Genetics
Study of biologic inheritance
Chromatin
Substance giving the nucleus a granular appearance, forms chromosomes
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Genetics
Study of biologic inheritance
Chromatin
Substance giving the nucleus a granular appearance, forms chromosomes
Down Syndrome is trisomy?
Trisomy 21
Down syndrome is what?
Autosomal aneuploidy
Down syndrome characteristics
Down syndrome affects what sexes?
Both sexes affected equally
Turner syndrome is what?
Sex aneuploidy
Turner syndrome characteristics?
Turner syndrome affects what sex?
Females only
Klinefelter syndrome is what?
Sex aneuploidy
Klinefelter syndrome characteristics?
Klinefelter affects what sex?
Males only
Cri du chat syndrome is what?
Autosomal deletion (of chromosome 5)
Cri du chat syndrome characteristics?
Cri du chat syndrome affects what sex?
Both sexes
Autosomal dominant diseases?
Autosomal aneuploidy diseases?
Down syndrome (trisomy 21)
Sex chromosome aneuploidy diseases?
*X is always dominant here
Autosomal recessive diseases?
Sex-linked inheritance/X-linked recessive diseases?
Hemophilia
Locus
Position of a gene
Gene
Unit of heredity
Alleles
Variation of a gene
Homozygous dominant
AA
Heterozygous dominant
Aa
Homozygous recessive
aa
How many pairs of chromosomes?
23
How many total chromosomes?
46
How many autosomes?
22 autosomes
How many pairs of sex chromosomes?
1 pair (either XX or XY)
Aneuploidy
The presence of, or absence of one or more chromosomes; does not contain a multiple of 23 chromosomes
Monosomy
Presence of only one copy of any chromosome
*LETHAL
Trisomy
A cell containing 3 copies of one chromosome
Nondisjunction
Cause of an aneuploidy, failure to separate properly during mitosis/meiosis
Penetrance
Percentage of individuals with a specific genotype with expected phenotype; the probability of a trait being expressed
Incomplete penetrance
Individual who has a gene for a disease but does not express the disease
Expressivity
Extent of variation in a phenotype associated with a genotype; variation in phenotypic expression
Autosomal dominant diseases do not…
Skip generations
Huntington disease traits
*Autosomal dominant
Neurofibromatosis traits?
*Autosomal dominant
Consanguinity
Mating of 2 related individuals
Cystic fibrosis traits
*Autosomal recessive
Sickle cell disease traits?
*Autosomal recessive
Hemophilia traits?
*X-linked
X-Linked disorders differences?
*Are recessive disorders
*AFFECTED MOTHER --> SON
*AFFECTED FATHER --> ALL DAUGHTERS AFFECTED
Autosomal recessive diseases do…
Skip generations and have carriers
Autosomal recessive disease parents?
Both parents are usually heterozygous carriers
*Recurrence risk is ~25% for offspring
Recurrence risk
The probability that an individual will develop a genetic disease
*Ex: Autosomal dominant, 1 parent affected, 1 parent normal = 1/2 for each child