Chapter 14: Mendel Flashcards
character
heritable feature that varies among individuals
trait
variant for a character
true breeding
offspring have the same phenotype
hybridization
crossing of two true-breeding varieties
P generation
true breeding parent generation
F1 generation
hybrid offspring of P generation
F2 generation
offspring of F1 hybrids
Mendel’s Model
- alleles cause variation in characters
- two copies of a gene, one from each parent, are inherited for each character
- dominant allele determines phenotype over recessive allele
- law of segregation
allele
alternative versions of a gene
law of segregation
two alleles segregate during gamete formation so each gamete has only one of two alleles
homozygous
identical alleles for a gene
heterozygous
two different alleles for a gene
phenotype
appearance
genotype
genetic makeup
testcross
cross of homozygous organism with organism of unknown genotype
monohybrids
heterozygous for one character
dihybrid
heterozygous for two character
law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
independent events
unaffected by other events
multiplication rule
calculate the probability that 2+ more independent events will occur together by multiplying individual probabilities
mutually exclusive events
events that cannot occur together
addition rule
probability that any one of 2+ mutually events will occur is calculated by adding individual probabilities
complete dominance
dominant allele completely masks recessive allele
incomplete dominance
neither allele is completely dominant
codominance
each allele affects phenotype in separate, distinguishable ways
Tay-Sachs disease
inherited disorder where brain cells cannot metabolize certain lipids, causing seizures, blindness, death.
pleiotropy
one gene has multiple phenotypic effects
epistasis
phenotypic expression of a gene at one locus alters that of a gene at a second locus
quantitative characters
vary in population in gradations along a continuum
polygenic inheritance
2+ genes affect one character
norm of reaction
phenotypic range for a genotype
multifactorial
many factors, environmental + genetic, affect phenotype
pedigree
family tree describing traits of parents + children across generations
carriers
heterozygotes that have recessive gene but are phenotypically normal
cystic fibrosis
genetic disease with defective chloride transport channels in plasma membranes. causes thicker mucus. recessive
sickle-cell disease
substitution of valine for glutamic acid in hemoglobin causing blood cells to have sickle shape. recessive
huntington’s disease
dominant genetic disorder. degenerative disease of nervous system that only appears at 35-45 years old.
amniocentesis
physician inserts needle and extracts 10 mL amniotic fluid in 14th-16th week of pregnancy.
chorionic villus sampling
physician inserts narrow tube through cervix into uterus and suctions out sample of tissue from placenta
phenylketonuria (PKU)
cannot properly digest amino acid phenylalanine, which accumulates to toxic levels in the blood -> retard
