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Abnormal chromosome diseases
- [1] Caused by error in the number or structure of chromosomes
- [2] Chromosomal abnormalities usually result from an error occurring when an egg or sperm cell develop
- [3] Some chromosomal abnormalities result in miscarriage or stillbirth
- [4] Many children with a chromosomal abnormality have mental and/or physical defects
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Down syndrome
- {1} A genetic condition in which a person has 47 chromosomes instead of the usual 46
- {2} Occurs when there is an extra copy 0f chromosome 21, called trisomy 21
- {3} Incidence is 1 in 800, higher in children born to mothers over age 35
- {4} Life expectancy is relatively short due to complications such as congenital heart disease
- {5} Increased susceptibility to respiratory tract infections
- {6} High incidence of leukemia
- {7} Mental retardation ranges from mild to sever
- {8} Physical development is often slower than normal
- {9} Short stature, never reach average adult height
- {10} Children may have delayed mental and social development
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Down syndrome Treatment
- a} No specific treatment
- {b} Major surgeries to immediately after birth to treat
- <1> Intestinal blockage
- <2> Atrial and/or ventricular septal defects
- <3> Behavioral training
- <4> Special education
- <5> Speech, physical, and occupational therapies
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Cri Du Chat (French for cry of the cat) syndrome
- {1} Also known as 5p- (5p minus) syndrome
- {2} Caused by a missing piece of chromosome 5 that may play a role in control of cell growth
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Sex anomalies
- Chromosome mutations may occur due to exposure to mutagens such as radiation
- [a] Chromosome breakage is a result of one type of mutation
- [b] Broken chromosome fragment may be deleted, duplicated, inverted, or translocated to a non-homologous chromosome
- [c] Mutations occurring during meiosis cause cells to have either too many or too few chromosomes
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Turner syndrome
- {a} One X chromosome is missing (genotype
- is XO)
- {b} Persons appear female, but
- <1> Ovaries do not develop
- <2> No ovulation or menstruation
- <3> Person is sterile
- <4> Mammary nipples widely spaced apart
- <5> Breasts do not develop
- <6> Develop congenital heart disease- coarctation of the aorta
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Klinfelter syndrome
{a} Extra X chromosome (genotype is XXY)
- {b} Person appears male, but
- <1> Testes do not develop
- <2> No sperm production
- <3> Person is sterile
- <4> Breast enlargement and female distribution of hair occurs
- <5> Little facial hair
- <6> Appearance of immature adult
- <7> Person is mentally impaired
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Intersex or disorders of sex development
- hermaphroditism
- Pseudohermaphroditism
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hermaphroditism
- {a} A group of conditions where there is a discrepancy between external (testes) and internal (ovaries) genitalia
- {b} At birth an unambiguous assignment of male or female cannot be made
- {c} Newborn may exhibit both male and female sexual characteristics and organs
- {d} The number of true hermaphrodites is small
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Pseudohermaphroditism
- {a} A state in which an individual has internal reproductive organs of one sex while exhibiting physical characteristics of the opposite sex
- {b} May have either testes or ovaries that are usually nonfunctional
- {c} Sex chromosome differs from anatomic sex and is referred to sex reversal
- {d} In some instances pseudohermaphroditism may be due to excessive sex hormone production from the adrenal cortex
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Genetic
counseling
- [1] Goal is to obtain complete, detailed family history or pedigree from prospective parents
- [2] Pedigree is used to determine pattern of inheritance of a genetic disease within a family
- [3] Diagnosis of genetic diseases
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Two
diagnostic techniques
- Amniocentesis
- Chorionic villi
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Amniocentesis
- Amniotic fluid drawn after the 14 week of pregnancy examining for
- <1> Recovery of fetal cells for analyzing fetal chromosomes
- <2> Examining for biochemical abnormalities in amniotic fluid
- <3> Test results obtained within 2 weeks
- <4> ~200 genetic diseases can be detected before birth
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Chorionic villi
- {a} Projections of the membrane
- surrounding the embryo in early pregnancy
- <1> Involves removing cells from the villi through the cervix
- <2> Samples collected between 8 and 10 weeks of pregnancy to allow time for exploring various options
- <3> Chromosomes can be analyzed immediately
- <4> Results if gender and chromosomal information obtained sooner in the pregnancy
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Gene therapy for genetic diseases
- {1} Involves identification, manipulation, and transference of genetic segments into a host to replace defective genes
- {2} Goal of gene therapy
- {a} Replace a mutated gene that causes disease with a healthy copy of the gene
- {b} Inactivate, or “knocking out”, a mutated gene that is dysfunctional
- {c} Introduce a new gene into the body to help fight a disease
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Congenital diseases
- [1] Disease appearing at birth or shortly afterwards
- [2] Not caused by genetic or chromosomal abnormalities
- [3] Arise from some failure during embryonic development or first 2 months of pregnancy
- [4] Cannot be transmitted to offspring
- [5] Exposure to various factors during first trimester can produce serious defects
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Exposure
to various factors during first trimester can produce serious defects
- [a] Maternal infections
- [b] Inadequate oxygenation
- [c] Drugs
- [d] Malnutrition
- [e] Radiation
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Age-related diseases
- 1] Appearance of disease at birth
- [2] Appearance of disease a few months
- after birth
- [3] Appearance of disease in third or
- fourth decade of life
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[3] Appearance of disease in third or fourth decade of life
- [a] Hemochromatosis
- [b] Huntington’s chorea
- [c] Parkinson’s disease
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Appearance of disease a few months after birth
- [a] Tay-Sachs disease
- [b] Cystic fibrosis
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Age-related diseases
- [a] Phenylcktonuria (PKU)
- [b] Galactosemia
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