4. Variation & Inheritance Flashcards
The differences between different species and differences within a species is known as
Variation
We inherit half of our DNA from
each parent
Characteristics that show discrete variation can be separated into
distinct groups
Characteristics that show continuous variation show
a wide range of values
Height is an example of
continuous variation
Eye colour is an example of
discrete variation
Tongue-rolling ability is an example of
discrete variation
Stem length in flowers is an example of
continuous variation
Variation is possible because
of the different genes we inherit
Characteristics that show discrete variation are controlled by
one gene
Characteristics that show continuous variation are controlled by
more than one gene
When a characteristic is controlled by many genes we say it is
polygenic
Most features of our characteristics are polygenic and show
continuous variation
A Gene is
a section of DNA that codes for the production of a protein
Alleles are
different forms of a gene
A phenotype describes the
physical appearance of a characteristic
A phenotype is always written in
words (eg Brown hair, Blue eyes etc)
A genotype is
the set of genes and organism has for a particular characteristic
A genotype is always written in
letters (eg DD, Dd or dd)
A dominant allele
always appears in the phenotype
Individuals that have 2 of the SAME alleles for a characteristic are known as
Homozygous
Individuals that have 2 DIFFERENT alleles for a characteristic are known as
Heterozygous
The expected F2 phenotypic ratio in a monohybrid cross is
3:1
Actual ratios are not always as expected because
Fertilisation is a random process