Download STAAR REVIEW—GENETICS, NATURAL SELECTION

STAAR REVIEW—GENETICS, NATURAL SELECTION, &
ARTIFICIAL SELECTION/ SELECTIVE BREEDING —CATEGORY 4
 Genetics: The study of heredity
 Gregor Mendel: The father of genetics
 Alleles: Genes that code for different versions of a trait (represented by capital
and lower case letters)
 Chromosomes: Specific location of the inherited traits (genes) in our cells
 Phenotype: The physical appearance of an individual (ex: green eyes, tongue
roller, hitchhikers thumb, blood type, etc.)
 Genotype: The actual alleles a person has in order to get a specific phenotype;
Represented by capital and lowercase letters (ex: TT, Tt, or tt)
 Dominant: Alleles in which the traits always show up—They mask other traits;
Represented with a capital letter (ex: T=hitchhikers thumb)
 Recessive: Alleles in which the traits are masked by dominant alleles—They only
show up if paired with another recessive allele (ex: t=regular thumb)
 Homozygous: Two of the same alleles (ex: TT (homozygous dominant) or tt
(homozygous recessive—only way recessive phenotype will show up in
offspring)).
 Heterozygous: Two different alleles (ex: Tt (Dominant allele masks recessive
allele in this case, so dominant phenotype will still show up)
 Natural Selection: Nature “selects” which individuals will survive—those with the
best characteristics/those who are better adapted to their environment (ex:
Green bugs show up more on tree bark than brown bugs and therefore have less
chance for long-term survival and die out quicker); “Survival of the Fittest”
 Charles Darwin: Noted for his research on Natural Selection—specifically on the
Galapagos Islands (ex: varying beak structure in finches—suited for that they eat)
 Artificial Selection: Humans select (not nature) individuals with desired traits and
breed them; “selective breeding” (ex: breeding of dogs)
1. Ears of corn weren’t always as big as they are now (Humans crossed them
until the current size became most abundant/common)
2. Carrots weren’t always orange—Long ago, they were purple, yellow, and
white (Humans took “rare” orange carrots and crossed them until
eventually they became most commonly grown color)
3. Percherons—Horses that were bred to do heavy work (Humans crossed
horses that were bigger/stronger to produce a new breed)