ABERRATIONS.ppt
- 2. Chromosomes • contain units of heredity (genes) • composed of chromatin (DNA + protein) • organisms contain a specific number of chromosomes
- 3. Karyotyping • determines the number and structure of chromosomes in the cell nucleus • can be used to detect chromosomal aberrations
- 4. NON-DISJUNCTION •Failure of chromosomes to separate during anaphase of mitosis or meiosis.
- 5. A. Variations in the chromosome number 1. Aneuploidy • Addition or loss of one or more chromosomes • Trisomy (2N+1), monosomy (2N-1) 2. Polyploidy • Addition of chromosome sets • Triploidy (3N), tetraploidy (4N) Chromosomal aberrations changes in the chromosomes (mutations)
- 6. B. Alterations in the chromosome structure 1. Deletion – loss of part of a chromosome 2. Duplication – segment of a chromosome is repeated 3. Inversion – part of a chromosome is oriented in the reverse of its usual direction 4. Reciprocal translocation – part of a chromosome breaks off and attaches to another, non-homologous chromosome
- 7. A B C D E F G H A B C E F G H A B C D E F G H A B C B C D E F G H A B C D E F G H A D C B E F G H A B C D E F G H M N O P Q R A B P Q R M N O C D E F G H Identify the type of alteration that has occurred.
- 8. SOMATIC MOSAICISM • When some cells in an individual have a mutant version of gene while other cells in the same have a normal version of the same gene. • Hemophilia, blood clotting disorder
- 9. CANCER CELLS •Cells that grow out of control.
- 11. TUMORS • BENIGN (non-cancerous) • Grow locally and do not spread. • MALIGNANT (cancerous) • have the ability to spread and invade other tissues • METASTASIS: the process whereby cancer cells break free from a tumor and travel to and invade other tissues in the body.
- 12. Aneuploidy in humans • Trisomies in Autosomes 1. Trisomy 21: Down Syndrome (47, 21+) 2. Trisomy 18: Edwards Syndrome (47, 18+) 3. Trisomy 13: Patau Syndrome (47, 13+) • Aneuploidy of Sex Chromosomes 1. Turner Syndrome (45, XO) 2. Klinefelter Syndrome (47, XXY)
- 13. TRISOMY 21 (47, 21+): DOWN SYNDROME • Most common single cause of birth defects in humans • 1/660 births • Prominent facial features (upward slanting eyes, open mouth with tongue protrusion) • Simian crease in palm (one horizontal line only) • Mental retardation that ranges from mild to severe • Congenital heart defects • Increased susceptibility to many diseases • Mostly sterile • Shorter life span • Increased risk with older mothers
- 14. Trisomy 18: Edwards Syndrome • Second most common autosomal trisomy after trisomy 21. • 1/6000-8000 live births • Severely affects ALL organ systems • Approximately 95% of conceptions with trisomy 18 die in embryonic or fetal life; • The high mortality rate is usually due to the presence of cardiac and renal malformations, feeding difficulties. • Severe psychomotor and growth retardation are invariably present for those who survive beyond infancy.
- 15. TRISOMY 13: PATAU SYNDROME • 1/5000 live births • Multiple abnormalities, many of which are not compatible with more than a few months of life. • Severe mental defects and defects of the brain that lead to seizures, apnea, deafness, and eye abnormalities. • Most infants have a cleft lip and cleft palate, polydactyly and low-set ears. • Congenital heart disease is present in approximately 80% of affected infants. • Because of the severity of congenital defects, life-sustaining procedures are generally not attempted.
- 16. MONOSOMY X (45, XO): TURNER SYNDROME The only known viable monosomy in humans 1/2000 live female births (and 15% of spontaneous abortions) Phenotypically female Sterile, short stature, webbed neck, immature sex organs, secondary sexual characteristics fail to develop, “shield”-type chest (broad and flat)
- 17. Klinefelter Syndrome: 47, XXY • Approximately 1 in 500-1,000 males is born with an extra sex chromosome; • About 40% of conceptions with Klinefelter syndrome survive the fetal period. • In general, severity of somatic malformations in Klinefelter syndrome is proportional to the number of additional X chromosomes; mental retardation and hypogonadism • Mortality rate is not significantly higher than in healthy individuals. Tall stature – thin build and disproportionately long arms and legs
Editor's Notes
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