Chapter 14 Flashcards
‘Particulate’ hypothesis
model in which parents pass down heritable units that retain separate identities in offspring
o Genes can be shuffled and passed along
character
a heritable feature that varies among individuals
trait
each variant for a character
true-breeding
varieties that, over many generations of self-pollination, produce the same variety of parent plant (same phenotype)
hybridization
the crossing of two true-breeding varieties
P generation (true-breeding)
the true-breeding parents
F1 generation (true-breeding)
the hybrid offspring of the P generation
F2 generation (true-breeding)
results when F1 hybrids self-pollinate
alleles
alternative versions of genes
law of segregation
2 alleles for a heritable character segregate during gamete formation and end up in different gametes
testcross
when you breed an organism of an unknown genotype with a recessive homozygote
o This will reveal the genotype of the organism
monohybrids
heterozygous for one particular character in the cross
monohybrid cross
a cross between two heterozygotes for one character
dihybrids
individuals heterozygous for 2 characters in a cross
o Ex: YyRr
dihybrid cross
a cross between F1 dihybrids
law of independent assortment
states that 2 or more genes assort independently; each pair of alleles segregates independently of each other pair of alleles during gamete formation
o This applies only to allele pairs located on different chromosomes or
o Genes very far apart on the same chromosome
multiplication rule
for determining the probability that 2 or more independent events will occur together, multiply the probability of one event by the probability of the other event
o Ex: events occurring on two different chromosomes
addition rule
to find the probability that any 1 of 2 or more mutually exclusive events will occur, add the individual probabilities
complete dominance
when the F1 offspring looks like 1 of the two parental varieties
o Phenotypes of heterozygote and dominant homozygote are indistinguishable
incomplete dominance
when neither allele is completely dominant
o F1 phenotype is somewhere between the 2 parental varieties
o Ex: when R and W flowers produce pink
codominance
when two alleles each affect the phenotype in separate, indistinguishable ways
o Both phenotypes are exhibited by heterozygotes since both molecules are present
o Ex: RR & WW combine to make RW (roan)
Tay-Sachs disease
inherited disorder in which afflicted has brain cells which cannot metabolize certain lipids
o Lipid accumulation results in blindness, seizures, poor motor performance
o Due to incomplete dominance, but codominance at the molecular level
pleitropy
genes which have multiple phenotypic effects
o Responsible for hereditary diseases such as cystic fibrosis and sickle-cell anemia
epistasis
when the phenotypic expression of a gene at a locus alters that of a gene at a second locus
