Chapter 14 - Mendel and the Gene Idea
Terms
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- Character
- heritable features that vary among individuals
- Trait
- each variant for a character (such as purple or white flowers)
- Hybridization
- the mating or crossing of two varieties
- Monohybrid cross
- the term for a cross that tracks the inheritance of a single character
- Alleles
- alternative versions of a gene
- Law of segregation
- the separation of alleles into separate gametes
- Homozygous
- a term used to describe organisms having a pair of identical alleles for a character
- Heterozygous
- a term used to describe organisms having two different alleles for a gene
- Phenotype
- an organism’s appearance
- Genotype
- an organism’s genetic makeup
- Law of independent assortment
- the independent segregation of each pair of alleles during gamete formation
- Incomplete dominance
- a condition in which the F1 hybrids have an appearance somewhere in between the phenotypes of the two parental varieties
- Complete dominance
- a condition in which the phenotypes of the heterozygote and the dominant homozygote are indistinguishable
- Codominance
- a condition in which both alleles are separately manifest in the phenotype
- Pleiotropy
- the ability of a gene to affect an organism in many ways
- Epistasis
- a condition in which a gene at one locus alters the phenotypic expression of a gene at a second locus
- Quantitative characters
- genetic characters that vary in the population along a continuum
- Polygenic inheritance
- an additive effect of two or more genes on a single phenotypic character; converse of pleiotrop
- Norm of reaction
- the product of a genotype is generally not a rigidly defined phenotype, but a range of phenotypic possibilities over which there may be variation due to environmental influence
- Multifactorial characters
- a term used to describe characters in which many factors, both genetic and environmental, collectively influence phenotype
- Pedigree
- a family tree describing the interrelationships of parents and children across generations for a particular trait
- Carrier
- a person who is phenotypically normal but are heterozygous for a certain disorder and, thus, may transmit the recessive allele to offspring
- Cystic fibrosis
- the most common lethal genetic disease in the United States; membrane chloride channels are defective or absent in those with both recessive alleles for this trait
- Sickle-cell disease
- the most common inherited disease among blacks; caused by the substitution of a single amino acid in the hemoglobin protein of red blood cells