53 terms

AP Biology Test Prep Chapter 10: Heredity-Terms

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Law of Segregation
Genetic principle that states that every organism carries factors, called alleles, for each trait, and the members of the pair separate during the formation of gametes.
Law of Independent Assortment
Genetic principle that states that each pair of factors are distributed independently when the gametes are formed.
Law of Dominance
Genetic principle that states that when two opposite pure-breeding varieties of an organism are crossed, all of the offspring resemble one parent.
Allele
A variant of a gene for a particular character.
Genotype
An organism's genetic makeup for a given trait.
Heterozygous
An individual has two alleles that are different for a single gene (Bb).
Homozygous
An individual has two alleles that are the same for a single gene (BB or bb).
Karyotype
A chart that organizes chromosomes in relation to number, size, and type.
Phenotype
The physical expression of the trait associated with a particular genotype.
Character
A heritable feature, such as flower color, that varies among individuals.
"Blending Hypothesis"
Theory that the genes contributed by two parents mix as if they are paint colors and the exact genetic makeup of each parent can never be recovered.
Monohybrid Cross
A cross that involves a single character in which both parents are heterozygous/hybrids that results in a 3:1 phenotype ratio.
Dihybrid Cross
The crossing of two hybrids for two different characters that gives a 9:3:3:1 phenotype ratio.
Test Cross
Crossing of an organism of unknown dominant genotype with an organism that is homozygous recessive for the trait, resulting in offspring with observable phenotypes which is used to determine an unknown genotype.
Intermediate Inheritance
Genetic principle that states that an individual heterozygous for a trait shows characteristics not exactly like those of either parent. The phenotype is either a middle genotype of both of the parents' genetic input or an expression of both parental genotypes.
Incomplete Dominance
Genetic principle that states that in the heterozygous genotype neither allele dominates the other and the phenotype is intermediate.
Hypercholesterolemia
Recessive disorder that causes cholesterol levels to be many times higher than normal and can lead to heart attacks in children as young as two years old.
Codominance
Genetic principle that states that both alleles express themselves fully in a heterozygous organism.
Polygenic Traits
Traits that are affected by more than one gene.
Epistasis
Genetic principle that states that a gene at one locus alters the phenotypic expression of a gene at another locus. A dihybrid cross involving these genes produces a 9:4:3 phenotype ratio.
Pleiotropy
Genetic principle that states that a single gene has multiple effects on an organism.
Autosomal Chromosome
Chromosome that is not directly involved in determining gender.
Wild-Type Phenotype
The normal phenotype for a characteristic in organisms.
Mutant Phenotype
Characters that are not the normal strain in organisms.
Duchenne's Muscular Dystrophy
Sex-linked disorder caused by the absence of an essential muscle protein that leads to the progressive weakening of the muscles combines with a loss of muscle coordination.
Hemophilia
Sex-linked disorder caused by the absence of a protein vital to the clotting process. Individuals with this condition have difficulty clotting blood after even the smallest of wounds.
Red-Green Colorblindness
Sex-linked condition that leaves those afflicted unable to distinguish between red and green colors.
X Inactivation
During the development of the female embryo, one of the two X chromosomes in each cell remains coiled as a Barr body whose genes are not expressed. A cell expresses the alleles of the active X chromosome only.
Barr Body
Inactivated genes on an X chromosome.
Holandric Traits
A trait inherited via the Y chromosome.
Linked Genes
Genes along the same chromosome that tend to be inherited together because the chromosome is passed along as a unit.
Linkage Map
A genetic map put together using crossover frequencies.
Map Unit
A unit to geographically relate genes on the basis of crossover frequencies.
Law of Multiplication
Law that states that to determine the probability that two random events will occur in succession, you simple multiply the probability of the first event by the probability of the second event.
Pedigrees
Family trees used to describe the genetic relationships within a family.
Tay-Sachs Disease
A fatal genetic storage disease that renders the body unable to break down a particular type of lipid.
Cystic Fibrosis
A recessive disorder that is the most common lethal genetic disease in the United States, in which a defective version of a gene on chromosome 7 results in the excess secretion of a thick mucus, which accumulates in the lungs and digestive tract.
Sickle Cell Anemia
A recessive disease caused by the substitution of a single amino acid in the hemoglobin protein of red blood cells, leaving hemoglobin less able to carry oxygen and also causing the hemoglobin to deform to a sickle shape when the oxygen content is low.
Hemoglobin
Molecule that allows red blood cells to carry and deliver oxygen throughout the body to hard-working organs and tissue.
Phenylketonuria
An autosomal recessive disorder caused by a single gene defect that leaves a person unable to break down phenylalanine, which results in a by-product that can accumulate to toxic levels in the blood and cause mental retardation.
Huntington Disease
An autosomal dominant degenerative disease of the nervous system that shows itself when a person is in their 30s or 40s and is both irreversible and fatal.
Aneuploidy
The condition of having an abnormal number of chromosomes.
Down Syndrome
An aneuploid syndrome affecting one out of every 700 children born into the United States; often involves a trisomy of chromosome 21; and leads to mental retardation, heart defects, short stature, and characteristic facial features.
Patau Syndrome
The presence of trisomy 13, which causes serious brain and circulatory defects.
Edwards Syndrome
The presence of trisomy 18, and affects almost every organ of the body.
Klinefelter Syndrome
Syndrome in which individuals have male sex organs but are sterile, display several feminine body characteristics, and have sex chromosomes XXY.
Turner Syndrome
Affects females who are missing an X chromosome.
Chromosomal Deletion
When a piece of the chromosome is lost in the developmental process.
Cri-du-chat Syndrome
This syndrome occurs with a deletion in chromosome 5 that leads to mental retardation, unusual facial features, and a small head.
Chromosomal Translocation
Condition in which a piece of one chromosome is attached to another, nonhomologous chromosome.
Chronic Myelogenous Leukemia
A cancer affecting white blood cell precursor cells. In this disease, a portion of chromosome 22 has been swapped with a piece of chromosome 9.
Chromosomal Inversion
Condition in which a piece of a chromosome separates and reattaches in the opposite direction.
Chromosomal Duplication
Error in chromosomal replication that results in the repetition of a genetic segment.