Principle of Gen, Seidler Flashcards
Genes
segment of DNA in chromosome
Locus (loci)
where gene occupies on chromosome
Telomere
region at end of chromosome for stability
Somatic Cells
diploid
differentiated, have a specific destination tissue
Stem cells
undifferentiated cells that can divide into 2 diploid cells
not sure what they will be yet
Homologous chromosomes
pair of chromosomes
Mosaicism
cells from patient have a different genotype (and karyotype)
ex: downs syndrome, klinefelter syndrome, turner syndrome,
Lyonization (X-inactivation)
random choice of which X chromosome is to be inactivated
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
Non-disjunction
failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during divison
Autosomes
chromosomes codon in both genders, one from each parent
Meiosis genetic diversity
Random segregation of homologs
Cross-over exchange
Aneuploid
cells with abnormal chromosome number
Trisomy 21: (down syndrome)
additional 21 (70% in Meiosis 1)Down Syndrome
Trisomy type: 47, XX +21
Robertsonian Translocation: 46, XX der(14:21) +21
Mosaic Type: 46,XX/47,XX+21
Klinefelter Syndrome
47XXY compared to 46XY
extra X chromosome, boy has girl features (lack testosterone, breast growth, little hair)
Turner Syndrome
45X0 compared to 46XX
girl lacking X chromosome
delayed puberty, small stature…
Uniparental Disomy
2 chromosomes from the same parent have parent-specific imprinting = no gene product
ex: Prader Willi, Angelman, Beckwith-Wiedemann
Prader Willi Syndrome
chromosome 15
paternal chromosome is deleted
get both 15’s from mother
Angelman Syndrome
chromosome 15
maternal chromosome is deleted
get both 15’s from father
Beckwith-Wiedemann
chromosome 11 uniparental disomy
Genetic Mechanisms of Disease
Loss of Function = Duchenne Muscular Dystrophy
Gain of Function = Cancer
Protein Alteration = Sickle Cell Anemia
Cystic Fibrosis
individuals with distinct genotypes can have single phenotype (different classes result in CF)
PKU
individuals with same genotype can have multiple phenotypes
very specific defect
Tyr exposure
Phe removal/transportation etc…
Autosomal Dominant
pedigree shows trait in every generation
only 1 allele for trait is needed, 50%
Postaxial Polydactly
Autosomal Recessive
consanguinity more likely to cause occurrence
2 copies of allele is needed for phenotype, 25%
Tyrosinase-negative/deficiency
Albinism
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
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
Penetrance
Frequency that a gene manifests itself
some cases = 100%
some are less
Reduced penetrance
Retinoblastoma (also autosomal dominant)
phenotype occurs in 90% of individuals inheriting the genetic defect (90% penetrance)
Variable expressivity
the range of phenotypes that vary between individuals of a specific genotype
Neurofibromatosis
tumor like growths (Cafe-au-laits spots)
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
Gene Frequency (Allele Frequency)
the proportions of each allele in a population
A or a
Genotype frequency
the proportions of each genotype in a population
AA vs Aa vs aa
Hardy Weinberg Principle
p2 (squared) = AA frequency
q2 (squared) = aa frequency
2pq = Aa frequency
p + q = 1
Multifactorial Disease
caused by simultaneous influence of multiple genetic and environmental factors
