chromosomes There are 46 chromosomes (23 homologous pairs) in each somatic cell 22 pairs of autosomes.](https://reader035.fdocuments.net/reader035/viewer/2022062301/56649ed25503460f94be21f2/html5/thumbnails/17.jpg)
Klinefelter Syndrome
1 in 1000 live births Males are sterile Small testes; shortage of
testosterone Breast enlargement, reduced facial
and body hair Some boys are shy and/or have
learning disabilities
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Prenatal testing
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Structural Abnormalities
Mutation: any change to the DNA of a cell Deletions: A portion of the chromosome is
missing or deleted e.g. Wolf-Hirschhorn syndrome, and Jacobsen
syndrome
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Structural Abnormalities
Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material
e.g. Charcot-Marie-Tooth disease type 1A
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Structural Abnormalities
Translocations: When a portion of one chromosome is transferred to another chromosome
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Structural Abnormalities continued…
Inversions: A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted
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Please Complete
Computer activity
Check and Reflect Sheet