Genetics Vocabulary
Chromosome thread like structure found in the nucleus.
Chromosome Number total number of chromosomes in nucleus of
each cell - except sex cells e.g. 46 in man, making two matching sets
of chromosomes (23 pairs)
Gamete sex cell – sperm in male animal, egg in female animal. Pollen
grain in male plants, ovule in female plant. Each gamete contains half
the chromosomes of a normal body cell.
Gamete Mother cell cell which divides to from 4 gametes
Fertilization a male gamete and a female gamete fusing (joining)
Zygote a female gamete which has been fertilized by a male gamete
and has 2 matching sets of chromosomes (1 from male parent, 1
from female parent).
Gene a small section of a chromosome carrying information for an
inherited characteristic.
Allele different forms of the same gene e.g. straight wing allele and
curved wing allele in fruit flies.
Homozygous organisms with 2 identical forms of a gene e.g. 2 alleles
for blue eyes
Heterozygous organisms with 2 different forms of a gene e.g. 1
allele for blue eyes and 1 allele for brown eyes.
Genotype the set of genes an organism has.
Phenotype the organisms inherited characteristics resulting from
its genotype
NL 2011
Dominant allele inherited characteristic which is always expressed
in the phenotype if present
Recessive allele inherited characteristic which is only expressed in
the phenotype when there are 2 recessive alleles in the genotype
Cross mating of 2 individuals in order to observe offspring
Monohybrid cross cross involving 1 difference between parents.
Parents (P) original individuals in cross.
First Filial Generation (F1) first offspring of parents in a cross, all
phenotypes are identical and express the dominant characteristic.
Second Filial Generation (F2) offspring resulting from crossing
members of F1. 75% will show dominant characteristic and 25% will
show recessive characteristic.
Phenotypic Ratio proportion of individuals with dominant
characteristics to individuals with recessive characteristic (usually
3:1 in F2)
True Breeding individual which, when mated with an individual of
identical genotype, will always produce offspring identical to itself.
Selective Breeding crosses designed to produce desirable
characteristics e.g. resistance to disease.
Mutation change in chromosome which can be inherited.
NL 2011