DNA and Genetics Vocabulary
Vocabulary Word
DNA
Double Helix
Definition
Deoxyribonucleic acid
Hereditary material that controls all the activities of the cell
The structure of DNA. DNA is composed of two strands of
nucleotides, which form bonds with each other as rungs in a
ladder. These linked strands then twist around one another to
make a helix structure (like a twisted ladder).
Genes
Segments of DNA that carry hereditary instructions and are
passed from parent to offspring
Alleles
Different forms of a single gene. A human genotype often has 2
alleles for each trait.
Dominant trait
The trait observed when at least one dominant allele for a
characteristic is inherited
Recessive trait
A trait that is apparent only when two recessive alleles for the
same characteristic is inherited
Hereditary
Traits that are inherited from a parent by an offspring
Genotype
The inherited combination of alleles (genes).
Phenotype
An organism’s inherited physical appearance, depending on the
genotype.
Homozygous
A “purebred” genotype in which the organism has two of the same
alleles for a particular trait. For example, if you have two browneye genes and no blue eye genes.
DNA and Genetics Vocabulary
Heterozygous
A “hybrid” genotype, in which an organism carries two different
alleles for the same trait. For example, if you have brown eyes,
but also carry a blue-eyed gene, then you are heterozygous for eye
color.
Mutation
A change in the order of bases in an organism’s DNA; deletion,
insertion or substitution. Can happen spontaneously or can be due
to a mutagen. Can be harmful, helpful, or have no effect on the
phenotype.
Mutagen
Anything that can damage or cause changes in DNA
nucleotide
A subunit of DNA consisting of a sugar, a phosphate, and one of
the four nitrogen bases.
Nitrogen Bases
Adenine, thymine, cytosine, and guanine (A-T, C-G). These four
bases make up the DNA “alphabet” and the order of these bases in
the DNA determines the characteristics of the organism.
Co-Dominance
Occurs when both alleles show through to contribute to the
phenotype
Incomplete Dominance
Occurs when one allele is not completely dominant over the other
allele, the result is a mixture between the two alleles
Genetic Engineering
The manipulation of genes that allows scientists to put genes from
one organism into another organism
Selective Breeding
The breeding of organisms that have a certain desired trait
Pedigree
A diagram of family history used for tracing a trait through
several generations