Chapter 9
Terms
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- monohybrid cross
- a cross between individuals that involves one pair of contrasting traits
- genotypic ratio
- the ratio of the genotypes that appear in offspring
- phenotype
- an organism's appearance or other detectable characteristic that results from the organism's genotype and the environment
- genetics
- the science of heredity and of the mechanisms by which traits are passed from parents to offspring
- F1 generation
- the first generation of offspring obtained from an experimental cross of two organisms
- genotype
- the entire genetic makeup of an organism; also the combination of genes for one or more specific traits
- dominant
- describes the allele that is fully expressed when carried by only one of a pair of homologous chromosomes
- probability
- the likelihood that a possible future event will occur in any given instance of the event; the mathematical ratio of the number of times one outcome of any event is likely to occur to the number of possible outcomes to the event
- test cross
- the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype
- pollination
- the transfer of pollen from the male reproductive structures (the anthers) to the tip of a female reproductive structure (the pistil) of a flower in angiosperms or to the ovule in gymnosperms
- true-breeding
- describes organisms or genotypes that are homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait
- recessive
- describes a trait or an allele that is expressed only when two recessive alleles for the same characteristic are inherited
- homozygous
- describes an individual that has identical alleles for a trait on both homologous chromosomes
- phenotypic ratio
- the ratio of phenotypes produced by a cross
- cross-pollination
- a reproductive process in which pollen from one plant is transferred to the stigma of another plant
- complete dominance
- a relationship in which one allele is completely dominant over another
- law of independent assortment
- the law that states that genes separate independently of one another in meiosis
- F2 generation
- the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation
- dihybrid cross
- a cross between individuals that have different alleles for the same gene
- allele
- one of the alternative forms of a gene that governs a characteristic, such as hair color
- law of segregation
- Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
- incomplete dominance
- a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully
- self-pollination
- the transfer of pollen grains from an anther to the stigma of the same flower or to the stigma of another flower on the same plant
- molecular genetics
- the study of the structure of nucleic acids and the function and regulation of genes
- Punnett square
- a graphic used to predict the results of a genetic cross
- trait
- a genetically determined variant of a characteristic
- P generation
- parental generation, the first two individuals that mate in a generic cross
- heterozygous
- describes an individual that has two different alleles for a trait
- codominance
- a condition in which both alleles for a gene are fully expressed
- heredity
- the passing of genetic traits from parent to offspring