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What are the different types of chromosomal disorders?
- Single gene disorders: autosomal recessive, autosomal dominant, x-linked
- Dominant disorders: mutant gene is clinically expressed and masked normal gene
- Recessive disorders: mutant gene is not clinically expressed
- Multifactoral inheritance: more than one gene is involved and its caused by an interaction of many genes and environmental factors
What are some causes of chromosomal disorders? What is the most significant cause?
- Radiation, drugs, viruses, toxins
- Most significant cause is Maternal age, which significantly increases every year after 35
What is monosomy?
- Absence of a chromosome
- Incompatible with life except sex chromosomes
What is Trisomy? What are three common types?
- Presence of an extra chromosome
- Trisomy 21: down's syndrome
- Trisomy 13: Patau's syndrome
- Trisomy 18: Edward's sydrome
What is mosaicism?
- A mutation that occurs after conception andmost commonly affects the sex chromosomes
- some genes are affects and others are not, leading to a mixing of expressions
- Autosomal is a classic sign of high functioning down's
- Can be either a deletion or additional of chromosome material
What is a Barr Body?
- It is an "extra or unused" x chromosome
- For example, women have XX and 1 barr body
- Men can XY and have no barr body
What is Turner syndrome?
- Female is missing an X chromosome- XO
- No barr body
- Loss of ovarian function and puberty
- Small structure, poor bone development
- Usually diagnosed by age 5
What is XXX?
- Female has an extra barr body
- Increased risk of developmental and motor skill delay
What is Intra Cytoplasmic Sperm injection (ICPI)?
- Sperm injected directly into the ovum
- May increase risk of chromosomal and congenital anomalies due to overriding natural safe guards preventing fertilization
What is autosomal dominant inheritance?
- Affects males and females equally
- If abnormal gene is present the person has the disease
- May be inherited or a new mutation
- 50% chance of passing onto children
What is autosomal recessive inheritance?
- Individuals must have two abnormal genes to be affected
- Affect men and women equally
- Parents can be carriers or have the disease
- Carrier is heterozygous, meaning they have only one abnormal gene and are clinically normal
What is x-linked recessive inheritance?
- Abnormal gene is on the x chromosome
- Female is the carrier and male gets disease
- No male-to-male transfer
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