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31 terms

Chapter 9 - Modern Biology

STUDY
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Heredity
the transmission of characteristics from parents to offspring
Trait
a genetically determined variant of a characteristic
Mendel
the scientist who performed tests on pea plants and discovered dominant and recessive traits
Pollination
occurs when pollen grains from the anthers are transferred to the stigma
Anthers
the male reproductive parts of a flower
Stigma
the female reproductive parts of a flower
Self Pollination
when pollination occurs between the stigma and anthers of the same flower or plant
Cross Pollination
when pollination occurs between the stigma and anthers of different plants and flowers
True Breeding
pure - always produce offspring with their traits when they self pollinate
F1 Generation
the offspring of the P generation - all purple pea pod flowers
F2 Generation
the offspring of the F1 generation - 3:1 ratio of purple to white
Dominant
a trait that masks the factor for the other trait in a pair
Recessive
a trait that is masked by the other trait in a pair
Law of Segregation
states that a pair of factors is separated during the formation of gametes
Law of Independent Assortment
states that factors separate independently from one another during the formation of gametes
Molecular Genetics
the study of the structure and function of chromosomes and genes
Allele
two or more alternative forms of a gene
Genotype
the genetic appearance of an organism
Phenotype
the physical appearance of an organism
Homozygous
both alleles of a trait are alike - ex. RR
Heterozygous
the alleles of a trait are different - ex. Rr
Probability
the likelihood that a specific event will occur
Monohybrid Cross
a cross where only one characteristic is tracked
Punnett Square
a diagram that aids in the tracking of distribution of traits to offspring
Genotypic Ratio
the ratio of the genotypes that appear in offspring - ex. 1 BB : 2 Bb : 1 bb
Phenotypic Ratio
the ratio of the offspring's phenotypes - ex. 3 black : 1 brown
Testcross
a test which determines a genotype of an unknown parent with one that is homozygous recessive (rr)
Complete Dominance
occurs when one allele is completely dominant over the other trait - ex. PP and Pp both express the same trait because P is dominant over p
Incomplete Dominance
occurs when the phenotype of a heterozygote is intermediate between dominant and recessive - ex. A flower with the genotype RR is red and a flower with the genotype rr is white. A flower with the genotype Rr is pink.
Codominance
occurs when both alleles for a gene are expressed in a heterozygous offspring - ex. A boy with the genotype BB has brown eyes. A boy with the genotype bb has green eyes. A boy with the genotype Bb has brown and green speckled eyes.
Dihybrid Cross
a cross in which two characteristics are tracked in a punnett square