Chapter 14: Mendel And The Gene Idea Flashcards
Character
An observable heritable feature that may vary among indiviudals such as flower color
Trait
One of two or more detectable variants in a genetic character such as a purple or white flower
Allele
Any of the alternative versions of a gene that may produce distinguishable phenotypic effects
Dominant allele
An allele that is fully expressed in the phenotype of a heterozygote
Recessive Allele
An allele whose phenotypic effect is not observed in a heterozygote
Homozygote
An organism that has a pair of identical alleles for a gene
Heterozygote
An organism that has two different alleles for a gene
Heterozygous
Having two different alleles for a given gene
The law of Segregation
The two alleles in a pair separate from each other into different gametes during gamete formation
Phenotype
The observable physical and physiological traits of an organism, which are determined by its genetic makeup
Genotype
the genetic makeup, or set of alleles, of an organism
Test Cross
Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype
Monohybrids
An organism that is heterozygous with respect to a single gene of interest
All of the offspring between parents that are homozygous for different alleles are monohybrids
AA + aa = Aa
Monohybrids cross
A cross between two organisms that are heterozygous for the character being followed
Dihybrids
An organism that is heterozygous with respect to two genes of interest.
All of the offspring from a cross between parents doubly homozygous for different alleles are dihybrids
AABB + aabb = AaBb
The law of independent assortment
Each pair of alleles segregates, or assorts, independently of each other pair during gamete formation
Applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome
Multiplication rule
A rule of probability stating that the probability of two or more independent events occurring together can be determined by multiplying their individual probabilities
One event and another
Addition rule
A rule of probability stating that the probability of any one of two or more mutually exclusive events occurring can be determined by adding their individual probabilities.
One event or another
Complete dominance
The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable
Incomplete dominance
The situation in which the phenotype of heterozygote is intermediate between the phenotypes of individuals homozygous for either allele.
Codominance
the situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.
Tay-Sachs Disease
A human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performances usually become manifest a few months after birth, followed by death within a few years
Pleiotropy
The ability of a single gene to have multiple effects
Epistasis
A type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene
Polygenetic Inheritance
An additive effect of two or more genes on a single phenotypic character
Quantitative character
A heritable feature that varies continuously over a range rather than in an either/or fashion.
Multi factorial
Referring to a phenotypic character that is influenced by multiple genes and environmental factors
Pedigree
A diagram of a family read with conventional symbols, showing the occurrence of heritable characters in parents and offspring over multiple generations.
