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HLTH 335: CHAPTER 5
DNA
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The blueprint for directing activities
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Chromosomes
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Assembled strands of DNA within the nucleus
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How many autosomes
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44 or 22 pairs
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Female Chromosomes
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XX
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Male Chromosomes
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XY
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Karyotype
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the complete chromosomal composition
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Where are chromosomes extracted from
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nucleus
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Karyotypes detect
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abnormalities |
Genes
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correspond with a particular trait & occupy a particular site on a chromosome
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How many copies of each gene?
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2- one from each parent
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Alleles
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Alternate forms of a gene
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Homozygus
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Alleles are the same (BB or bb)
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Heterozygous
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Different alleles (Bb)
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Dominant alleles
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When only one allele is needed to express a trait (Bb is brown)
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Recessive alleles
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When 2 alleles are needed to express a trait (ex: red hair)
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Autosomal Dominant Diseases
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Transmitted through dominant alleles
Offspring have 50% chance of being affected
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Examples of Autosomal dominate diseases
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Polydactyly
Achondroplasia
Marfan Syndrome
Familial hypercholsetolemia
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Polydactyly
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Additional finger or toe
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Achondroplasia
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Abnormal cartilage formation & long bones
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Marfan Syndrome
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Cartilage grows longer b/c fibrillin is missing
(ex: Lincoln)
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Familial hypercholesterolemia
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high cholesterol running in a family
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Autosomal Recessive Diseases
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Disease manifests when individual is homozygous for defective alleles
Heterozygous parents are carriers
Child has 25% of infection
Usually in close intermarriages
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Examples of Autosomal Recessive
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PKU
Sickle Cell Animia
Falactosemia
Tay-Sachs
Albinism
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PKU-Phenylketonuria
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missing Phenylanine
Derivatives build up and affect brain development
Synthetic diet reduces risk
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Sickle cell anemia
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Blacks most at risk
Deformed RBC
Increases resistance to malaria
Heterozygus just gets mild anemia
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Malaria kills how many a year?
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2 Million
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How many blacks are carriers for sickle cell anemia?
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1 in 12
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Sex-Linked Inheritance
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Defective gene on X chromosome
Expressed in males
Heterozygous female is carier
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Males transmit defective sex-linked alleles to
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Daughers
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More likely to inherit x-linked diseases
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males
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Carrier females for sex-linked
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50% passing it to offspring
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Affected Males with sex-linked
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Only pass to his daughters
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Colorblindess
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inability to distinguish colors, specifically btwn red & green
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Colorblindess occurs
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1 in 10 men
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Hemophilia
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Inactivation of an intrinsic clotting factor that causes bleeding for longer period of time than normal
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Abnormal chromosome diseases
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1. Altered # or structure
2. Failure of chromosome to separate during cell division
3. Complete loss of autosome
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Down Syndrome
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Trisomy of small chromosome
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Incidence of Downs
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1 out of 800
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Incidence of Downs live births
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1 of 100
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Risks of Downs
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Advancing maternal age
1 in 50 if mom >40
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Downs complication
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Sleep apnea, obesity, GI blockage, thyroid problems, early menopause, seizures, hearing loss, premature aging, skeletal problems, poor vision
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% of DS die in utero
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70-75%
15%- before 1
35%- before 50
50%-beyond 50
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Examples of Abnormal Chromosome Disorders
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Cri Du Chat
Turners
Klinefelters
Hermaphrodites
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Pedigree
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complete detailed family history
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amniocentesis
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small amount of amniotic fluid is withdrawn after 14th week to see genome
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Amniocentisis can detect
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~200 genetic diseases
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Gene therapy
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identification, manipulation, & transference of genetic segments into a host to replace defective genes and preform desired genetic activities
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gene therapy aka
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genetic engineering
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What % of newborns have recognizable at birth
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2-3%
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What % of miscarriages have malformation
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25-50%
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Category A
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No risk to fetus demonstrated in human studies
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Category B
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No evidence of risk to fetus. Animals-risk, Humans-no risk OR no adequate human studies
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Category C
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Risk cannot be ruled out. No human studies. Animal studies either not available or possible risk
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Category D
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Risk to fetus, but drug is necessary, & + outweighs -
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Category X
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contridicated in pregnancy, severe risk to fetus outweighs benefit to patient
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