Inheritance Flashcards
Define genotype
The genetic constitution of an organism
Define phenotype
expression of an organism’s genetic
constitution, combined with its interaction
with the environment
What is an allele?
Different forms of a particular gene,
found at the same locus (position) on a
chromosome
How many alleles per gene do diploid
organisms carry?
Two
What is meant by a dominant allele?
An allele whose characteristic will always
appear in the phenotype, whether one or
two are present
What is meant by a recessive allele?
An allele whose characteristic only
appears in the phenotype if no dominant
allele is present, meaning two must be
present
What is meant by codominant alleles
Two dominant alleles that both contribute
to the phenotype, either by showing a
blend of both characteristics, or the
characteristics appearing together
What is meant by homozygous and
heterozygous?
Homozygous= both alleles are dominant,
or both alleles are recessive.
Heterozygous= one allele is dominant,
the other is recessive
Define monohybrid inheritance
Where one phenotypic characteristic is
controlled by a single gene
Define dihybrid inheritance
Where two phenotypic characteristics
are determined by two different genes
present on two different chromosomes at
the same time
What is meant by sex-linkage?
Where an allele is located on one of the
sex chromosomes, meaning its
expression depends on the sex of the
individual
Why are males more likely to express a
recessive sex-linked allele?
Most sex-linked alleles are located on the X
chromosome. Therefore males only get one
copy of the allele, so will express this
characteristic even if it’s recessive. Since
females get two alleles, this is less likely
What is meant by autosomal linkage?
Where two or more genes are located on the
same (non-sex) chromosome. In this case, only
one homologous pair is needed for all four
alleles to be present. For genes that aren’t
linked, two homologous pairs are needed
What is meant by epistasis?
Where two non-linked genes interact, with
one gene either masking or suppressing
the other gene
What is the chi-squared test?
A statistical test to find out whether the
difference between observed and expected
data is due to chance or a real effect
