allele		an organism's gene combination
double helix		heterozygous individual that appears phenotypically the same as a homozygous dominant individual, but which has a recessive allele for an undesirable trait
gamete		reproductive pattern in which haploid gametes fuse to produce a diploid zygote, which then develops by mitosis into a new organism
autosome		cell division in which one diploid (2n) cell produces four haploid (n) cells called sex cells
codominant alleles		fusion of male and female gametes
sex-linked trait		offspring produced when two varieties of plants or animals, or closely related species, are mated
pedigree		mating between closely related individuals to produce pure lines
recessive		exchange of genetic material by non-sister chromatids during late prophase I of meiosis, resulting in new combinations of alleles
messenger RNA		process in which the order of bases in mRNA codes for the order of amino acids in protein
sexual reproduction		inheritance pattern in which the phenotype of the heterozygote is intermediate between those of the two homozygotes
point mutation		mutation affecting gene distribution to gametes during meiosis, most commonly by deletions, insertions, inversions, or translocations
polygenic inheritance		error in the DNA sequence that affects only a single base pair
codon		component of DNA or RNA along with a sugar and a phosphate group
heterozygous		in a flower, the process of transfer of pollen grains from the anther to the stigma
sperm		equal expression of both alleles
testcross		inherited trait controlled by genes located on the sex chromosomes
fertilization		breeding technique used to determine whether an individual is homozygous dominant or heterozygous for a particular trait
phenotype		error in the DNA sequence that adds or deletes a single base, causing nearly all amino acids following the mutation to be changed
heredity		having identical alleles for a particular trait
transfer RNA		Mendelian principle explaining the disappearance of a specific trait in the F1 generation and its reappearance in the F2 generation
trisomy		gene form for each variation of a trait of an organism
dominant		structures having a common evolutionary origin
monosomy		having nonidentical alleles fro a particular trait
hybrid		passing on of characteristics from parents to offspring
genetic recombination		failure of homologous chromosomes to separate during meiosis, resulting in gametes with too few or too many chromosomes
homologous chromosome		male and female sex cells
genetics		branch of biology that studies heredity
haploid		the process by which enzymes make an RNA copy of a DNA strand
multiple alleles		hidden trait of an organism that is masked by a dominant trait
crossing over		absence of a chromosome
transcription		male sex cell
genotype		carries protein synthesis information from DNA to the ribosomes
inbreeding		visible, observable trait of an organism that masks a recessive form of the trait
meiosis		a cell with two copies of each type of chromosome (2n)
trait		the RNA that composes ribosomes
nitrogen base		inherited characteristic
frameshift mutation		in the genetic code, the set of three nitrogen bases representing a specific amino acid
law of independent assortment		female sex cell or gamete
pollination		major source of genetic variation resulting from crossing over or random assortment
nondisjunction		graphic representation showing patterns of inheritance in a family or breeding group
zygote		in humans, the 23rd pair of chromosomes, which controls the inheritance of sex characteristics and differs males from females
diploid		fertilized egg
homozygous		random error or change in the DNA sequence that may affect whole chromosomes or just one gene
translation		presence of an extra chromosome
carrier		presence of more than two alleles for a given genetic trait in a species
mutation		in humans, the 22 matching homologous chromosomes
dihybrid cross		process in which the two strands of the double helix separate and bases pair with free nucleotides to form two molecules of DNA, each identical to the original molecule
chromosomal mutation		outward appearance of an organism, regardless if its genes
replication		delivers amino acids to the ribosome for protein synthesis
incomplete dominance		in DNA, the two twisted, ladder-shaped nucleotide strands held together by hydrogen bonds between the bases
ribosomal RNA		determination of a given trait, such as skin color or height, produced by the interaction of many genes
egg		fertilization between two organisms to study the inheritance of two different traits
sex chromosome		Mendelian principle explaining that different traits are inherited independently if on different chromosomes
law of segregation		a cell of an organism that has half the number of chromosomes (n)