INTRODUCTION TO GENETICS
DEFINITION OF TERMS
genetics
scientific study of heredity (the delivery of characteristics
from parent to offspring)
fertilization
process in sexual reproduction in which male and female
reproductive cells (gametes) join to form a new cell
trait
specific characteristics of an individual
hybrid
offspring of crosses between parents with different traits
gene
a factor that is passed from parent to offspring; sequence
of DNA that codes for a protein and thus determines a trait
allele
one of a number of different forms of a gene
principle of dominance
Mendel's second conclusion, which states that some
alleles are dominant and others are recessive
segregation
separation of alleles during formation of the gametes (sex
cells)
gamete
sex cell (i.e. sperm and egg)
probability
likelihood that a particular event will occur
, homozygous
having two identical alleles for a particular gene
heterozygous
having two different alleles for a particular gene
phenotype
physical characteristics of an organism
genotype
genetic makeup of an organism
Punnett square
diagram that can be used to predict the genotype and
phenotype combinations of a genetic cross
independent assortment
one of Mendel's principles that states that genes for
different traits can segregate independently during the
formation of gametes
incomplete dominance
situation in which one allele is not completely dominant
over another allele; Ex. when Mirabilis flowers inherit a red
and white gene and this is expressed as pink flowers.
codominance
situation in which the phenotypes produced by both alleles
are completely expressed; Ex. When a chicken has both
black and white feathers expressed.
multiple allele
a gene that has more than 2 alleles; Ex. the fur color of
rabbits which has one gene with 4 alleles - wild type,
Chinchilla, Himalayan, albino
polygenic trait
trait controlled by two or more genes; Ex. eye color in
humans
homologous
DEFINITION OF TERMS
genetics
scientific study of heredity (the delivery of characteristics
from parent to offspring)
fertilization
process in sexual reproduction in which male and female
reproductive cells (gametes) join to form a new cell
trait
specific characteristics of an individual
hybrid
offspring of crosses between parents with different traits
gene
a factor that is passed from parent to offspring; sequence
of DNA that codes for a protein and thus determines a trait
allele
one of a number of different forms of a gene
principle of dominance
Mendel's second conclusion, which states that some
alleles are dominant and others are recessive
segregation
separation of alleles during formation of the gametes (sex
cells)
gamete
sex cell (i.e. sperm and egg)
probability
likelihood that a particular event will occur
, homozygous
having two identical alleles for a particular gene
heterozygous
having two different alleles for a particular gene
phenotype
physical characteristics of an organism
genotype
genetic makeup of an organism
Punnett square
diagram that can be used to predict the genotype and
phenotype combinations of a genetic cross
independent assortment
one of Mendel's principles that states that genes for
different traits can segregate independently during the
formation of gametes
incomplete dominance
situation in which one allele is not completely dominant
over another allele; Ex. when Mirabilis flowers inherit a red
and white gene and this is expressed as pink flowers.
codominance
situation in which the phenotypes produced by both alleles
are completely expressed; Ex. When a chicken has both
black and white feathers expressed.
multiple allele
a gene that has more than 2 alleles; Ex. the fur color of
rabbits which has one gene with 4 alleles - wild type,
Chinchilla, Himalayan, albino
polygenic trait
trait controlled by two or more genes; Ex. eye color in
humans
homologous
