Chapter 10 Vocab
Gene
Sequence of DNA that encodes a specific protein or RNA molecule
Allele
one of two or more alternative forms of a gene
Chromosome
A continuous molecule of DNA wrapped around protein in the nucleus of a eukaryotic cell; also, the genetic material of a prokaryotic cell
Diploid Cell
A cell containing two full sets of chromosomes, one from each parent; also called 2n
Autosomes
A nonsex chromosome
Sex Chromosomes
A chromosome that carries genes that determine sex
Homologous Pair
Two chromosomes that look alike and have the same sequence of genes
Meiosis
Division of genetic material that halves the chromosome number and yields genetically variable nuclei
Haploid Cell
A cell containing one set of chromosomes; also called n
Gamete
A sex cell; sperm or egg cell
Fertilization
The union of two gametes
True-Breeding
Always producing offspring identical to the parent for one or more traits; homozygous
Hybrid (genetics)
Producing a mix of offspring for one or more traits; heterozygous
Dominant Allele
Allele that is expressed whenever it is present
Recessive Allele
Allele whose expression is masked if a dominant allele is present
Genotype
An individual’s combination of alleles for a particular gene
Homozygous
Possessing two identical alleles for a particular gene
Heterozygous
Possessing two different alleles for a particular gene
Phenotype
Observable characteristic of an organism
Wild-Type Allele
The most common allele, genotype, or phenotype
Mutant Allele
An allele, genotype, or phenotype that is not the most common in a population or that has been altered from the “typical” (wild-type) condition
P (parental) Generation
The first generation (true-breeding) in a genetic cross
F1 Generation
The offspring of the P generation in a genetic cross
F2 Generation
The offspring of the F1 generation in a genetic cross
Locus
The physical location of a gene on a chromosome
Monohybrid Cross
Mating between two individuals that are heterozygous for the same gene
Punnett Square
Diagram that uses the genotypes of the parents to reveal the possible results of a genetic cross
Test Cross
A mating of an individual of unknown genotype to a homozygous recessive individual to reveal the unknown genotype
Law of Segregation
Mendel’s law stating that the two alleles of each gene are packaged into separate gametes
Dihybrid Cross
Mating between two individuals that are both heterozygous for one gene
Law of independent assortment
Mendel’s law stating that during gamete formation, the segregation of the alleles for one gene does not influence the segregation of the alleles for another gene
Product Rule
The chance of two independent events occurring equals the product of the individual chances of each event
Linked Genes
Genes on the same chromosome
Linkage Group
Group of genes that tend to be inherited together because they are on the same chromosome
Crossing Over
Exchange of genetic material between homologous chromosomes during prophase I of meiosis
Parental Chromatid
Chromatid containing genetic information from only one parent
Recombinant Chromatid
Chromatid containing genetic information from both parents as a result of crossing over
Linkage Map
Diagram of gene order and spacing on a chromosome, based on crossover frequencies
Recombinant Offspring
An individual that inherits a recombinant chromatid
Incomplete Dominance
Mode of inheritance in which a heterozygote’s phenotype is intermediate between the phenotypes of the two homozygotes
Codominance
Mode of inheritance in which two alleles are fully expressed in a heterozygote
Pleiotropy
Multiple, seemingly unrelated phenotypic effects of one genotype
Epistasis
One gene masks the phenotype associated with another gene
Complete Dominance
One allele masks the expression of another in a heterozygote
Sex-Linked
Describes genes or traits on the X or Y chromosome
Y-Linked
Describes traits controlled by genes on the Y chromosome
X-Linked
Describes traits controlled by genes on the X chromosome
X Inactivation
Turning off all but one X chromosome in each cell of a mammal (usually female) early in development
Autosomal Dominant
Inheritance pattern of a dominant allele on an autosome
Autosomal Recessive
Inheritance pattern of a recessive allele on an autosome
Pedigree
Chart showing family relationships and phenotypes
Epigenetics
The study of changes in gene expression that do not involve changes in the DNA sequence
Polygenic
Caused by more than one gene; polygenic traits are typically expressed as a continuum of possible phenotypes