Genetics
Genetics Terminology
Gene A section of DNA strand is called a gene
Pairs of genes on homologous chromosomes. 1
gene may code for the blue eyes and the other for
Alleles
brown eyes, i.e alternative forms of the same
gene
Genes that code for the same characteristics on
Locus homologous pairs of chromosomes are found in
the same place (Locus) on a chromosome
A crossing where the researcher is interested in
Monohybrid only one gene pair, i.e. only 1 characteristic eg,
crossing
eye / flower colour
The outward, physical appearance of the
Phenotype individual for a particular gene pair, e.g. blue eyes
The actual gene combination a person has on her
Genotype homologous chromosomes, e.g. heterozygous for
brown eyes
To work out the genotype of an individual - is it
heterozygous or homozygous for the dominant
Test cross
trait ? cross the organism with a recessive
phenotype
, This means that the pair of genes, alleles, are
coding for the same form of a particular
Homozygous
characteristic, e.g. blue eyes (bb) or brown eyes
(BB)
The pair of genes on the homologous
chromosomes code for a different form of a
Heterozygous
particular characteristic, eg. blue and brown eyes
(Bb)
A gene capable of producing its characteristic in
the Phenotype even if only one gene is present,
eg. if brown eyes are dominant over blue - a
Dominant
person will have brown eyes whether she is
homozygous (BB) or heterozygous (Bb) for brown
eye colour
Can only produce their phenotype if the individual
is homozygous for that characteristic. These
Recessive genes genes are represented by small letters of the
same type as the dominant gene, eg. blue eyes
(bb)
P1 Parent generation
F1 First generation of offspring
F2 The second generation of offspring when two F1
are crossed
Genetics Terminology
Gene A section of DNA strand is called a gene
Pairs of genes on homologous chromosomes. 1
gene may code for the blue eyes and the other for
Alleles
brown eyes, i.e alternative forms of the same
gene
Genes that code for the same characteristics on
Locus homologous pairs of chromosomes are found in
the same place (Locus) on a chromosome
A crossing where the researcher is interested in
Monohybrid only one gene pair, i.e. only 1 characteristic eg,
crossing
eye / flower colour
The outward, physical appearance of the
Phenotype individual for a particular gene pair, e.g. blue eyes
The actual gene combination a person has on her
Genotype homologous chromosomes, e.g. heterozygous for
brown eyes
To work out the genotype of an individual - is it
heterozygous or homozygous for the dominant
Test cross
trait ? cross the organism with a recessive
phenotype
, This means that the pair of genes, alleles, are
coding for the same form of a particular
Homozygous
characteristic, e.g. blue eyes (bb) or brown eyes
(BB)
The pair of genes on the homologous
chromosomes code for a different form of a
Heterozygous
particular characteristic, eg. blue and brown eyes
(Bb)
A gene capable of producing its characteristic in
the Phenotype even if only one gene is present,
eg. if brown eyes are dominant over blue - a
Dominant
person will have brown eyes whether she is
homozygous (BB) or heterozygous (Bb) for brown
eye colour
Can only produce their phenotype if the individual
is homozygous for that characteristic. These
Recessive genes genes are represented by small letters of the
same type as the dominant gene, eg. blue eyes
(bb)
P1 Parent generation
F1 First generation of offspring
F2 The second generation of offspring when two F1
are crossed
