19 - Simple Mendelian genetics: genes and alleles Flashcards
Gene
A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)
Allele
Any of the alternative versions of a gene that may produce distinguishable phenotypic effects
Genotype
The genetic makeup, or set of alleles, of an organism
Phenotype
the observable physical and physiological traits of an organism, which are determined by its genetic makeup
Homozygote
An organism that has a pair of identical alleles for a gene (encoding a character)
Heterozygote
an organism that has two different alleles for a gene (encoding a character)
Homozygous recessive
refers to having two copies of the same RECESSIVE gene for a particular trait
homozygous dominant
refers to having two copies of the same DOMINANT gene for a particular trait
gamete
A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis. Gametes unite during sexual reproduction to produce a diploid zygote.
Test cross
Breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.
P (parental) generation
the TRUE BREEDING (homozygous) parent individuals from which F1, hybrid off-spring are derived in studies of inheritance. (P stands for parental)
F1 generation
The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross
F2 generation
The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation
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
law of segregation
Mendel’s first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation
True-breeding
Referring to organisms that produce offspring of the same variety over many generations of self-pollination
Law of independent assortment
Mendel’s second law, stating that 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 to behave as though they are on different chromosomes
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.
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.
Monohybrid cross
A cross between two organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant)
Dihybrid cross
A cross between two organisms that are each heterozygous for BOTH of the character being followed (or the self-pollination of a plant that is heterozygous for both characters)
