1. Mendelian Inheritance Flashcards
Law of Segregation
alleles separate into different gametes, each individual has 2 alleles for each trait, one from each parent
Law of Independent Assortment
alleles segregate independently, inheriting one allele doesn’t increase/decrease chance of inheriting another allele, (exception for alleles on same chromosome)
Law of Dominance & Uniformity
traits can be dominant or recessive, need two copies to be recessive, one copy to be dominant, dominant traits mask recessive traits
Monohybrid Cross
crossing two individuals with one trait
Test Cross
crosses a true-breeding recessive individual with an individual that expresses the dominant phenotype, determines if individual is heterozygous or homozygous
Dihybrid Cross
crossing two individuals with two traits, P1 is two true-breeding individuals, F1 are heterozygous, F2 follow 9:3:3:1 inheritance pattern
Product Rule
probability that 2 independent events is the probability of each individual event, multiplied
Pedigree
family tree that tracks a single trait
Autosomal
not sex-linked
Sex-Linked
trait that is present on sex chromosomes
Autosomal Recessive
Examples: Tay-Sachs disease, Cystic Fibrosis, sickle cell anemia, albinism
- typically skips generations
- males/females affected similarly
- 25% prevalence when both parents are heterozygous
Autosomal Dominant
Examples: Huntington’s, neurofibromatosis, achondroplasia, familial hypercholesteremia
- typically does not skip generations
- males/females affected similarly
- affected child MUST have affected parent
- 50% prevalence when one parent is affected
X-Linked Recessive
Examples: Red-green colorblindness, Duchenne muscular dystrophy, Hemophilia A
- typically skips generations
- affects males more than females
- affected fathers do not pass it down to sons, but make their daughters carriers
- affected females must have affected father
- 50% prevalence when one parent is affected
X-Linked Dominant
Examples: Rett Syndrome, Hypophatemic rickets, ornithine transcarbamylase deficiency
- typically does not skip generations
- affects females more than males (has double the chance of inheriting it)
- affected mothers pass it on to their sons
- affected fathers do not pass it on to their sons
- affected fathers pass it down to all daughters
Y-Linked Traits
Examples: hearing loss
- only affects males
- fathers pass it down to all sons
- typically does not skip generations
Pleiotropy
Examples: Marfan syndrome, phenylketonuria
- one gene affects multiple traits
Polygenic Traits
Examples: height, Type 2 Diabetes, most traits/disorders
- multiple genes TOGETHER affect one trait
Genetic Heterogeneity
Examples: predisposition to breast cancer, inherited hearing loss, mental illness
- multiple genes SEPARATELY can affect one trait
Penetrance
the proportion of people in a population who actually develop the trait
Expressivity
the degree to which a trait is expressed
Incomplete Dominance
Examples: heterozygous for familial hypercholesteremia will have intermediate LDL levels
- both phenotypes are represented as a mixed phenotype, “intermediate”
Codominance
Examples: both normal and sickled blood cells in sickle cell anemia
- both phenotypes are expressed equally
Epistasis
Examples: alopecia masks hair color due to baldness
- one gene masks the expression of another gene, one gene acts dominant over the other
Lethal Alleles
Examples: homozygous dominant achondroplasia is lethal
- cannot survive with allele
