Ch. 14 - Mendel & the Gene Idea Flashcards
A heritable feature that varies among individuals
Character
Each variant for a character
Trait
Plants who, over many generations of self-pollination, have produced only the same variety of the parental plant
True-breeding
The mating (or crossing) of two true-breeding varieties for different traits
Hybridization
Parental generation
P generation or P1 generation
First filial generation
F1 generation
Second filial generation
F2 generation
Alternate versions of a gene
Alleles
The allele that controls the phenotype of a heterozygote
Dominant allele
The allele in a heterozygote with no noticeable phenotypic effects
Recessive allele
The two alleles for a heritable character segregate during gamete formation and end up in different gametes
Law of Segregation
A handy diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup
Punnett Square
An organism that has a pair of identical alleles for a gene encoding a character
Homozygote
Having a pair of identical alleles for a gene encoding a character
Homozygous
An organism that has two different alleles for a gene
Heterozygote
Having two different alleles for a gene
Heterozygous
An organism’s appearance or observable traits
Phenotype
An organism’s genetic makeup
Genotype
Breeding an organism of unknown genotype with a recessive homozygote
Testcross
All the F1 progeny produced in crosses of true-breeding parents following one trait
Monohybrids
A cross between heterozygotes for one trait
Monohybrid cross
The F1 plants produced in a cross between two true-breeding varieties differing for two traits being observed
Dihybrids
A cross between dihybrids
Dihybrid cross
Two or more genes assort independently - that is, each pair of alleles segregates independently of any other pair of alleles - during gamete formation
Law of Independent Assortment
To determine the probability of multiple events, multiply the probability of one event by the other(s) to see the probability of the total event
Multiplication rule
The probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities
Addition rule
Genes having multiple phenotypic effects
Pleiotropy
Characters that vary along a continuum
Quantitative characters
Degree of dominance in which one allele completely controls the phenotype of the heterozygote
Complete dominance
In which neither allele shows through in the heterozygote, but a new, intermediate phenotype does
Incomplete dominance
Degree of dominance in which both alleles each affect the phenotype in separate, distinguishable ways
Codominance
An inherited disease in humans that expresses incomplete dominance; the brain cells of a homozygote cannot metabolize certain lipids
Tay-Sachs Disease
The phenotypic expression of a gene at one locus alters that of a gene at a second locus
Epistasis