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Flashcards in Principle of Gen, Seidler Deck (35):
1

Genes

segment of DNA in chromosome

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Locus (loci)

where gene occupies on chromosome

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Telomere

region at end of chromosome for stability

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Somatic Cells

diploid

differentiated, have a specific destination tissue

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Stem cells

undifferentiated cells that can divide into 2 diploid cells

not sure what they will be yet

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Homologous chromosomes

pair of chromosomes

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Mosaicism

cells from patient have a different genotype (and karyotype)

ex: downs syndrome, klinefelter syndrome, turner syndrome,

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Lyonization (X-inactivation)

random choice of which X chromosome is to be inactivated

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Cell Cycle

Interphase-
G1: Cell growth and differentiation

S: synthesis of DNA, duplication of chromosomes

G2: cell growth and prep for cell division

Mitotic cell division
prophase, metaphase, anaphase, telophase, cytokinesis

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Non-disjunction

failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during divison

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Autosomes

chromosomes codon in both genders, one from each parent

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Meiosis genetic diversity

Random segregation of homologs

Cross-over exchange

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Aneuploid

cells with abnormal chromosome number
Trisomy 21: (down syndrome)
additional 21 (70% in Meiosis 1)

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Down Syndrome

Trisomy type: 47, XX +21

Robertsonian Translocation: 46, XX der(14:21) +21

Mosaic Type: 46,XX/47,XX+21

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Klinefelter Syndrome

47XXY compared to 46XY

extra X chromosome, boy has girl features (lack testosterone, breast growth, little hair)

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Turner Syndrome

45X0 compared to 46XX

girl lacking X chromosome
delayed puberty, small stature...

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Uniparental Disomy

2 chromosomes from the same parent have parent-specific imprinting = no gene product

ex: Prader Willi, Angelman, Beckwith-Wiedemann

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Prader Willi Syndrome

chromosome 15

paternal chromosome is deleted
(get both 15's from mother)

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Angelman Syndrome

chromosome 15

maternal chromosome is deleted
(get both 15's from father)

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Beckwith-Wiedemann

chromosome 11 uniparental disomy

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Genetic Mechanisms of Disease

Loss of Function = Duchenne Muscular Dystrophy
Gain of Function = Cancer
Protein Alteration = Sickle Cell Anemia

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Cystic Fibrosis

individuals with distinct genotypes can have single phenotype (different classes result in CF)

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PKU

individuals with same genotype can have multiple phenotypes

very specific defect
Tyr exposure
Phe removal/transportation etc...

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Autosomal Dominant

pedigree shows trait in every generation

only 1 allele for trait is needed, 50%

Postaxial Polydactly

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Autosomal Recessive

consanguinity more likely to cause occurrence

2 copies of allele is needed for phenotype, 25%

Tyrosinase-negative/deficiency
Albinism

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X-linked Recessive

unaffected males don't transmit, never carriers

female carriers can transmit 50% sons and daughters

all daughters of affected males are heterozygous carriers

Duchenne Muscular Dystrophy

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X-linked Dominant

rare, no carriers

affected males transmit 100% only to females

Hypophosphatemia
leads to Rickets in children
soft bone, bad absorption of Ca and phosphate

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Penetrance

Frequency that a gene manifests itself
some cases = 100%
some are less

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Reduced penetrance

Retinoblastoma (also autosomal dominant)

phenotype occurs in 90% of individuals inheriting the genetic defect (90% penetrance)

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Variable expressivity

the range of phenotypes that vary between individuals of a specific genotype

Neurofibromatosis
tumor like growths (Cafe-au-laits spots)

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Locus Heterogenity

single disorder, trait, or pattern of traits caused by mutations in genes at different chromosome loci

Osteogenesis Imperfecta
brittle bone disease
mutations in 7 and 17 loci, either produces this disease

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Gene Frequency (Allele Frequency)

the proportions of each allele in a population

A or a

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Genotype frequency

the proportions of each genotype in a population

AA vs Aa vs aa

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Hardy Weinberg Principle

p2 (squared) = AA frequency

q2 (squared) = aa frequency

2pq = Aa frequency

p + q = 1

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Multifactorial Disease

caused by simultaneous influence of multiple genetic and environmental factors